A TITANIUM-ORGANIC FRAMEWORK MATERIAL

Abstract

This patent mentioned the synthesis of new metal-organic framework based on hexameric titanium-oxo cluster. The novel material, termed MOF-902, was successfully synthesized and its crystal structure uncovered the 2-Dimensional (2D) layer structure generated by the link of trigonal prism Ti.sub.6O.sub.6(OMe)(COO).sub.6 clusters and imine linear linking units. The permanent porosity of MOF-902 is 400 m.sup.2 g.sup.1. The band gap energy of this material was found to be 2.5 eV which is suitable to catalyze the polymerization reaction of methacrylate monomers under visible irradiation.

Claims

1. A metal organic framework material, MOF-902, possessing 2D layer structure comprises Ti-oxo clusters and imine linking units; wherein every titanium atom links directly to a methoxide group (OCH.sub.3); and wherein the Ti-oxo clusters connected together through the imine linking units containing (HCN) linkage.

2. The metal organic framework material according to claim 1 further contains staggered layers which is infinite two-dimensional structure.

3. The metal organic framework material according to claim 1 further contains staggered layers, wherein the distance between two layers of the material is about 3.9(7) , having tolerance range of 0.7; and wherein a second layer of the material moving a certain distance leading to place the Ti-oxo clusters in the center of triangular pores of the first layer providing a hexagonal pore size about 16.1(2) with a tolerance range of 0.2.

4. The metal organic framework material according to claim 1, wherein the bonding distribution in Ti-oxo cluster of the material is TiOTiOTiO.

5. The metal organic framework material according to claim 4, wherein the TiO linkage is a covalent bond; and wherein the distance of the TiO linkage is approximately 1.87(7) with a tolerance range of 0.07.

6. The metal organic framework material according to claim 1, wherein the Ti-oxo clusters bind together via an imine linking unit which possesses imine functionality (HCN), and wherein the length of the organic linker is about 24.1(6) with a tolerance range of 0.6.

7. The metal organic framework material according to claim 1 having a formula of Ti.sub.6O.sub.24C.sub.90H.sub.72N.sub.6 (Ti: 15.0%, C: 57.0%, H: 4.0%, N; 4.0%).

8. The metal organic framework material according to claim 1 wherein the linking units comprise 4,4-biphenyldicarboxaldehyde.

9. The metal organic framework material according to claim 6 wherein the linking units comprise 4,4-biphenyldicarboxaldehyde.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] FIG. 1: The synthetic scheme of MOF-902

[0009] FIG. 2: The hexameric Ti-oxo cluster and imine linking unit in MOF-902 structure

DETAILED DESCRIPTION

[0010] Crystal structure of MOF-902 is determined by powder X-ray diffraction (CuK, =1.5459 ) and model simulation followed by refinement. The details of crystal structure described below are based on the single crystal structural model. Metal-organic framework-902 material (MOF 902) contains staggered layers which is infinite two-dimensional structure. The distance between the two layers is about 3.9(7) (tolerance error 0.7), the pore size is about 16.1(2) (tolerance range 0.2). The Ti-oxo metal clusters are arranged by alternately arrangement of titanium and oxygen to form a hexagonal prism. The bonding distribution in Ti-oxo cluster was found to be TiOTiOTiO. The distance of TiO bonding was approximately found to be 1.87(7) (an error tolerance of 0.07). Ti-oxo clusters bind together via an imine linking units which possess imine functionality (HCN) and the length of the organic linker is about 24.1(6) (error range 0.6). For meeting charge balance (to preserve tetravalence), each titanium atom links directly to an additional group of methoxides (OCH.sub.3). MOF-902 is capable of receiving energy from visible light irradiation and catalyzes for the polymerization reaction. The band-gap energy of MOF-902 was found to be 2.5 eV which is benefit to promote the synthesis of polymers from monomers such as methylmethacrylate (MMA), benzylmethacrylate (BMA), or Styrene (St). Under MOF-902 photocatalyst, the resulting polymers exhibited its uniform as proven by high molecular weight and low dispersion index (PDI).

[0011] Synthesis of MOF-902

[0012] MOF-902 was synthesized by solvothermal method. In general, 4-aminobenzoic acid, titanium(IV) isopropoxide, and 4,4-biphenyldicarboxaldehyde were mixed together under methanoic solution. The mixture was then transferred to the teflon container of Autoclave reactor and place in the isothermal oven which the temperature is set up at 140 C. for 3 days. The reaction was cooled down to room temperature and the yellow crystalline powder was collected by filtration.

[0013] MOF-902 absorbs the visible light with a broad range of optical absorption from 340 nm to 640 nm, in which the maximum absorption located at 390 nm. The band-gap energy of MOF-902 was calculated based on UV-vis diffuse reflectance spectroscopy corresponding to 2.5 eV. MOF-902 exhibits thermal stability at 200 C. The internal surface area of MOF-902 based on BET method is 400 m.sup.2 g.sup.1. MOF-902's density was found to be 0.95 g cm.sup.3. The elemental analysis reveals the formula of MOF-902 is Ti.sub.6O.sub.24C.sub.90H.sub.72N.sub.6(Ti: 15.0%, C: 57.0%, H: 4.0%, N; 4.0%/).

[0014] Polymers Preparation by MOF-902 Catalyst

[0015] Step 1: Charge the monomer (methylmethacrylat (MMA), benzylmethacrylat (BMA), or Styren (St)) into the vial which contains MOF-902 catalyst.

[0016] Step 2: The organic solvent (N,N-Dimethylformamide (DMF), 1,4-dioxane, or tetrahydrofuran (THF)) was then added to the reaction mixture. The vial was sealed by septum and parafilm to prevent the reaction from the air.

[0017] Step 3: The reaction mixture was frozen under liquid nitrogen bath and evacuated 3 times under reduced pressure by a Schlenk line system. Ethyl -bromophenylacetate (co-initiator) was then introduced to the reaction by a micro injector.

[0018] Step 4: The reaction mixture was stirred at room temperature 30 minutes before irradiated by a compact fluorescent light bulb 4U, 55W for 18 h. Polymer product was precipitated by methanol. The product was washed 3 times with methanol. MOF-902 catalyst was collected by centrifugation and immersed in DMF and dichloromethane before regeneration.

EXAMPLES OF THE PRESENT INVENTION

Example 1: Prepare 100 mg MOF-902

[0019] 4,4-Biphenyldicarboxaldehyde (147.2 mg, 0.701 mmol) was dispersed in 6 mL methanol and sonicated for 2 minutes. This dispersion was then transferred to 6 mL methanoic solution dissolving 4-aminobenzoic acid (192 mg, 1.401 mmol) and titanium(IV)isopropoxide (104 L, 0.352 mmol). The mixture was subsequently introduced to a teflon container of autoclave reactor and heated up to 140 C. for 3 days. The yellow crystalline powder of MOF-902 was collected and washed with N,N-dimethylacetamide (DMA) for 2 days with 4 times of replenishment solvent per day. MOF-902 was then immersed in dichloromethane for 3 days with 3 times of replenishment solvent per day. Activated MOF-902 was obtained after evacuation at low pressure and 130 C. for 24 hours.

Example 2: Prepare Polymethylmethacrylate (polyMMA)

[0020] The photocatalytic activity of MOF-902 was studied as follow: an activated MOF-902 (6.6 mg, 0.0038 mmol based on MOF-902 molecule mass) was loaded into a 8 mL glass vial. The mixture of methylmethacrylate (MMA) (602 L, 0.00570 mol) and 2.1 mL of DMF (0.0271 mol) was then introduced to the vial containing MOF-902 catalyst. The vial was sealed with a rubber septum and evacuated 3 times under reduced pressure by a Schlenk line system. Next, 4.5 L of ethyl -bromophenylacetate (0.024 mmol) was then introduced to the vial by a micro injector. The reaction solution was stirred for 30 min before irradiating 18 h with a compact fluorescent light bulb (4U, 55W) with speed at 1000 rpm. After 18 hours, the reaction vial was wrapped with an aluminum foil and allowed to stand for 1 hour. The catalyst was isolated by centrifugation and washed with dichloromethane several times before immersing to methanol 5 hours. MOF-902 was subsequently regenerated under vacuum medium (1 mTorr). The polyMMA product was crystallized in 80 mL methanol. The product was washed with methanol several times and evacuated at room temperature for 2 hours. The yield of polyMMA product was found to be in the rage from 50% to 84% depends on the nanoparticle size of MOF-902.

[0021] Uses of Invention (MOF-902)

[0022] MOF-902 as described above may be used as photocatalyst for organic synthesis of polymerization reactions. The quality of polymers is higher than using existing commercial catalysts such as P25-TiO.sub.2 or other related MOF catalysts (MIL-125, MIL-125-NH.sub.2, UiO-66 type). The quality of the polymers can be improved and the cost of product preparation can be reduced due to the reusable nature of MOF-902 catalyst which can be recycled at least 5 times without reducing the activity. In addition, this material possesses centers of active site which catalyze the polymerization reaction based on the free radical mechanism, overcoming the disadvantages of published catalysts in the ability to regulate the mass of resulting polymer products with low dispersion index (PDI, which is an indicator of the uniform distribution of polymers). The synthesis of polymers such as polymethylmethacrylate, polybenzylmethacrylate, or polystyrene under fluorescent lamps in the presence of MOF-902 catalyst can be produced industrially large scale.