Porous soldis as macroligands for heterogenized molecular catalysis
Résumé
The integration of the catalytically active centers into a solid support without loss of performance compared to the homogeneous analog is still a major challenge. In this context, a molecularly defined support as macroligand, i.e. a solid acting like the ligand in the corresponding molecular complex, can be considered as a key to bridge the gap between molecular and heterogeneous catalysis. Metal-Organic Frameworks (MOF) and purely organic microporous polymers are promising candidates.[1,2]
Here we present series of heterogeneous catalysts based on MOFs and microporous polymers used as macroligands for heterogenized organometallic complexes. We show that both homogeneous and heterogenized catalysts follow the same linear correlation between the electronic effect of the ligand, described by the Hammett parameter, and the catalytic activity. The general linear trend gives also insight into the contribution of the diffusion limitation inside the porous network of such heterogeneous catalyst. The rational design of heterogenized catalysts can thus be guided by molecular chemistry rules.
The conception of highly efficient heterogeneous catalyst based on porous polymer support and driven by the Hammett parameter of bipyridine-chelating macroligand is demonstrated here for two Rh-catalyzed reactions: The photoreduction of carbon dioxide with turnover frequencies (TOF) up to 28 h-1,[1] among the highest reported for heterogeneous photocatalytic formate production and the transfer hydrogenation reaction of α-aryl ketones with TOFs of up to 3.3 h-1.[2]
[1]. F. M. Wisser, P. Berruyer, L. Cardenas, Y. Mohr, E. A. Quadrelli, A. Lesage, D. Farrusseng, J. Canivet, ACS Catal. 2018, 8, 1653-1661.
[2]. F. M. Wisser, Y. Mohr, E. A. Quadrelli, D. Farrusseng, J. Canivet, ChemCatChem 2018, DOI: 10.1002/cctc.201701836.