Selectivity Effects in Bimetallic Catalysis: Role of the Metal Sites in the Decomposition of Formic Acid into H₂ and CO₂ by the Coinage Metal Binuclear Complexes [dppmMM′(H)]⁺

Abstract

Design of new bimetallic catalysts requires an understanding of how cooperative effects of the metal sites influences reactivity. Here we show how switching one or both of the silver atoms in binuclear silver hydride cations, [dppmAg2(H)]+ (dppm=1,1‐Bis(diphenylphosphino)‐methane), with all combinations of copper and/or gold maintains selective dehydrogenation of formic acid, enhancing reactivity by up to 2 orders of magnitude. This is a key step in the selective, catalyzed extrusion of carbon dioxide from formic acid, HO2CH, with important applications in hydrogen storage and in situ generation of H2. Decarboxylation of [dppmMM′(O2CH)]+ through collision induced dissociation regenerates [dppmMM′(H)]+. DFT calculations provide insights into these cooperative effects. The copper homobinuclear catalyst performs best overall.

Selective C−O Coupling Hidden in the Thermal Reaction of [Al2CuO5]+ with Methane

“…Further, upon reaction with NH 3 , the clusters [Cu 4 O 2 ] + , [Cu 5 O 3 ] + , [Cu 6 O 3 ] + , [Cu 7 O 3 ] + , and [Cu 7 O 4 ] + give rise to the release of H 2 O, whereas [Cu 7 O 5 ] + affords the generation of neutral HNO . In addition, the copper complex [(dppm)Cu 2 (H)] + (dppm=1,1‐bis(diphenylphosphino)‐methane) selectively decomposes formic acid into H 2 and CO 2 , and the structurally more simple copper hydrides [CuH 2 ] − and [Cu 2 H 3 ] − also exhibit versatile reactivities towards a series of small neutral molecules; finally, the [LCuO] + (L=1,10‐phenanthroline) complex reacts with fluoromethanes to give H/O atom transfers . In addition to these gas‐phase ion/molecule reactions, there also exist a large number of studies dealing with gas‐phase isomerization of Cu complexes .…”

Models Facilitating the Design of a New Metal‐Organic Framework Catalyst for the Selective Decomposition of Formic Acid into Hydrogen and Carbon Dioxide

“…Although the exact nature of the stoichiometry of the solution phase catalysts is unknown, subsequent gas phase studies highlighted that tetranuclear silver hydride cluster complexes were unreactive towards formic acid . This spurred us onto examining the role of the metal center, where all possible homo and hetero coinage metal complexes were explored to establish that the best gas‐phase catalyst for both steps in the catalytic cycle was the biscopper complex 1 b . Given the difficulty of establishing the nature of the solution phase catalyst, we were interested in translating the gas‐phase homogeneous catalysts into a heterogenous system.…”

How to Translate the [LCu2(H)]+‐Catalysed Selective Decomposition of Formic Acid into H2and CO2from the Gas Phase into a Zeolite.

“…Here we use a combination of theory and gas‐phase experiments to establish the requirements to “heterogenize” our recently designed phosphine ligated coinage metal hydrides for the catalytic and selective gas‐phase decomposition of formic acid into carbon dioxide and hydrogen [Eq. ], a reaction crucial for the use of formic acid in hydrogen storage applications …”

“…Decarboxylation of [(L)M1M2(O 2 CH)] + by collision‐induced dissociation (CID) regenerates the catalyst [(L)M1M2(H)] + (Scheme , step II). The nature of the bisphosphine ligand, metal and stoichiometry were all found to play key roles, with [(dppm)Cu 2 (H)] + (dppm=1,1‐bis(diphenylphosphino)‐methane) emerging as the most effective catalyst …”

“…The natureo ft he bisphosphine ligand, [5] metal [6] and stoichiometry [7] were all found to play key roles, with [(dppm)Cu 2 (H)] + (dppm = 1,1-bis(diphenylphosphino)-methane) emerging as the most effective catalyst. [6] Although ar ange of "ship-in-a-bottle" catalysts that entrap a metal complex in the nanocavity of az eolite have been prepared, [9,10] the transformation of ag as-phase catalyst into a zeolitef ramework has not previously been considered. Conceptually,t his requires aj oint approach using theory and gasphase experiments to find the catalyst that best fits into the zeolitew hilst still maintaining its reactivity.…”