UNCONVENTIONAL PHASE HEXAGONAL PRUSSIAN BLUE ANALOGS WITH OPEN STRUCTURES

Abstract

The present invention relates to a facile synthetic method to synthesize novel hexagonal phase CuCo (HCuCo) PBAs with high crystallinity, as well as extended synthesis of doping PBAs with hexagonal phase: Fe.sub.0.1CuCo, Fe.sub.0.2CuCo, Co.sub.0.1CuCo, Ni.sub.0.1CuCo, and Zn.sub.0.1CuCo. The hexagonal phase HCuCo PBAs and the doping sequence of PBAs with hexagonal phase exhibit superior crystallinity and significantly higher intrinsic specific surface area. Meanwhile, HCuCo PBAs show great potential for gas adsorption and have a positive impact on the development of PBAs for other applications.

Claims

1. A hexagonal phase copper-cobalt Prussian blue analog material, comprising: 30-40 wt % of copper; 10-30 wt % of cobalt; 10-30 wt % of carbon; and 10-30 wt % of nitrogen, wherein each copper ion is coordinated with four cyanogen groups showing a plane quadrilateral configuration, while each copper ion is connected with six cyanogen groups showing an octahedral configuration.

2. The hexagonal phase copper-cobalt Prussian blue analog material of claim 1, wherein the hexagonal phase copper-cobalt Prussian blue analog material is capable of forming prism-shaped crystals.

3. The hexagonal phase copper-cobalt Prussian blue analog material of claim 1, wherein the hexagonal phase copper-cobalt Prussian blue analog material has a 20 value of 13.9, 14.4, 16.0, 20.1, 21.7, 22.1, 23.2, 25.1, 25.5, 26.2, 29.1, 29.9, 31.1, 32.4, 36.1, 37.1, 37.9, 38.8, 39.5, 40.8, 41.7, 44.9, 45.8, 46.2, 47.1, 50.2, 51.6, 52.4, 53.2, 53.9, 55.3, 57.5, 57.8, 58.9, 61.2, 61.7, 62.9, 64.0.

4. The hexagonal phase copper-cobalt Prussian blue analog material of claim 1, wherein the hexagonal phase copper-cobalt Prussian blue analog material exhibits stacking disorders in a hexagonal lattice structure.

5. The hexagonal phase copper-cobalt Prussian blue analog material of claim 1, wherein the hexagonal phase copper-cobalt Prussian blue analog material has a surface area of at least 1000 m.sup.2 g.sup.1.

6. The hexagonal phase copper-cobalt Prussian blue analog material of claim 1, wherein the hexagonal phase copper-cobalt Prussian blue analog material has larger channels and interstitial spaces for metal-ion storage and diffusion.

7. The hexagonal phase copper-cobalt Prussian blue analog material of claim 1, wherein the hexagonal phase copper-cobalt Prussian blue analog material exhibits three types of pores with half pore widths of 2.74, 4.30, and 6.16 .

8. The hexagonal phase copper-cobalt Prussian blue analog material of claim 1, wherein numerous unsaturated copper sites are present within a framework of hexagonal phase copper-cobalt.

9. The hexagonal phase copper-cobalt Prussian blue analog material of claim 8, wherein numerous Cu.sup.I and a low coordination number of CuNCCo are presented in hexagonal phase copper-cobalt Prussian blue analog material.

10. The hexagonal phase copper-cobalt Prussian blue analog material of claim 1, wherein the hexagonal phase copper-cobalt Prussian blue analog material demonstrates a gas adsorption performance that is at least 1.5 times higher than that of cubic PBAs.

11. The hexagonal phase copper-cobalt Prussian blue analog material of claim 10, wherein the gas comprises CO.sub.2, CH.sub.4, C.sub.2H.sub.2, C.sub.2H.sub.4, C.sub.2H.sub.6, C.sub.3H.sub.6, and C.sub.3H.sub.8.

12. The hexagonal phase copper-cobalt Prussian blue analog material of claim 1, wherein the hexagonal phase copper-cobalt Prussian blue analog material demonstrates superior separation performance for C.sub.3H.sub.6/C.sub.2H.sub.4 and CO.sub.2/CH.sub.4 compared to a cubic Prussian blue analog material.

13. The hexagonal phase copper-cobalt Prussian blue analog material of claim 1, wherein the hexagonal phase copper-cobalt Prussian blue analog material is further doped with one or more metal precursors.

14. The hexagonal phase copper-cobalt Prussian blue analog material of claim 13, wherein the one or more metal precursors comprise FeCl.sub.3, NiCl.sub.2, or ZnCl.sub.2, or their hydrates.

15. A method for synthesizing hexagonal phase copper-cobalt Prussian blue analog material, comprising: adding DI water containing CuCI.sub.2.Math.2H.sub.2O, and sodium citrate into a mixed solution of DI water and DMF dissolved K.sub.3Co(CN).sub.6 and PVP to obtain a first solution; continuously stirring the first solution for 24-48 hours in a 30 C. water bath; centrifugating the first solution and collecting precipitate; rinsing collected precipitate with DI water and ethanol for at least 3 times; and drying the collected sample at 80 C. for 10-15 hours.

16. The method of claim 15, wherein the method requires neither high-temperature treatment nor any other post-treatment.

17. The method of claim 15, wherein the hexagonal phase copper-cobalt Prussian blue analog material is capable of forming prism-shaped crystals.

18. The method of claim 15, the first solution further comprises one or more metal precursors.

19. The method of claim 18, wherein the one or more metal precursors comprise FeCl.sub.3, NiCl.sub.2, or ZnCl.sub.2, or their hydrates.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Embodiments of the invention are described in more details hereinafter with reference to the drawings, in which:

[0028] FIG. 1 shows conventional cubic PBA with traditional vacancies engineering and novel hexagonal phase PBA by phase engineering (all water molecules and counter cations are omitted for clarity);

[0029] FIG. 2 shows a synthesis diagram of HCuCo;

[0030] FIG. 3A depicts XRD patterns of HCuCo and CCuCo. FIG. 3B shows three-dimensional electron diffraction patterns. FIG. 3C depicts XPS for Co element and Cu element.

[0031] FIG. 3D depicts XPS spectrums for HCuCo and CCuCo;

[0032] FIG. 4A depicts 1H NMR spectrum of solution after KCl exchanged of HCuCo.

[0033] FIG. 4B depicts TGA curves of HCuCo and CCuCo;

[0034] FIG. 5A shows a SEM image of HCuCo. FIG. 5B shows a SEM image of HCuCo.

[0035] FIG. 5C shows TEM images of HCuCo. FIG. 5D shows a SEM image of CCuCo. FIG. 5E shows a TEM image of CCuCo. FIG. 5F shows a SAED image along the [110] zone axis.

[0036] FIG. 5G shows HRTEM image taken from the white squared marked area in FIG. 5C, inset shows the corresponding Fast Fourier Transform (FFT) result. FIG. 5H shows a side view of the lattice structure of HCuCo. FIG. 5I shows HAADF-STEM image and elements mapping for Cu, Co, C, N;

[0037] FIG. 6A depicts EDS spectrum of HCuCo. Insets are the detail element ratios. FIG. 6B depicts EDS spectrum of CCuCo. Insets are the detail element ratios;

[0038] FIG. 7A shows SEM images of Fe.sub.0.1CuCo, Fe.sub.0.2CuCo, Co.sub.0.1CuCo, Ni.sub.0.1CuCo and Zn.sub.0.1CuCo. FIG. 7B shows TEM images of Fe.sub.0.1CuCo, Fe.sub.0.2CuCo, Co.sub.0.1CuCo, Ni.sub.0.1CuCo and Zn.sub.0.1CuCo. FIG. 7C shows HAADF-STEM images of Fe.sub.0.1CuCo, Fe.sub.0.2CuCo, Co.sub.0.1CuCo, Ni.sub.0.1CuCo and Zn.sub.0.1CuCo. FIG. 7D shows XRD patterns of Fe.sub.0.1CuCo, Fe.sub.0.2CuCo, Co.sub.0.1CuCo, Ni.sub.0.1CuCo and Zn.sub.0.1CuCo;

[0039] FIG. 8 depicts XPS spectra for Cu element of Co.sub.0.1CuCo, Fe.sub.0.1CuCo, Fe.sub.0.2CuCo, Ni.sub.0.1CuCo and Zn.sub.0.1CuCo;

[0040] FIG. 9 depicts XDR patterns before and after heating at 100 C. under vacuum condition for HCuCo and CCuCo;

[0041] FIG. 10A depicts N.sub.2 adsorption-desorption isotherms at 77 K of HCuCo and CCuCo. FIG. 10B depicts pore size distribution of HCuCo and CCuCo. FIG. 10C depicts gas sorption isotherms performances at 273 and 298 K, 1 bar for CO.sub.2, CH.sub.4, C.sub.2H.sub.2, C.sub.2H, C.sub.2H.sub.6, C.sub.3H.sub.6 and C.sub.3H.sub.8 of HCuCo and CCuCo;

[0042] FIG. 11 depicts column breakthrough experiments of C.sub.3H.sub.6/C.sub.2H.sub.4 for HCuCo and CCuCo;

[0043] FIG. 12 depicts experimental column breakthrough curves of CO.sub.2/CH.sub.4 separations for HCuCo and CCuCo;

[0044] FIG. 13A depicts BET test results of Fe.sub.0.1CuCo, Fe.sub.0.2CuCo and Co.sub.0.1CuCo. FIG. 13B depicts CO.sub.2 sorption performance of Fe.sub.0.1CuCo, Fe.sub.0.2CuCo and Co.sub.0.1CuCo. at 273 and 298 K. FIG. 13C depicts CH.sub.4 sorption performance of Fe.sub.0.1CuCo, Fe.sub.0.2CuCo and Co.sub.0.1CuCo. at 273 and 298 K. FIG. 13D depicts CH.sub.4 sorption performance of Fe.sub.0.1CuCo, Fe.sub.0.2CuCo and Co.sub.0.1CuCo. at 273 and 298 K. FIG. 13E depicts C.sub.2H.sub.4 sorption performance of Fe.sub.0.1CuCo, Fe.sub.0.2CuCo and Co.sub.0.1CuCo. at 273 and 298 K. FIG. 13F depicts C.sub.2H.sub.6 sorption performance of Fe.sub.0.1CuCo, Fe.sub.0.2CuCo and Co.sub.0.1CuCo. at 273 and 298 K. FIG. 13G depicts C.sub.3H.sub.6 sorption performance of Fe.sub.0.1CuCo, Fe.sub.0.2CuCo and Co.sub.0.1CuCo. at 273 and 298 K. FIG. 13H depicts C.sub.3H.sub.8 sorption performance of Fe.sub.0.1CuCo, Fe.sub.0.2CuCo and Co.sub.0.1CuCo. at 273 and 298 K;

[0045] FIG. 14A depicts XANES spectrum of HCuCo, CCuCo and the reference materials. FIG. 14B depicts Fourier transform spectra derived from EXAFS of HCuCo, CCuCo and the reference materials. FIG. 14C depicts WT-EXAFS spectrum of Co element for HCuCo, CCuCo, K.sub.3Co(CN).sub.6 and Co foil. FIG. 14D depicts corresponding WT-EXAFS of Cu element for HCuCo, CCuCo, Cu.sub.2O, CuO and CuPc; and

[0046] FIG. 15A depicts EXAFS fitting for Co element, K space and R space data and fitting results of HCuCo are shown. FIG. 15B depicts EXAFS fitting for Co element K space and R space data and fitting results of CCuCo are shown. FIG. 15C depicts EXAFS fitting for Cu element, K space and R space data and fitting results of HCuCo are shown. FIG. 15D depicts EXAFS fitting for Cu element, K space and R space data and fitting results of CCuCo are shown.

DETAILED DESCRIPTION

[0047] In general, existing PBAs are fcc structure with low specific surface area and defect-rich features, which may limit the application development for PBAs. Cubic phase Prussian blue and its analogs are coordination compounds that remain stable under room temperature and pressure. PBAs hold great potential in various fields. Nevertheless, the randomly distributed defects and intrinsic characteristics of conventional cubic PBAs pose challenges to their study and development.

[0048] Therefore, the present invention provides a hexagonal phase copper-cobalt Prussian blue analog material, which includes 30-40 wt % of copper, 10-30 wt % of cobalt, 10-30 wt % of carbon and 10-30 wt % of nitrogen. Each copper ion is coordinated with four cyanogen groups showing a plane quadrilateral configuration, while each copper ion is connected with six cyanogen groups showing an octahedral configuration. The open-framework structure of PBAs includes channels and interstitial spaces that facilitate the rapid diffusion of various carrier ions and small molecules. The invention of hexagonal phase PBAs (e.g., hexagonal phase HCuCo PBAs) not only provides a significantly higher specific surface area but also larger open channels and interstitial spaces. This allows for a greater capacity to store ions and small molecules, as well as quicker diffusion and release rates for carriers.

[0049] In one embodiment, the hexagonal phase copper-cobalt Prussian blue analog material is capable of forming prism-shaped crystals. In addition to prism-shaped crystals, the hexagonal phase copper-cobalt Prussian blue analog material can also form the following crystal shapes: rhombic crystals, hexagonal prismatic crystals, octahedral crystals, etc.

[0050] The hexagonal phase HCuCo PBAs exhibit crystal structures with a plane configuration of Cu atoms. X-ray absorption fine structure analysis reveals numerous unsaturated Cu sites within the framework of HCuCo.

[0051] The high crystalline H-CuCo PBAs deliver a much higher specific surface area of at least 1000 m.sup.2 g.sup.1.

[0052] Preferably, the high crystalline H-CuCo delivers a much higher specific surface area of 1273.24 m.sup.2 g.sup.1.

[0053] The high crystalline H-CuCo PBA achieves approximately 1.5 times gas adsorption performance than conventional cubic CuCo PBA. In particular, the CO.sub.2 uptake capacity of the HCuCo shows 6.09 and 4.18 mmol g.sup.1 (at 273 K and 298 K, 1 bar).

[0054] The HCuCo PBAs also show a much better gas separation performance of C.sub.3H.sub.6 to C.sub.2H.sub.4 for 2 times of separation coefficient than cubic CuCo PBA and a breakthrough of CO.sub.2/CH.sub.4 separation. Such impressive performance should be attributed to the large number of unsaturated copper sites in the framework of HCuCo PBAs.

[0055] In another aspect, the present invention provides a method for preparing HCuCo PBAs with hexagonal phase, including: [0056] adding DI water containing CuCl.sub.2.Math.2H.sub.2O, and sodium citrate into a mixed solution of DI water and DMF dissolved K.sub.3Co(CN).sub.6 and PVP to obtain a first solution; [0057] continuously stirring the first solution for 24-48 hours in a 30 C. water bath; centrifugating the first solution and collecting precipitate; [0058] rinsing collected precipitate with DI water and ethanol for at least 3 times; and drying the collected sample at 80 C. for 10-15 hours.

[0059] In another aspect, the present invention provides doped HCuCo PBAs with hexagonal phase, which are made by feeding few amounts of different metal precursor. Large-scale production is feasible by proportionally increasing the concentrations of precursors, indicating high potential for industrial-level production of novel hexagonal phase HCuCo PBAs.

[0060] In another aspect, the present invention provides a method for preparing doped HCuCo PBAs with hexagonal phase, including: adding DI water containing CuCl.sub.2.Math.2H.sub.2O, precursors of metal chlorides, and sodium citrate into a mixed solution of DI water and DMF dissolved K.sub.3Co(CN).sub.6 and PVP to obtain a first solution; continuously stirring the first solution for 24-48 hours in the 30 C. water bath; collecting the precipitate by centrifugation; rinsing the collected precipitate with DI water and ethanol for at least 3 times, respectively; and drying the collected sample at 80 C. for 10-15 hours.

[0061] In one embodiment, the precursors of metal chlorides may be FeCl.sub.3, NiCl.sub.2, or ZnCl.sub.2, or their hydrates.

[0062] In one embodiment, the concentration of the concentration of the precursors of metal chlorides is less than 0.04 mmol.

[0063] In one embodiment, the concentration of the sodium citrate is in a range 0.1-0.5 mmol.

[0064] In one embodiment, the ratio between DI water and DMF of the mixed solution is 2:5.

[0065] In summary, a facile and low-cost method is developed to prepare a novel hexagonal phase CuCo Prussian blue analogue (PBA) with a large amount of unsaturated Cu atoms through phase engineering. Using 3D electronic diffraction, the hexagonal lattice structure of HCuCo can be confirmed, in which Cu ions with four cyano groups over N adopt a planar, four-sided configuration, while Co ions with six cyano groups over C form an octahedral configuration, resulting in the formation of a 12-ring pore channel. In contrast to conventional cubic structure CuCo PBAs, this hexagonal PBA exhibits significantly enhanced CO.sub.2 adsorption performance and improved adsorption capabilities for CH.sub.4, C.sub.2H.sub.2, C.sub.2H.sub.4, C.sub.2H, C.sub.3H.sub.6, and C.sub.3H.sub.8. Furthermore, HCuCo PBAs demonstrates superior separation performance for C.sub.3H.sub.6/C.sub.2H.sub.4 compared to cubic PBAs and represents a breakthrough in CO.sub.2/CH.sub.4 separation.

[0066] Additionally, verified by XPS and XAFS tests, a large amount of Cu.sup.I and a low coordination number of CuNCCo are found in HCuCo PBAs, which is attributed to its unconventional hexagonal phase. This indicates that many Cu atoms in HCuCo PBAs are unsaturated and in an open state. This is likely the reason why HCuCo PBAs exhibit significantly better performance. In addition, a series of CuCo PBAs with a hexagonal phase dopant are developed. This doping strategy allows for the modulation of both morphology and the quantity of unsaturated Cu atoms.

[0067] In the following description, specific details are provided to offer a comprehensive understanding of the present invention, for explanatory purposes and not intended for limitation.

Example

Example 1

Materials and Methods

[0068] Potassium hexacyanocobaltate (K.sub.3Co(CN).sub.6, 99%), polyvinylpyrrolidone (PVP, molecular weight 58,000), cobalt chloride hexahydrate (CoCl.sub.2.Math.6H.sub.2O, AR), copper chloride dihydrate (CuCl.sub.2.Math.2H.sub.2O, AR), nickel chloride hexahydrate (NiCl.sub.2.Math.6H.sub.2O, AR), zinc chloride (ZnCl.sub.2, ACS Grade) and sodium citrate (Na.sub.3C.sub.6H.sub.5O.sub.7, AR, 99%) were purchased from Shanghai Aladdin. Ferric chloride hexahydrate (FeCl.sub.3.Math.6H.sub.2O, AR) were purchased from Dieckmann. Ethanol (ACS Grade, absolute) was purchased from Anaqua Global International Inc. Limited. Dimethylformamide (DMF, AR) was purchased from the RCl Labscan. All the chemicals and materials were used as received without any further purification.

Characterization

[0069] Synthesized samples were identified by the X-ray diffractometer (XRD) (SmartLab, 40 kV) with K rays radiated from Cu. The scanning electron microscope (SEM) samples were prepared by dropping the suspension solution onto the silicon substrate and dried under ambient conditions. The SEM images were collected on a QUATTRO S SEM operated at 20 kV. The transmission electron microscope (TEM) images were acquired on JEOL JEM-2100F. Thermogravimetry analysis (TGA) measurements were conducted on the PerkinElmer STA6000 analyzer from 30 to 650 C. at a rate of 10 C. min.sup.1 under N.sub.2 flow.

[0070] The X-ray photoelectron spectroscopy (XPS) spectra were obtained using an ESCALAB-MKII spectrometer with an Al K X-ray source by using C is (284.5 eV) as the reference. The X-ray absorption spectroscopy was carried out in a transmission mode at the beamline X-ray absorption fine structure for catalysis (XAFCA) of Singapore Synchrotron Light Source operated at 700 MeV with the beam current of 200 mA. The data processing was conducted using the Athena and Artemis software packages. The solution after saturated KCl exchanged was analyzed by nuclear magnetic resonance spectroscopy (NMR 300 MHz, Bruker AVANCE III BBO Probe). The ratio of Cu to Co of HCuCo, Co.sub.0.1CuCo, Fe.sub.0.1CuCo, NiCuCo were confirmed by the inductively coupled plasma optical emission spectrometry (ICP-OES, PerkinElmer, Optima 8000).

Single Component Static Adsorption

[0071] For the porosity analysis, nitrogen adsorption-desorption experiments were executed at 77 K on an Autosorb iQ2 adsorptometer, Quantachrome Instrument. The adsorption isotherms for CO.sub.2, N.sub.2, etc. at 273 K and 298 K were also recorded on the same instrument. Prior to gas adsorption measurement, approximately 50 mg of the freshly-prepared samples were activated under high vacuum at 100 C. for 12 h.

Adsorption Breakthrough Experiments

[0072] The breakthrough experiments of C.sub.3H.sub.6/C.sub.2H.sub.4 were carried out in the Multi-constituent Adsorption Breakthrough equipment at 273 K. All experiments were conducted by using a column with 6 mm inner diameter and approximately 45 nm height. The weight of the packing sample was between 0.4 to 0.6 g. The column packed with the samples were firstly activated at 100 C. for 720 min, then purged with He flow (20 mL min.sup.1) at the target temperature. The mixed gas (50/50, v/v) flow were introduced at 5 mL min.sup.1. Outlet gas from the column was monitored on-line mass spectrometry (BSD-MASS) with a thermal conductivity detector (TCD).

[0073] The breakthrough experiments of CO.sub.2/CH.sub.4 were conducted using a lab-scale fix-bed reactor at 298 K. In a typical experiment, the powder was activated at 373 K for 24 h. Then 100 mg of material was packed into a quartz column (5.8 mm I.D.150 mm) with silane treated glass wool filling the void space. A helium flow (1 mL min.sup.1) was used to purge the adsorbent at 373 K for 5 h and then the system was cooled down to 298 K. The flow of helium was then turned off while the mixture of CO.sub.2 and CH.sub.4 (50/50, v/v) at a rate of 1 mL min.sup.1 was allowed to flow into the column. The effluent from the column was monitored using an-online mass spectrometer.

Example 2

Synthesis of Hexagonal Phase CuCo Prussian Blue Analog Materials (HCuCo)

[0074] Referring to FIG. 1, instead of the conventional approach to prepare cubic PBA (CCuCo) with or without vacancies, hexagonal phase copper-cobalt Prussian blue analog materials (referred to as HCuCo) were synthesized using a phase-engineering strategy and a simple co-precipitation method. FIG. 2 illustrated the synthesis process of the HCuCo, which required neither high-temperature treatment nor any other post-treatment.

[0075] For the synthesis of HCuCo, a facile co-precipitation was applied. 5 mL of deionized (DI) water contained 0.2 mmol of CuCl.sub.2.Math.2H.sub.2O and 0.2 mmol of sodium citrate was added into the mixed solution of 5 ml DI water and 25 ml DMF which dissolved 0.2 mmol of K.sub.3Co(CN).sub.6 and 0.2 g of PVP. Then, the above solution was continuously stirred for 48 h in the 30 C. water bath. After the reaction completed, the precipitate was collected by centrifugation and rinsed with DI water and ethanol for 3 times, respectively. Finally, the collected sample was dried at 80 C. for 12 h.

Synthesis of Cubic Phase CuCo PBA Cubes (CCuCo)

[0076] 15 ml of DI water dissolved 0.145 g Cu(NO.sub.3).sub.2 and 0.75 mmol of sodium citrate was added into 15 ml of DI water containing 0.133 g K.sub.3Co(CN).sub.6, and stirred for 12 h at ambient temperature. When the reaction finished, the precipitate was collected by centrifugation and rinsed with DI water and ethanol 3 times, respectively. Finally, the collected sample was dried at 80 C. in the oven for 12 h.

Example 3Characterization of the PBAs

[0077] Turning to FIG. 3A, the XRD pattern showed that the XRD of CCuCo was consistent with the traditional PBAs' pattern (Fm3m, fcc phase), whereas the XRD pattern of HCuCo was totally different from that of CCuCo. Both sharp and broad peaks were visible in the XRD pattern of HCuCo, indicating the possible presence of stacking disorders in its lattice structure. Therefore, confirming the crystalline structure of HCuCo via conventional methods was nearly impossible.

[0078] The emerging three-dimensional (3D) electron diffraction (ED) had been considered a powerful method for structure determination.sup.2-5. One of the specific methods of rotation electron diffraction (RED) had been utilized for solving initial structural models from a variety of functional crystalline materials.sup.2,6. In particular, the continuous RED (cRED) could collect hundreds of ED patterns in a short time (<5 min) and low electron dose rate.sup.7-8, so that the cRED not only solved the initial structural models but also refined certain crystalline materials.

[0079] To precisely confirm the structure of HCuCo, the cRED was utilized to solve the lattice structure of HCuCo. The hexagonal CuCo PBA unit cell parameters (a=12.1 , b=12.1 , c=12.7 , a=90.52, =89.70, and =119.53) was deduced by cRED. Referring to FIG. 3B, reflection conditions were obtained from the 2D slices cut from the 3D reciprocal lattice to be h-h01: 1=2n, which led to three possible space groups: P63 cm (No. 185), P-6c2 (No. 188), and P63/mcm (No. 193).

[0080] The cRED data was further processed and intensities were extracted using the X-ray Detector Software (XDS). Ab initio structure solution was performed using the highest space group suggested by SHELXT for the initial structure solution by direct methods implanted in SHELXT.sup.9. There were six Cu ions, four Co ions, and twenty-four cyanogen groups within one unit cell. Each Cu ion coordinated with four cyanogen groups displaying a plane quadrilateral configuration, while each Co ion connected with six cyanogen groups showing an octahedral configuration, which was different from the conventional cubic lattice. In this instance, octahedra and quadrilaterals were connected by alternatively sharing the cyanogen group. This created a 12-ring pore channel along the c-axis, considering only the metal ions.

Example 4Atomic Ambient for Elements in the HCuCo

[0081] XPS was performed and the results were shown in the FIGS. 3C-3D. As shown in FIG. 3D, the entire XPS spectrum of HCuCo was consistent with that of the traditional cubic phase CCuCo, indicating identical compositions of Cu, Co, C, and N. Specifically, for the Co element in both HCuCo and CCuCo, FIG. 3C showed similar XPS patterns without a satellite peak, corresponding to Co.sup.III in CoCN.sup.10-11. In addition, in HCuCo, there was a slight shift to lower energy for Co element compared to CCuCo. This difference may be attributed to variations in the number of neighboring atoms or differences in crystal structures. Cu.sup.I and Cu.sup.II both existed in the CCuCo and HCuCo. However, Cu.sup.I was clearly observed in HCuCo, with a Cu.sup.I:Cu.sup.II ratio of 1.00:1.50, in contrast to the ratio of 1:14.15 observed in CCuCo. This suggested that a large amount of Cu.sup.II had been reduced to Cu.sup.I. Besides, a similar redshift was also displayed in the HCuCo. Therefore, the unit cell composition of its framework with the negative charges should be [Cu.sup.+.sub.0.6Cu.sup.2+.sub.0.9Co.sup.3+.sub.1(CN).sub.6].sup.0.6. It was noteworthy that protonated dimethylamines (PDs) served as counter-cations, as confirmed by 1H Nuclear Magnetic Resonance (NMR) (FIG. 4A) and thermogravimetric analysis (TGA) results (FIG. 4B).

[0082] To further determine the positions of PDs, Rietveld refinement against PXRD data was employed. Derived from the initial structural model of CuCo-prism solved from cRED data, the final Rietveld refinement yielded a converged Rwp of 1.86% and a goodness of fit (GOF) of 2.2. This indicated that 2.4 PDs per unit cell were distributed within the 12-ring channels, balancing the negative charges from the framework.

[0083] As shown in FIGS. 5A-5B, the SEM images revealed the hexagonal prism morphology of the HCuCo. Turning to FIG. 5C, the TEM images of HCuCo also showed the hexagonal prism morphology and reveals the size of the prism was around 125 nm*400 nm. For comparison, the SEM (FIG. 5D) and TEM (FIG. 5E) images of the traditional cubic CuCo PBA displayed the cube morphology with a size of around 180 nm*180 nm.

[0084] Referring to FIG. 5F, the corresponding selected area electron diffraction (SAED) pattern along the [1-10] zone axis was displayed. This pattern was fitted to the hexagonal phase instead of the conventional face-centered cubic (fcc) phase of PBA. The high-resolution transmission electron microscopy (HRTEM) image in FIG. 5G was captured from the white square marked in FIG. 5C. It showed lattice fringes with a spacing of approximately 1.40 nm.

[0085] FIG. 5H showed the side view of the lattice of HCuCo of the [110]. By the high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) elemental mapping images (FIG. 5I), the equal distribution of the elements of Cu, Co, C, N were observable for the HCuCo. The similar chemical composition of Cu, Co, C, N of HCuCo and CCuCo were confirmed by the energy-dispersive X-ray spectroscopy (EDS), as shown in FIGS. 6A-6B.

Example 5Extended Synthesis

[0086] To expand the novel hexagonal phase CuCo PBA, Co, Fe, Ni, and Zn were doped into the synthesis (denote as Co.sub.0.1CuCo, Fe.sub.0.1CuCo, Fe.sub.0.2CuCo, Ni.sub.0.1CuCo, and Zn.sub.0.1CuCo

Synthesis of Hexagonal Phase Co.SUB.0.1.CuCo PBAs

[0087] 5 mL of DI water contained 0.2 mmol of CuCl.sub.2.Math.2H.sub.20, 0.02 mmol of CoC.sub.2.Math.6H.sub.2O and 0.2 mmol of sodium citrate was added into the mixed solution of 5 ml DI water and 25 ml DMF which dissolved 0.2 mmol of K.sub.3Co(CN).sub.6 and 0.2 g of PVP. Then, above solution was continuously stirred for 48 h in the 30 C. water bath. After the reaction completed, the precipitate was collected by centrifugation and rinsed with DI water and ethanol 3 times, respectively. Finally, the collected sample was dried at 80 C. in the oven for 12 h.

Synthesis of Hexagonal Phase Fe.SUB.0.1.CuCo PBAs

[0088] 5 mL of DI water contained 0.2 mmol of CuCl.sub.2.Math.2H.sub.20, 0.02 mmol of FeCl.sub.3.Math.6H.sub.2O and 0.2 mmol of sodium citrate was added into the mixed solution of 5 ml DI water and 25 ml DMF which dissolved 0.2 mmol of K.sub.3Co(CN).sub.6 and 0.2 g of PVP. Then, above solution was continuously stirred for 48 h in the 30 C. water bath. After the reaction completed, the precipitate was collected by centrifugation and rinsed with DI water and ethanol 3 times, respectively. Finally, the collected sample was dried at 80 C. in the oven for 12 h.

Synthesis of Hexagonal Phase Fe.SUB.0.2.CuCo PBAs

[0089] 5 mL of DI water contained 0.2 mmol of CuCl.sub.2.Math.2H.sub.20, 0.04 mmol of FeCl.sub.3.Math.6H.sub.2O and 0.2 mmol of sodium citrate was added into the mixed solution of 5 ml DI water and 25 ml DMF which dissolved 0.2 mmol of K.sub.3Co(CN).sub.6 and 0.2 g of PVP. Then, above solution was continuously stirred for 48 h in the 30 C. water bath. After the reaction completed, the precipitate was collected by centrifugation and rinsed with DI water and ethanol 3 times, respectively. Finally, the collected sample was dried at 80 C. in the oven for 12 h.

Synthesis of Hexagonal Phase Ni.SUB.0.1.CuCo PBAs

[0090] 5 mL of DI water contained 0.2 mmol of CuCl.sub.2.Math.2H.sub.20, 0.04 mmol of NiCl.sub.2.Math.6H.sub.2O and 0.2 mmol of sodium citrate was added into the mixed solution of 5 ml DI water and 25 ml DMF which dissolved 0.2 mmol of K.sub.3Co(CN).sub.6 and 0.2 g of PVP. Then, above solution was continuously stirred for 48 h in the 30 C. water bath. After the reaction completed, the precipitate was collected by centrifugation and rinsed with DI water and ethanol 3 times, respectively. Finally, the collected sample was dried at 80 C. in the oven for 12 h.

Synthesis of Hexagonal Phase Zn.SUB.0.1.CuCo PBAs

[0091] 5 mL of DI water contained 0.2 mmol of CuCl.sub.2.Math.2H.sub.20, 0.02 mmol of ZnCl.sub.2, and 0.2 mmol of sodium citrate were added into the mixed solution of 5 ml DI water and 25 ml DMF which dissolved 0.2 mmol of K.sub.3Co(CN).sub.6 and 0.2 g of PVP. Then, above solution was continuously stirred for 48 h in the 30 C. water bath. After the reaction completed, the precipitate was collected by centrifugation and rinsed with DI water and ethanol 3 times, respectively. Finally, the collected sample was dried at 80 C. in the oven for 12 h.

[0092] As shown in FIGS. 7A-7D, after doping different transition metal elements with other synthesis conditions constantly, the morphologies of the hexagonal phase PBA transformed from the hexagonal prism to sheet and column. A series of high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) images and corresponding elemental mappings indicated that dopant atoms were successfully introduced into the CuCo PBA. This suggested that dopant atoms could significantly impact the morphology. Although the morphology changed dramatically, their XRD patterns indicated that the doped materials still retained the hexagonal phase.

[0093] To further investigate the effect of dopant atoms, the XPS test for Cu element of these 5 doped materials was performed (FIG. 8). The XPS spectrums revealed that the ratio of Cu.sup.I:Cu.sup.II were different, which the ratio of Cu.sup.I in Fe.sub.0.1CuCo, Fe.sub.0.2CUCO, Ni.sub.0.1CuCo, and Zn.sub.0.1CuCo were increased a lot compared with HCuCo. While the ratio of Cu.sup.I was declining in Co-.sub.0.1CuCo. This indicated that the amount of unsaturated Cu atoms could be modulated by introducing different dopant metallic atoms.

[0094] In addition, it was found that the dopant atom could impact the amount of unsaturated copper in the hexagonal phase CuCo PBA. For example, Ni, Fe, and Zn increased the content of Cu.sup.I, while doping with Co reduced the amount of Cu.sup.I. Thus, based on the XPS results and inductively coupled plasma (ICP) results of the ratio of Cu:Co (Table 4), it was concluded that the formulas of the dopant CuCo PBAs should be [Co.sup.2+.sub.0.16Cu.sup.+.sub.0.41Cu.sup.2+.sub.0.93Co.sup.3+.sub.0.84(CN).sub.6].sup.0.89, [F.sup.3+.sub.0.02Cu.sup.+.sub.1.32Cu.sup.2+.sub.0.44+Co.sup.3+.sub.1(CN).sub.6].sup.0.74, [Fe.sup.3+.sub.0.03Cu.sup.+.sub.1.25Cu.sup.2+.sub.0.42Co.sup.3+.sub.1(CN).sub.6].sup.0.82, and [Ni.sup.2+.sub.0.06Cu.sup.+.sub.1.12Cu.sup.2+.sub.0.48Co.sup.3+.sub.1(CN).sub.6].sup.0.8, [Zn.sup.2+.sub.0.21Cu.sup.+.sub.1.09Cu.sup.2+.sub.0.38Co.sup.3+.sub.1(CN).sub.6].sup.0.73 respectively, for Co.sub.0.1CuCo, Fe.sub.0.1CuCo, Fe.sub.0.2CuCo, Ni.sub.0.1CuCo, and Zn.sub.0.1CuCo.

[0095] Table 4Atom Ratio of Cu:Co which based on the ICP result for HCuCo, Co.sub.0.1CuCo, Fe.sub.0.1CuCo, Fe.sub.0.2CuCo, Ni.sub.0.1CuCo, and Zn.sub.0.1CuCo.

TABLE-US-00001 Material Cu Co CCuCo 1.40 1 HCuCo 1.50 1 Co.sub.0.1CuCo 1.34 1 Ni.sub.0.1CuCo 1.57 1 Fe.sub.0.1CuCo 1.76 1 Fe.sub.0.2CuCo 1.67 1 Zn.sub.0.1CuCo 1.47 1

Example 6Gas Uptake and Separation Performance

[0096] To confirm the permanent porosity after solvent removal, Brunauer-Emmett-Teller (BET) nitrogen gas adsorption experiments were conducted at 77 K. Brunauer-Emmett-Teller (BET) nitrogen gas adsorption experiments are a common experimental method used for surface area measurement and pore structure analysis. This technique involves the adsorption of nitrogen gas onto the surface of a material at various pressures to determine its specific surface area and pore structure. By measuring the amount of nitrogen adsorbed on the material surface as a function of adsorption pressure, parameters such as specific surface area, pore volume, and pore size distribution can be calculated, providing valuable insights into the material's pore structure characteristics.

[0097] Before the BET test, HCuCo and CCuCo were treated at 100 C. in vacuum, and the XRD patterns before and after treatment were collected. Referring to FIG. 9, the XRD patterns of CCuCo before and after treatment were nearly identical. However, a peak at 17.6 disappeared for HCuCo after the drying treatment. This should be due to the gas degassing. Additionally, it was observed that the color of HCuCo was purple when it was removed from the vacuum, but turned blue upon exposure to air, indicating the stable structure of HCuCo.

[0098] FIG. 10A of BET showed the surface area calculated via DFT calculation of 1273.244 m.sup.2 g.sup.1 of HCuCo, in contrast to the surface area of 443.416 m.sup.2 g.sup.1. Compared to other conventional PBAs, the surface area of HCuCo was significantly higher, exceeding 900 m.sup.2 g.sup.1, whereas the reported surface area of other PBAs was lower than 900 m.sup.2 g.sup.1. Additionally, FIG. 10B illustrated that HCuCo had three types of pores, with half pore widths of 2.74, 4.30, and 6.16 , contributing to a total pore volume of 0.800 cm.sup.3 g.sup.1. This contrasted with CCuCo, which had only one type of pores with a half pore width and pore volume of 0.217 cm.sup.3 g.sup.1.

[0099] In the following, the sorption isotherms of single-component gases (CO.sub.2, CH.sub.4, C.sub.2H.sub.2, C.sub.2H.sub.4, C.sub.2H, C.sub.3H.sub.6, and C.sub.3H.sub.8) of HCuCo and CCuCo PBAs were carried out at 273 to 298 K (FIG. 10C, and Table 1).

TABLE-US-00002 TABLE 1 Gas sorption performance of HCuCo, CCuCo, Fe.sub.0.1CuCo, Fe.sub.0.2CuCo and Co.sub.0.1CuCo. surface CO.sub.2 CH.sub.4 C.sub.2H.sub.2 C.sub.2H.sub.4 C.sub.2H.sub.6 C.sub.3H.sub.6 C.sub.3H.sub.8 area adsorption adsorption adsorption adsorption adsorption adsorption adsorption Material (m.sup.2 g.sup.1) (cm.sup.3 g.sup.1) (cm.sup.3 g.sup.1) (cm.sup.3 g.sup.1) (cm.sup.3 g.sup.1) (cm.sup.3 g.sup.1) (cm.sup.3 g.sup.1) (cm.sup.3 g.sup.1) HCuCo 1273 136.7 28.0 70.6 76.0 116.9 114.9 107.3 (273K) (273K) (273K) (273K) (273K) (273K) (273K) 93.7 12.5 56.3 59.6 90.9 90.1 86.9 (298K) (298K) (298K) (298K) (298K) (298K) (298K) CCuCo 443 89.6 16.7 32.3 36.9 44.5 64.2 43.8 (273K) (273K) (273K) (273K) (273K) (273K) (273K) 69.6 7.6 26.7 30.8 36.1 50.6 35.5 (298K) (298K) (298K) (298K) (298K) (298K) (298K) Fe.sub.0.1CuCo 969 107.4 23.3 139.1 114.0 91.7 125.9 99.1 (273K) (273K) (273K) (273K) (273K) (273K) (273K) 68.6 11.5 101.6 83.1 77.6 96.0 87.7 (298K) (298K) (298K) (298K) (298K) (298K) (298K) Fe.sub.0.2CuCo 799 95.8 20.3 110.3 102.4 82.9 105.5 91.7 (273K) (273K) (273K) (273K) (273K) (273K) (273K) 62.0 10.1 83.7 66.0 70.7 74.9 80.0 (298K) (298K) (298K) (298K) (298K) (298K) (298K) Co.sub.0.1CuCo 937 91.0 21.0 118.3 106.9 79.4 114.4 86.8 (273K) (273K) (273K) (273K) (273K) (273K) (273K) 66.4 10.6 90.1 75.0 66.6 81.9 74.0 (298K) (298K) (298K) (298K) (298K) (298K) (298K)

[0100] In particular, HCuCo exhibited a gravimetric C.sub.2 uptake of 136.41 cm.sup.3 g.sup.1 (6.09 mmol g.sup.1) at 273 K, 1 bar, indicating that 8.2 CO.sub.2 molecules were captured by 1HCuCo. For 298 K and 1 bar, the CO.sub.2 uptake of HCuCo was 93.65 cm.sup.3g.sup.1 (4.18 mmol g.sup.1). Both of these CO.sub.2 uptakes exceeded the values of 89.57 and 69.87 cm.sup.3 g.sup.1 (4.00 and 3.12 mmol g.sup.1) for CCuCo at 273 K and 298 K, respectively, at 1 bar.

[0101] For CH.sub.4, C.sub.2H.sub.2, C.sub.2H.sub.4, C.sub.2H.sub.6, C.sub.3H.sub.6, and C.sub.3H.sub.8, the HCuCo also showed better uptake capabilities, more than 1.5 times that of CCuCo under the same conditions, which indicated the hexagonal phase CuCo PBA processes much better gas uptake capability than the conventional cubic phase of CuCo PBA. Table 2 also demonstrated that the CO.sub.2 adsorption capacity of HCuCo was among the highest compared to previously reported materials.

TABLE-US-00003 TABLE 2 Selected examples for CO.sub.2 storage. CO.sub.2 adsorption Surface area.sup.a Temperature capacity.sup.b Material (m.sup.2/g) (K) (mmol/g) Noted CO.sub.2 adsorption performance of PBA materials HCuCo 1273 273 6.1 This 298 4.2 work CCuCo 443 273 4.0 298 3.1 Fe.sub.0.1CuCo 960 273 4.8 Fe.sub.0.2CuCo 799 273 4.3 Co.sub.0.1CuCo 937 273 4.1 K.sub.2x/3Cu.sup.II [Fe.sup.II.sub.xFe.sup.III.sub.1x 504 273 4.5 Prior art (CN).sub.6].sub.2/3nH.sub.2O (x = 0) K.sub.2x/3Cu.sup.II [Fe.sup.II.sub.xFe.sup.III.sub.1x 370 273 3.0 (CN).sub.6].sub.2/3nH.sub.2O (x = 1) K.sub.0.24+yNi.sub.2.88[Fe.sup.II.sub.yFe.sup.III.sub.1y(CN).sub.6].sub.2nH.sub.2O 110 273 3.0 CO.sub.2 adsorption performance of silicate materials Fe-MOR(0.25) 282 273 5.7 Prior art NaTEA-ZSM-25 298 3.5 Na-Rho 298 4.5 SGU-29 457 298 3.5 CO.sub.2 adsorption performance of COF materials JUC-505 1584 273 5.3 Prior art 2D sql COF 3478 298 1.76 CoTAPP-PATA-COF 944 273 2.1 RC-COF-1 1712 273 6.6 CO.sub.2 adsorption performance of MOF materials SIFSIX-2-Cu-i 735 298 5.4 Prior art SIFSIX-3-Zn 250 298 2.5 Mg2V-DHBDC 1475 (2117.sup.c) 273 10.4 Mn.sup.IIMn.sup.III(OH)Cl.sub.2(bbta) 1286.sup.c 298 7.1 FJI-14H 904 (1004.sup.c) 298 12.5 mmen-Mg.sub.2(dobpdc) 3326 298 4.1 CALF-20 528.sup.c 293 4.1 (1.2 bar) [(Y.sub.0.95Eu.sub.0.05)(H.sub.3pptd)]xSolvent 566 195 7.3 (0.3 bar) [K.sub.3(Y.sub.0.95Eu.sub.0.05)(pptd)]zSolvent 498 195 6.7 (0.3 bar) Im-UiO-PL 298 5.9 (9 bar) ALF 588 273 2.7 Qc-5-Cu-sql- 222 293 2.2 CG-3 1470 273 7.9 CG-9 1532 273 8.3 PN@MOF-5 1200 273 3.5 Tetramethylammonium@bio-MOF-1 1460 273 4.5 LIFM-33 1589 273 3.6 [Mn(bdc)(dpe)] 535 195 5.0 {[Zn.sub.2(BME-bdc).sub.2- 195 7.0 (bipy)].sub.n(DMF).sub.2.3(EtOH).sub.0.4} SHF-61-CHCl.sub.3 544.sup.c 298 6.3 (19.5 bar) CPM-5 580 (733.sup.c) 273 3.6 CPM-6 596 (931) 273 4.8 (choline).sub.3[In.sub.3(btc).sub.4]2 DMF 508 (712.sup.c) 273 3.2 CPM-33a 966 (1257.sup.c) 273 6.1 CPM-33b 808 (1119.sup.c) 273 7.8 NOTT-202a 2220 195 20.0 Ni4PyC 945 298 8.2 (10 bar) [Zn(2)].sub.n (3) 802 298 2.1 CPF-6 599 (883.sup.c) 273 4.4 MAF-23 622.sup.c 273 3.3 MAF-25 511.sup.c 195 5.2 Cu-TDPAT 1938 (2608.sup.c) 298 5.9 IRMOF-74-III-CH.sub.2NH.sub.2 2310 298 3.3 IRMOF-74-III-(CH.sub.2NH.sub.2).sub.2 298 3.0 CAU-1 1268 273 7.2 PCN-88 3308 (3845.sup.c) 273 7.1 Cu-BTTri (1) 1770 (1900.sup.c) 298 3.2 SNU-5 2850.sup.c 273 1.7 .sup.aUnless otherwise stated, the surface area is calculated by the Brunauer-Emmett-Teller (BET) methods. .sup.bUnless otherwise stated, the CO.sub.2 adsorption amount measured at 1 bar. .sup.cThe surface area is calculated by the Langmuir method.

[0102] What is more, experimental breakthrough experiments were conducted for C.sub.3H.sub.6/C.sub.2H.sub.4 (50/50, v/v) at 273 K. Referring to FIG. 11, the C.sub.2H.sub.4 breakthrough occurred at 439 s/g for HCuCo PBAs, while almost the same time for CCuCo PBAs at 412 s/g. However, the retention time of C.sub.3H.sub.6 in the packed column for HCuCo was 779 s/g, which was longer than that of CCuCo, which was 670 s/g. The separation coefficient of C.sub.3H.sub.6 to C.sub.2H.sub.4 for HCuCo was 6.82, which was twice that of CCuCo, which was 3.35.

[0103] Referring to FIG. 12, unlike CCuCo, which showed no separating behavior for CO.sub.2/CH.sub.4, HCuCo exhibited potential CO.sub.2/CH.sub.4 separation behavior, representing a significant breakthrough. These results suggested that phase engineering offered a new and promising strategy for gas capture and separation.

[0104] To further explore the gas capture performance of the dopant CuCo PBA, serials of BET and single gas uptake measurements were performed (Table 5 and FIGS. 13A-13H).

TABLE-US-00004 TABLE 5 Surface area of PBAs. Materials Surface area (m.sup.2 g.sup.1) Note HCuCo 1273 This work CCuCo 443 Fe.sub.0.1CuCo 960 Fe.sub.0.2CuCo 799 Co.sub.0.1CuCo 937 CoHCF 547 Prior art CoHCC 848 Mn.sub.3[Co(CN).sub.6].sub.2 870 Fe.sub.3[Co(CN).sub.6].sub.2 770 Co.sub.3[Co(CN).sub.6].sub.2 800 Ni.sub.3[Co(CN).sub.6].sub.2 560 Cu.sub.3[Co(CN).sub.6].sub.2 730 Zn.sub.3[Co(CN).sub.6].sub.2 720 Ga[Co(CN).sub.6] 570 Fe.sub.4[Fe(CN).sub.6].sub.3 550 Cu.sub.3[Co(CN).sub.6].sub.2 750 Co.sub.2[Fe(CN).sub.6] 370 Ni.sub.2[Fe(CN).sub.6] 460 Cu.sub.2[Fe(CN).sub.6] 730 Co.sub.3[Co(CN).sub.5].sub.2 730 Cu.sup.III.sub.3[Co.sup.II(CN).sub.6].sub.2 793 Mn.sup.III.sub.3[Co.sup.II(CN).sub.6].sub.2 783 Ni.sup.III.sub.3[Co.sup.II(CN).sub.6].sub.2 529 Co.sup.III.sub.3[Co.sup.II(CN).sub.6].sub.2 712 Zn.sup.III.sub.3[Co.sup.II(CN).sub.6].sub.2 700 K.sub.1.04+yNi.sub.2.48[Fe.sup.II.sub.yFe.sup.III.sub.1y(CN).sub.6].sub.2 nH.sub.2O 72 K.sub.0.24+yNi.sub.2.88[Fe.sup.II.sub.yFe.sup.III.sub.1y(CN).sub.6].sub.2 nH.sub.2O 110 K.sub.2x/3Cu.sup.II [Fe.sup.II.sub.xFe.sup.III.sub.1x (CN).sub.6].sub.2/3nH.sub.2O 504 (x = 0) K.sub.2x/3Cu.sup.II [Fe.sup.II.sub.xFe.sup.III.sub.1x (CN).sub.6].sub.2/3nH.sub.2O 370 (x = 1) [Co.sub.3Fe.sub.2] 448 [Ni.sub.3Fe.sub.2] 541 [Cu.sub.3Fe.sub.2] 422 [Mn.sub.3Fe.sub.2] 704 [Fe.sub.3Fe.sub.2] 677 [Co.sub.3Co.sub.2] 678 [Ni.sub.3Co.sub.2] 670 [Cu.sub.3Co.sub.2] 689 [Mn.sub.3Co.sub.2] 869 [Fe.sub.3Co.sub.2] 779 Li.sub.2Zn.sub.3[Fe(CN).sub.6].sub.22H.sub.2O 250 Na.sub.2Zn.sub.3[Fe(CN).sub.6].sub.2 570 K.sub.2Zn.sub.3[Fe(CN).sub.6].sub.2 470 Rb.sub.2Zn.sub.3[Fe(CN).sub.6].sub.2 430 Zn.sub.3[Co(CN).sub.6].sub.2 720

[0105] Compared to Co.sub.0.1CuCo, Fe.sub.0.1CuCo exhibited a higher specific surface area and better gas capture performance. This suggested that unsaturated active atoms enhanced the storage of small molecular gases. Furthermore, the results showed that doping CuCo PBA significantly increased gas uptake performance, such as for C.sub.2H.sub.4 and C.sub.2H.sub.6. However, excessively high doping rates led to lower specific surface area and gas uptake performance.

Example 7Mechanism

[0106] To study the reason for enhancing performance of HCuCo, the XAFS measurements were performed to evaluate the local electronic and geometric structures of the metal elements in the as-prepared HCuCo. The K-edge X-ray absorption near edge structure (XANES) for the Co element of HCuCo, CCuCo, and K.sub.3Co(CN).sub.6 was shown in FIG. 14A. The similar curves of the XANES pattern for Co further confirmed that HCuCo belongs to the PBA family. Besides, the well-overlapped pre-edge XANES pattern of Co displayed that the Co element in the HCuCo, CCuCo, and K.sub.3Co(CN).sub.6 had the same valence and circumstances of CoCN.

[0107] In the corresponding Fourier transform X-ray absorption fine structure (FT-EXAFS) of K-edge for Co (FIG. 14B), the peaks located at 1.47, 2.55, and 4.45 in R space should be denoted as attributed to CoC, CoCN, and CoCNCu scattering respectively.

[0108] In addition, based on the intensity of wavelet transforms (WT) of EXAFS (FIG. 14C) for CoC and CoCN, it is suggested that HCuCo, CCuCo and K.sub.3Co(CN).sub.6 have the same coordination number for CoC and CoCN. However, the intensity of CoCNCu of HCuCo in WT and FT-EXAFS was obviously lower than the CCoCu that in CCuCo for Co element, meaning the lower coordination number of CoCNCu in HCuCo.

[0109] Besides, the Cu K-edge XANES of HCuCo, CCuCo, Cu.sub.2O, CuO, and CuPc were tested. The highly similar absorption energies and the white-line peak profiles of HCuCo and CCuCo in the XANES proved the PBAs family's feature once again, while they are quite different from the features of CuPc, CuO and Cu.sub.2O references due to the diverse atom environments of CuNC for PBAs. The pre-edge absorption energy of HCuCo slightly shifted to lower energy, indicating a lower valence of Cu in HCuCo. Besides, based on the pre-edge curve of CuPc, the slightly higher pre-edge peak at around 8987 eV of HCuCo suggested more plane quadrilateral configuration than CCuCo for Cu element.

[0110] In the FT-EXAFS of Cu, the peaks located at 1.56 and 2.60 Ain R space should be assigned to CuN and CuNC scattering, which was similar to CuPc. The intensities of CuN for HCuCo and CCuCo were the same, while the intensity of CuNC for HCuCo was slightly lower than CCuCo, that was because of more planar configuration for Cu atoms. For peaks at 4.60 , it should be denoted as the CuNCCo, and the CuNCCo bonds also showed a similar situation of obviously lower intensity in HCuCo, which consisted of the FT-EXAFS of Co. These features were also confirmed by wavelet transforms (FIG. 14). Then, after performing fitting and calculating via FT-EXAFS of Co and Cu (FIGS. 15A-15D), detailed coordination numbers of HCuCo and CCuCo were listed in Table 3.

TABLE-US-00005 TABLE 3 EXAFS fitting results. Sample Path CN .sup.2 E.sub.0 R R-factor CuCo CuN 4.3(0.5) 0.0036(0.0012) 4.84(1.14) 1.98(0.01) 0.019 Prism CuC 4.3(0.5) 0.0038(0.0013) 4.84(1.14) 3.15(0.01) CoC 6.3(0.5) 0.0023(0.0008) 0.04(0.88) 1.89(0.01) CoN 6.3(0.5) 0.0013(0.0005) 0.04(0.88) 3.06(0.01) CuCo CuN 4.8(0.5) 0.0048(0.0013) 4.60(1.11) 2.00(0.01) 0.019 Cube CuC 4.8(0.5) 0.0039(0.0015) 4.60(1.11) 3.17(0.01) CoC 6.3(0.5) 0.0024(0.0007) 0.00(0.87) 1.89(0.01) CoN 6.3(0.5) 0.0014(0.0006) 0.00(0.87) 3.06(0.01)

[0111] The results indicated that the coordination numbers of CoC and CoCN were the same for HCuCo and CCuCo. However, the coordination numbers of CuN and CuNC in HCuCo were lower than those in CCuCo due to the presence of some unsaturated Cu forming a planar configuration, which was consistent with the above analysis.

[0112] The presence of opened metal sites could have contributed to both uptake capacity and separation selectivity. Therefore, it was considered that the superior gas uptake and separation performance not only arose from the higher specific surface area but also from the abundance of planar configurations of CuNC, which provided opened and unsaturated Cu atoms with low valence to coordinate with gas molecules. This beneficial effect was attributed to the novel hexagonal phase of HCuCo.

INDUSTRIAL APPLICABILITY

[0113] The hexagonal phase HCuCo PBAs and their doping derivatives find extensive application in various fields due to their unique properties, such as gas storage and separation, electrochemical biosensors, photothermal therapy, catalysis, nanozymes, drug delivery systems, removal of radioactive ions, energy storage devices and water desalination technologies.

Definitions

[0114] Throughout this specification, unless the context requires otherwise, the word comprise or variations such as comprises or comprising, will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers. It is also noted that in this disclosure and particularly in the claims and/or paragraphs, terms such as comprises, comprised, comprising and the like can have the meaning attributed to it in U.S. patent law; e.g., they allow for elements not explicitly recited, but exclude elements that are found in the prior art or that affect a basic or novel characteristic of the present invention.

[0115] Furthermore, throughout the specification and claims, unless the context requires otherwise, the word include or variations such as includes or including, will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.

[0116] As used herein and not otherwise defined, the terms substantially, substantial, approximately and about are used to describe and account for small variations. When used in conjunction with an event or circumstance, the terms can encompass instances in which the event or circumstance occurs precisely as well as instances in which the event or circumstance occurs to a close approximation. For example, when used in conjunction with a numerical value, the terms can encompass a range of variation of less than or equal to 10% of that numerical value, such as less than or equal to 5%, less than or equal to 4%, less than or equal to 3%, less than or equal to 2%, less than or equal to 1%, less than or equal to 0.5%, less than or equal to 0.1%, or less than or equal to 0.05%.

[0117] References in the specification to one embodiment, an embodiment, an example embodiment, etc., indicate that the embodiment described can include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.

[0118] In the methods of preparation described herein, the steps can be carried out in any order without departing from the principles of the invention, except when a temporal or operational sequence is explicitly recited. Recitation in a claim to the effect that first a step is performed, and then several other steps are subsequently performed, shall be taken to mean that the first step is performed before any of the other steps, but the other steps can be performed in any suitable sequence, unless a sequence is further recited within the other steps. For example, claim elements that recite Step A, Step B, Step C, Step D, and Step E shall be construed to mean step A is carried out first, step E is carried out last, and steps B, C, and D can be carried out in any sequence between steps A and E, and that the sequence still falls within the literal scope of the claimed process. A given step or sub-set of steps can also be repeated. Furthermore, specified steps can be carried out concurrently unless explicit claim language recites that they be carried out separately.

[0119] Cu.sup.I and Cu.sup.II refer to different oxidation states of copper. Cu.sup.I represents the +1 oxidation state of copper (copper(I) or cuprous), while Cu.sup.II represents the +2 oxidation state (copper(II) or cupric).

[0120] Other definitions for selected terms used herein may be found within the detailed description of the present invention and apply throughout. Unless otherwise defined, all other technical terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which the present invention belongs.

REFERENCE

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