MOF Based Single-Site Cooperative Catalysis for CO2 Hydrogenation

Utviklingen av enkelt-atoms katalysatorer som kan transformere CO2 til verdifulle produkter har vært målet for CO2pCat-prosjektet. Et av hovedmålene var å forstå de intrikate trinnene i hydrogenasjonen av CO2 til alkoholer, ved å kombinere beregningsmetoder og eksperimenter. For dette formålet ble flere katalytiske systemer studert, inkludert nanoporøse materialer og molekylære katalysatorer. Til tross for vanskeligheter, ble det gjort avgjørende fremskritt i utviklingen av protokoller for å modellere disse reaksjonene ved hjelp av mikrokinetiske modeller og kombinere resultatene fra flere beregningsmodeller. Ved å utnytte kraften i maskinlæring, satte CO2pCat seg som mål å designe pincer-katalysatorer for deres integrering i UiO-type metall-organiske rammeverk. En utfordring var den begrensede diversiteten av tilgjengelige strukturer, som motiverte opprettelsen av et pincer-ligand-bibliotek basert på organometalliske komplekser fra Cambridge-strukturelle databasen. Fullføringen av dette biblioteket og utnyttelsen av det for design av (de-)hydrogenasjonsreaksjoner er et pågående arbeid. Uansett, fremskritt ble gjort i syntesen av Mn-komplekser med pincer-ligander som kunne integreres i metall-organiske rammeverk. Selv om disse kompleksene ikke er aktive for CO2-hydrogenasjonsreaksjoner, skaper deres kapasitet for lån av hydrogen-reaksjoner nye veier for fremtidige anvendelser. Oppsummert har CO2pCat-prosjektet lagt et sterkt grunnlag for fremtidige studier innen bærekraftig kjemi, og banet vei for innovative løsninger på miljøutfordringer.

1) We have developed a protocol to synthesize MOF-based single-atom catalysts with acid-based functionalities that can be used for (de-)hydrogenation reactions (Manuscript in preparation). Preliminary results for CO2 hydrogenation reactions showed the limitations of these catalysts. These results provide guidelines for future catalyst design and protocols for the synthesis of MOFs for (de-)hydrogenation reactions. 2) We have generated mechanistic insight into hydrogenation reactions using nanoporous materials, graphene-based single-atom catalysts, and bifunctional homogeneous catalysts, which will be used to further develop these reactions. These results have been published in four articles, which have already been cited (19 citations). 3) We are finalizing a library of pincer ligands for bifunctional catalysts, which will be used to optimize (de)-hydrogenation reactions. This result has already facilitated one successful project application to exploit this library. 4) We have developed computational protocols combining experiments and theory for studying complex reaction mechanisms, including multi-component catalysts. This work will strongly impact future mechanistic studies involving homogeneous and heterogeneous catalysis. These results have been published in one article and one review with 15 citations.

One of the main challenges of the 21st century is the reduction of CO2 emissions into the atmosphere by replacing fossil fuels with renewable energy sources. The CO2pCat research project aims at developing a multivariate metal organic framework (MTV-MOF) involving functionalized linker cooperation for the selective hydrogenation of CO2 to methanol. Methanol is a versatile liquid and an ideal CO2 derivative when made by renewable hydrogen sources. However, efforts to perform this reaction with heterogeneous and homogeneous catalysts under mild conditions have failed at achieving high conversion with high selectivity. A combined approach, immobilizing well-defined molecular catalysts on porous materials has only yielded reduction of CO2 to formate. The use of MOFs with Cu(I) functionalized Zr-nodes leads to ethanol and requires a photosynthesizer to stabilize the catalyst. In CO2pCat, these limitations will be overcome by using linkers able to: 1) hold, and stabilize the active catalyst; 2) promote the cooperative activation of H2 via metal-ligand bifunctionality; and 3) promote the cooperative hydrogenation of formic acid via catalyst-amine cooperation. In order to achieve these goals, state-of-the-art computational methods and machine learning techniques will be used to design these linkers. The systems designed in silico will be implemented experimentally by using the recent advances in MOF synthesis by postsynthetic strategies. Computational methods combined with kinetic experiments will be used to get mechanistic insight into the cooperative activation of H2 and formic acid on reported and newly developed systems. In total, CO2pCat will provide chemical understanding on CO2 hydrogenation processes, a large database of catalyst-linkers able to hydrogenate CO2, and a single-site heterogeneous catalyst for the hydrogenation of CO2 to methanol.