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US-12616966-B2 - Metal organic framework and use thereof for generating H2

US12616966B2US 12616966 B2US12616966 B2US 12616966B2US-12616966-B2

Abstract

The present invention relates to metal-organic frameworks (MOFs) which contain trimetallic centres with pyrazole as a ligand in the structure thereof. Particularly, it relates to MOFs which contain units of formula (I). The present invention also relates to a photocatalytic method for generating H2 starting from liquid water or vapour using said materials.

Inventors

  • Sergio NAVALÓN OLTRA
  • Cristina Vallés García
  • María Cabrero Antonino
  • Hermenegildo García Gómez
  • Christian SERRE
  • Georges MOUCHAHAM
  • Lin Zhou

Assignees

  • PARIS SCIENCES ET LETTRES
  • ECOLE SUPERIEURE DE PHYSIQUE ET DE CHIMIE INDUSTRIELLES DE LA VILLE DE PARIS
  • CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUE
  • ECOLE NORMALE SUPERIEURE

Dates

Publication Date
20260505
Application Date
20211005
Priority Date
20201005

Claims (9)

  1. 1 . A photocatalytic method for producing hydrogen starting from water comprising the use of a catalyst that is a metal organic framework characterized in that it comprises units of formula (I) in the structure thereof: wherein M 1 , M 2 and M 3 are metal cations selected from the list consisting of Co and Cu, wherein M 1 , M 2 and M 3 are equal to each other; X is a substituent selected from the list consisting of: H, CH 3 , OCH 3 , SO 3 − , F, Cl, Br, I, NH 2 , and CF 3 ; Y is COO − ; Z is a substituent selected from the list consisting of: H, CH 3 , OCH 3 , SO 3 − , F, Cl, Br, I, NH 2 , and CF 3 ; L 1 , L 2 , L 3 and L 4 are groups independently selected from the list consisting of: O 2 − , OH − , H 2 O and halide; n 1 , n 2 , n 3 and n 4 are numbers independently selected from 0 and 1, and contacting the metal-organic framework, with water in liquid or vapor state and in the presence of sunlight or artificial light.
  2. 2 . The photocatalytic method, according to claim 1 wherein X is H and Z is other than H.
  3. 3 . The photocatalytic method, according to claim 1 wherein X and Z are H.
  4. 4 . The photocatalytic method, according to claim 1 , wherein L 1 , L 2 , L 3 and L 4 are independently selected from Cl − and OH − .
  5. 5 . The photocatalytic method, according to claim 1 , wherein M 1 , M 2 and M 3 are Cu cations; X and Z are H, Y is —CO 2 H and L 1 , L 2 , L 3 and L 4 is Cl − , OH − or is not present.
  6. 6 . The photocatalytic method, according to claim 1 , wherein the proportion of units of formula (I) in the structure is between 15% and 100%, in moles with respect to the total of ligands.
  7. 7 . The photocatalytic method, according to claim 1 , wherein metal-organic framework contains one or more species housed in the pores which act as cocatalysts favouring the H 2 photocatalytic generation reaction wherein said cocatalysts are selected from the list consisting of: nanoparticles of the metals platinum, gold, iridium, silver, rhodium and nickel, palladium and combinations thereof, nanoparticles of metal oxides that are selected from cobalt, copper, ruthenium, molybdenum, strontium, zirconium and combinations thereof,- nanoparticles of metal chalcogenides based on sulphides, selenides or tellurides combined with molybdenum, cadmium, zinc, lead, indium, copper, tungsten and combinations thereof,- and metal complexes wherein the metal is chrome, manganese, iron, cobalt, nickel, copper, ruthenium, rhodium, palladium, silver, platinum and iridium and the organic ligand contains amine-, imine- or heterocyclic-type nitrogen atoms, and combinations thereof.
  8. 8 . The photocatalytic method according to claim 1 wherein the metal-organic framework is deposited in the form of a thin film between 1 and 20 microns thick and a bed of water between 0.5 and 12 cm thick is made to flow over said film at a temperature between 4 and 40° C. and at a rate between 0.1 and 2 ml/hour, said film being exposed to sunlight or artificial light.
  9. 9 . The photocatalytic method according to claim 1 wherein the metal-organic framework is deposited in the form of a thin film several microns thick and a flow of water vapor at a temperature between 10° and 150° C. is made to flow over said film at a rate between 0.1 and 2 ml/hour and wherein said film is exposed to sunlight or artificial light.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS AND PRIORITY This patent application claims priority from PCT Application No. PCT/EP2021/077404 filed Oct. 5, 2021, which claims priority from European Patent Application No. 20382882.7 filed Oct. 5, 2020. The present invention describes metal-organic frameworks which contain ligands (or connectors between metal nodes) formed by trimetallic centres linked to pyrazole in the structure thereof, as well as the use thereof for generating H2 under exposure to sunlight. STATE OF THE ART Metal-organic frameworks (MOFs) are crystalline and porous materials the structure of which is formed by nodes which contain one or more metal atoms that are linked by coordination bonds and coulombic interactions with rigid organic ligands. The metal nodes of those MOFs which are made up by units of M6O4(OH)412− are known in the state of the art, wherein M is a tetrapositive metal cation such as for example Zr+4, Ce4+ and Hf4+ and the organic ligands are tricarboxylic aromatic compounds such as trimesic acid and 1,3,5- (4-carboxyphenyl)benzene (Liu, Q. et al. Mesoporous Cages in Chemically Robust MOFs Created by a Large Number of Vertices with Reduced Connectivity. Journal of the American Chemical Society 2019, 141, 488-496). These components define a porous structure that corresponds to a solid with an X-ray diffraction such as that indicated in FIG. 1 accompanying this document. These MOFs materials possess different properties that derive from the surface area and composition thereof, among which are the high gas adsorption capacity and catalytic activity thereof. More directly related to the present invention, it is known in the state of the art that some MOF materials exhibit photocatalytic activity when these materials are irradiated with photons the wavelength of which corresponds to the UV-Visible or near-IR region, capable of promoting chemical reactions. A particular case of the use of MOFs as photocatalysts relates to the case in which the source of irradiation is natural sunlight that reaches the earth's surface. The spectrum of solar radiation on the earth's surface corresponds to a photon distribution with wavelengths in the UV region greater than 380 nm which corresponds to around 4% of the total energy, in addition to photons in the visible region between 400 and 800 nm which contributes approximately 48%, to solar energy and to the rest of lower energy photons in the near-IR area. Among the photocatalytic reactions that have been described for MOF-type metal-organic materials, of special relevance in the present invention, is the generation of H2 by irradiation of these materials in contact with water, either in liquid or vapour phase. A particular case for which there are few precedents is the photocatalytic generation of H2 using distilled water, fresh water or seawater and H2 and O2 are simultaneously generated in the amounts corresponding to the water composition. Processes of this type are known in the state of the art as photocatalytic water splitting and the evidence described indicates that water behaves simultaneously as an electron donor and acceptor compound. The reaction that takes place in the photocatalytic water splitting is indicated in the following equation which also includes the enthalpy variation of the process. H2O→H2+½O2 ΔH=+285.85 kJ In the context of non-fossil-fuel based renewable energies, the above reaction can serve as a way to transform sunlight as a primary source of energy into chemical energy, specifically into H2 which can be used as an energy vector in fuel cells or in combustion systems. Additionally, H2 can serve as a chemical reagent in hydrogenation or reduction reactions. Nevertheless, despite the potential of the photocatalytic generation of H2 starting from H2O, the situation in the state of the art describes MOF materials having a very poor and still insufficient efficiency to be used in any industrial process (A. Dhakshinamoorthy, Z. Li, H. Garcia., Catalysis and photocatalysis by metal organic frameworks, Chem. Soc. Rev. 2018, 47, 8134-8172). Furthermore, the MOF-type photocatalysts described need noble metals and particularly platinum to increase the photocatalytic performance thereof in the generation of H2. As platinum is a high-priced metal, the inclusion thereof in MOF materials makes the material significantly more expensive and reduces the economic attractiveness of the process. Additionally, the photocatalytic activity of the MOF materials described to date decreases considerably below 50% of the efficiency thereof when the radiation is exclusively carried out with visible light and not with ultraviolet light, so the solar radiation of these materials is very inefficient. In view of the state of the art, it is considered important to develop MOF materials as photocatalysts for the efficient generation of H2 in which the presence of noble metals in the composition thereof are not necessary and the photocatalytic response