Molecular Iridium Complexes in Metal–Organic Frameworks Catalyze CO₂ Hydrogenation via Concerted Proton and Hydride Transfer

Abstract

Molecular iridium catalysts immobilized in metal-organic frameworks (MOFs) were positioned in the condensing chamber of a Soxhlet extractor for efficient CO hydrogenation. Droplets of hot water seeped through the MOF catalyst to create dynamic gas/liquid interfaces which maximize the contact of CO, H, HO, and the catalyst to achieve a high turnover frequency of 410 h under atmospheric pressure and at 85 °C. H/D kinetic isotope effect measurements and density functional theory calculations revealed concerted proton-hydride transfer in the rate-determining step of CO hydrogenation, which was difficult to unravel in homogeneous reactions due to base-catalyzed H/D exchange.

Metal–Organic Frameworks-Based Catalysts for Biomass Processing

“…The adequate solution of this problem is fine tuning of the MOF structures and porosity for a specific catalytic process. Among the possible routes to introduce the supplementary active sizes in MOF host matrices, one can use the direct synthesis by careful choice of organic and inorganic building blocks or their post-synthetic functionalization (PSM) [38], grafting of active groups on the open metal sites [39] and encapsulation of active species like metal and metal oxide nanoparticles as well as small molecules (active homogeneous catalysts) in the pore voids [26,[40][41][42]. The diversity of the modification routes distinguishes MOFs from other nanoporous materials such as zeolites and activated carbons.…”

Metal-organic framework membranes with single-atomic centers for photocatalytic CO2 and O2 reduction

“…To the contrary, no significant HCOO* peaks could be found in the FTIR spectra for the bare d-aUiO catalyst ( Figure S27b). Therefore, a plausible reaction route for photocatalytic CO2RR on Ir1/d-aUiO would be that the CO2 molecules were first adsorbed by the d-aUiO to form surface carbonic acid species and then hydrogenated on the Ir1 catalytic centers with photogenerated electrons provided by the d-aUiO matrix and protons (from water) to form HCOOH 34,35 . Interestingly, similar photocatalytic CO2RR route for HCOOH production can be also enabled on other Ir/MOF catalysts.…”

Cyclometalation of lanthanum(iii) based MOF for catalytic hydrogenation of carbon dioxide to formate

“…14 Recently, there has been a growing interest in the use of MOFs for conversion of CO 2 to useful chemicals. The majority of these studies have been focusing on water stable Zr-based MOFs, 12,[15][16][17][18][19][20][21] with the catalytically active centres introduced to the MOF backbone by post synthetic metalation of a bipyridine linker. Interestingly, none of these publications report on the activity of the parent MOF towards reduction of CO 2 but rather focus on the metals introduced into the pores of the MOF such as ruthenium, rhodium and iridium.…”