Device and method for producing highly porous, crystalline surface coatings

Abstract

The present invention relates to a device, the use thereof and a method for producing highly porous, crystalline surface coatings comprising at least two spraying devices operating in sequential sequence for applying coating agents from the storage vessels (3, 4) to a material arranged on a sample holder (1) and at least one rinsing device (5, 13, 16) for removing unbound molecules from the coated surface.

Claims

1. A method of producing a surface coating, wherein the method comprises: (a) sequentially applying precursor substances for the coating to a surface of a carrier material by spraying devices while supplying carrier gas from a storage container to provide a coated surface, (b) removing unbound molecules from the coated surface of (a) by at least one rinsing device, (c) sequentially applying further precursor substances for the coating to a rinsed surface of (b), (d) removing unbound molecules from the coated surface of (c) by the at least one rinsing device, and (e) repeating (c) and (d) until a desired thickness of the surface coating is achieved; and wherein substances which afford a surface coating that is crystalline and has a structure of a metal-organic framework and/or a porosity of between 8 and 50 Å are employed as precursor substances.

2. The method of claim 1, wherein at least two different precursor substances are employed.

3. The method of claim 2, wherein one of the precursor substances comprises an organic component and another one of the precursor substances comprises metal ions.

4. The method of claim 3, wherein the organic component comprises a carboxylate compound.

5. The method of claim 3, wherein the organic component comprises a pyridine compound.

6. The method of claim 3, wherein the organic component comprises at least one of 1,3,5-benzenetricarboxylic acid, 1,4-benzenedicarboxylic acid, and naphthalenedicarboxylic acid.

7. The method of claim 3, wherein the metal ions comprise at least one of Cu(II), Zn(II), and Fe(III).

8. The method of claim 3, wherein metal ions are present as acetates.

9. The method of claim 1, wherein the precursor substances are present in dissolved form.

10. The method of claim 9, where the precursor substances are dissolved in one or more of ethanol, water, and DMF.

11. The method of claim 9, wherein the precursor substances are applied as liquid drops which are finely distributed in the carrier gas.

12. The method of claim 11, wherein the carrier gas is an inert gas.

13. The method of claim 12, wherein the carrier gas comprises one or more of nitrogen, argon, and helium.

14. The method of claim 1, wherein one or more of ethanol, water, and DMF are used as rinsing agents.

15. The method of claim 1, wherein the coating has a structure of a metal-organic framework.

16. The method of claim 1, wherein the coating has a porosity of between 8 and 50 Å.

17. A method of producing a surface coating, wherein the method comprises: (a) sequentially applying at least two different precursor substances of the coating, at least one of which comprises an organic component selected from carboxylates and pyridine compounds and at least one of which comprises metal ions selected from one or more of Cu(II), Zn(II), and Fe(III) to a surface of a carrier material by spraying devices while supplying inert carrier gas from a storage container to provide a coated surface, (b) removing unbound molecules from the coated surface of (a) by at least one rinsing device and using at least one of ethanol, water and DMF as rinsing agent, (c) sequentially applying further precursor substances used in (a) to a rinsed surface of (b), (d) removing unbound molecules from the coated surface of (c) by at least one rinsing device and using at least one of ethanol, water and DMF as rinsing agent, and (e) repeating (c) and (d) until a desired thickness of the surface coating is achieved; and wherein substances which afford a surface coating that is crystalline and has a structure of a metal-organic framework and a porosity of between 8 and 50 Å are employed as precursor substances.

18. The method of claim 17, wherein metal ions are present as acetates.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention is explained in more detail below with reference to the figures:

(2) FIG. 1 shows an example of a system that can be used according to the invention.

(3) FIG. 2 shows the result of the X-ray diffractogram according to Example 1 (HKUST-1 (40 layers) on a COOH-functionalized surface).

(4) FIG. 3 shows the X-ray diffractogram according to Example 2 (Cu.sub.2(bdc).sub.2 MOF (40 layers) on a COOH-functionalized surface).

(5) FIG. 4 shows the X-ray diffractogram according to Example 3 (Cu.sub.2(bdc).sub.2(dabco) MOF (20 layers) on a pyridine-functionalized surface).

(6) The reference numerals in FIG. 1 have the following meaning: 1 Temperature-controllable and movable vacuum holding unit. 2 Gas bottle for inert gas. 3 Feed vessel for the precursor substance containing component A. 4 Feed vessel for the precursor substance containing component B. 5 Feed for rinsing solution. 6 Perforated baseplate. 7 Connection for the suction removal of gas. 8 Drain for liquids. 9 PC with control software. 10 Valve-testing or testing distributor with communication to the PC. 11 Spraying device for the precursor substance containing component A. 12 Spraying device for the precursor substance containing component B. 13 Outlet nozzle for rinsing solution. 14 Wall lead-through with quick connectors. 15 Temperature-controllable climatically controlled chamber. 16 Pump for rinsing solution. 17 Nitrogen supply for compressed-air valves. 18 Control block for compressed-air valves.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

(7) Using an inert gas 2, the spraying devices 11 and 12 can nebulize the precursor substances with the components A and B onto a surface without any droplets. The components A and B are chemical compounds that are different from one another. For example, A may be the organic component and B may be the component containing metal ions. These are applied separately by way of the spraying device 11 and 12, i.e. component A by way of the spraying device 11 and component B by way of the spraying device 12. With its feed 5 and the pump 16, the rinsing device 13 allows the supply of rinsing solution for the complete removal of unbound precursor molecules, without the sprayed-on layers being adversely influenced. For this, rinsing solution is applied to the coated surface from the feed 5 by means of the pump 16.

(8) The spraying devices 11 and 12 are connected to the storage vessels 3 and 4. By supplying carrier gas from the storage container 2, solution of precursor substances is sucked in from the storage containers 3 and 4 on the principle of an aspirator. The opening of the precursor substance supply at the spraying devices 11 and 12 is performed by way of compressed-air-controlled regulating valves. On the other hand, the supply of carrier gas may take place by way of the computer-controlled process controller 9 and 10. Here, the device 10 is a valve or spray distributor, which is controlled by way of a PC 9.

(9) The material of which the surface is to be coated is mounted vertically on the sample holder 1. The material is sucked against it by means of negative pressure.

(10) The rinsing device 13 is arranged in such a way that rinsing agent emerging from it runs along on the surface of the coated material from the upper end and thus unreacted precursor substance molecules are rinsed off. Running-off rinsing solutions run away by way of the perforated baseplate 6. The liquids can be removed by suction by way of the opening 8.

(11) In the system according to the invention as shown in FIG. 1, the sample holder 1, the rinsing device 13 and the coating devices 11 and 12 are arranged in a climatically controlled chamber 15, in which the temperature and atmospheric humidity can be monitored and regulated.

(12) The device as shown in FIG. 1 also includes structural elements for the use of volatile precursor substance solvents, for example of ethanol. For this, the suction removal device 7 is provided. In other words, by means of this device, the climatically controlled chamber 15 can be purged by means of nitrogen, in order to avoid the formation of explosive gas mixtures.

(13) All of the connections to the climatically controlled chamber can be accomplished by way of the quick couplings 14.

Example 1

(14) Production of the MOF Cu.sub.3(btc).sub.2×H.sub.2O HKUST-1 (40 layers) on a COOH-functionalized surface (btc=1,3,5-benzenetricarboxylic acid; HKUST=Hong Kong University of Science and Technology).

(15) As preparation for the test, a self-assembled monolayer (SAM) was produced on a gold-coated piece (about 15×20 mm) of a silicon wafer by dipping into a mercaptohexadecanoic acid (MHDA) solution for 48 hours. After dipping, the sample was rinsed with ethanol and subsequently dried with nitrogen.

(16) For the spraying process, firstly Cu(CH.sub.3COO).sub.2 solution was sprayed onto the SAM for 15 seconds. As a second substance, BTC (benzenetricarboxylic acid) was sprayed on for 25 seconds. Between each spraying step, the sample was rinsed with ethanol. Altogether, 40 cycles of the sequence described were carried out. The resultant sample was dried and analyzed by means of XRD. The resultant X-ray diffractogram shows two sharp intensity peaks, which are evidence of the strictly crystalline and spatially ordered character of the layer formed. The corresponding layers consist of 40 layers.

Example 2

(17) Production of the MOF Cu.sub.2(bdc).sub.2 (40 layers) on a COOH-functionalized surface (bdc=benzenedicarboxylic acid).

(18) As preparation for the test, a SAM was produced on a gold-coated piece (about 15×20 mm) of a silicon wafer by dipping into a mercaptohexadecanoic acid (MHDA) solution for 48 hours. After dipping, the sample was rinsed with ethanol and subsequently dried with nitrogen.

(19) For the spraying process, firstly Cu(CH.sub.3COO).sub.2 solution was sprayed onto the SAM for 15 seconds. As a second substance, bdc (bdc=1,4-benzenedicarboxylic acid) was sprayed on for 25 seconds. Between each spraying step, the sample was rinsed with ethanol. Altogether, 40 cycles of the sequence described were carried out. The resultant sample was dried and analyzed by means of XRD. Altogether, a 40-layer coating was obtained. The resultant very sharp intensity peaks also provide evidence for this second MOF type of the strictly crystalline and spatially ordered character of the layer formed.

Example 3

(20) Production of the MOF Cu.sub.2(ndc).sub.2 (dabco) (20 layers) on a pyridine-functionalized surface (20 cycles [Cu.sub.2(ndc).sub.2 (dabco)] on pyridine SAM).

(21) As preparation for the test, a SAM was produced on a gold-coated piece (about 15×20 mm) of a silicon wafer by dipping into a 4,4-pyridyl-benzenemethanethiol (PBMT) solution for 48 hours. After dipping, the sample was rinsed with ethanol and subsequently dried with nitrogen.

(22) For the spraying process, firstly Cu(CH.sub.3COO).sub.2 solution was sprayed onto the SAM for 15 seconds. As a second substance, a 1:1 mixture of ndc (ndc=naphthalenedicarboxylic acid) and dabco=1,4-diazabicyclo[2.2.2]octane was sprayed on for 25 seconds.

(23) Between each spraying step, the sample was rinsed with ethanol.

(24) Altogether, 20 cycles of the sequence described were carried out. The resultant sample was dried and analyzed by means of XRD.

(25) Altogether, a 20-layer coating was obtained.

(26) In this example, a different spatial orientation of the crystal lattice produced was achieved by modifying the SAM used as a basis.