The development of molecular catalysts for CO2 electroreduction within electrolyzers requests their immobilization on the electrodes. While a variety of methods have been explored for the heterogenization of homogeneous complexes, a novel approach using a hierarchical porous carbon material, derived from a metal-organic framework, is reported as a support for the well-known molecular catalyst [Re(bpy)(CO)3 Cl] (bpy=2,2'-bipyridine). This cathodic hybrid material, named Re@HPC (HPC=hierarchical porous carbon), has been tested for CO2 electroreduction using a mixture of an ionic liquid (1-ethyl-3-methylimidazolium tetrafluoroborate, EMIM) and water as the electrolyte. Interestingly, it catalyzes the conversion of CO2 into a mixture of carbon monoxide and formic acid, with a selectivity that depends on the applied potential. The present study thus reveals that Re@HPC is a remarkable catalyst, enjoying excellent activity (turnover numbers for CO2 reduction of 7835 after 2 h at -1.95 V vs. Fc/Fc+ with a current density of 6 mA cm-2 ) and good stability. These results emphasize the advantages of integrating molecular catalysts onto such porous carbon materials for developing novel, stable and efficient, catalysts for CO2 reduction.
Keywords: CO2 electroreduction; catalysis; heterogenization; hierarchical porous carbon; ionic liquid; rhenium complex.
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