Immobilization of a Molecular Re Complex on MOF-derived Hierarchical Porous Carbon for CO₂ Electroreduction in Water/Ionic Liquid Electrolyte

The development of molecular catalysts for CO 2 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 CO 2 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 CO 2 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 CO 2 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 CO 2 reduction.