CAMOCAT - Development of novel MOF-carbon nitride hybrid compounds for flow/gas-phase photocatalytical reduction of CO2 to CO under capillary condensation conditions

• Applicant: Dr. Patrick Nimax
• Subject Area: Solid State and Surface Chemistry, Material Synthesis ; Inorganic Molecular Chemistry - Synthesis and Characterisation ; Chemical and Thermal Process Engineering ; Polymer Materials
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 536994323

Photocatalysed reactions have gained interest due to a shift towards a transition to greener societies and energy sources. With high energy prices impacting the highly energy-dependant chemistry industry, alternative catalytic approaches for fuel generation have come into focus. The direct use of sun-energy avoids intermediate steps, turning it cheaper than electrocatalysis. Carbon nitrides (CNs) recently showed attractive features in photocatalytic applications for waste treatment and fuel production. Unlike analogues such as graphene comparable in terms of structure and band gap, graphitic CNs possess low porosity that hinder substrate adsorption in catalysis. A high surface area, however, is key for environmentally-relevant reactions such as gas-phase CO2 reduction. Heterojunction compounds with Metalorganic Frameworks (MOFs) can positively contribute to meaningful photocatalytic applications with a variety of functions. Separating reduction and oxidation reactions occurring after photoexcitation leads to higher efficiency. The high versatility of MOF@CN composites however introduces many factors affecting photocatalysis that this proposal is aiming to adress. As its goal, CAMOCAT will explore how improved MOF@CN composites designed for the application in a VIS-light active heterojunction compound perform in photocatalyzed CO2 reduction to yield CO in flow/gas-phase reactors under visible light and capillary solvation conditions. This will be achieved on several levels: 1)by modifying the MOF component with functional groups that will enhance VIS light absorption and charge transfer over the interface of the heterojunction while attempting to stabilize free radicals in the MOF component. By doing so, electron hole separation will be improved, while catalytic activity will be enhanced by utilizing the metal centers of the MOF. 2)by using mesoporous CN materials featuring large surface areas and consistent pore sizes achieved through the use of chemical vapour deposition on porous silica template that is then removed, leaving mesoporous CN with pore diameters of 10-200 nm for MOF deposition. 3)by using capillary solvation in gas phase photocatalysis, catalytic efficiency can be improved. Capillary condensation is a function of temperature, partial pressures and pore size. By modulating CN pore sizes through control of the MOF layer thickness, the conditions for capillary solvation can be tuned to allow higher throughput at higher pressures. 4)by utilizing dia- and paramagnetic MAS-NMR to identify differences in MOF deposition on CN. Preliminary results have shown the effectivity of NMR to check for correct deposition in MOF@CN composites. More sensitive than PXRD, it can identify non-deposited MOF, as well as differences in deposition mehods. These approaches will allow a comparative study to investigate the interactions in MOF@CN composites, as well as improve on current literature to create a more efficient photocatalytic system.

• DFG Programme: WBP Fellowship
• International Connection: Italy, Spain
• Hosts: Professor Dr.-Ing. Pedro L. Arias; Professor Dr. Davide Ravelli