RESUMEN
There is a demand to develop molecular catalysts promoting the hydrogen evolution reaction (HER) with a high catalytic rate and a high tolerance to various inhibitors, such as CO and O2 . Herein we report a cobalt catalyst with a penta-dentate macrocyclic ligand (1-Co), which exhibits a fast catalytic rate (TOF=2210â s-1 ) in aqueous pHâ 7.0 phosphate buffer solution, in which proton transfer from a dihydrogen phosphate anion (H2 PO4 - ) plays a key role in catalytic enhancement. The electrocatalyst exhibits a high tolerance to inhibitors, displaying over 90 % retention of its activity under either CO or air atmosphere. Its high tolerance to CO is concluded to arise from the kinetically labile character of undesirable CO-bound species due to the geometrical frustration posed by the ligand, which prevents an ideal trigonal bipyramid being established.
RESUMEN
The reduction of carbon dioxide (CO2 ) has been considered as an approach to mitigate global warming and to provide renewable carbon-based fuels. Rational design of efficient, selective, and inexpensive catalysts with low overpotentials is urgently desired. In this study, four cobalt(II) tripodal complexes are tested as catalysts for CO2 reduction to CO in a MeCN/H2 O (4:1â v/v) solution. The replacement of pyridyl groups in the ligands with less basic quinolinyl groups greatly reduces the required overpotential for CO2 -to-CO conversion down to 200-380â mV. Benefitting from the low overpotentials, a photocatalyst system for CO2 -to-CO conversion is successfully constructed, with an maximum turnover number (TON) of 10 650±750, a turnover frequency (TOF) of 1150±80â h-1 , and almost 100 % selectivity to CO. These outstanding catalytic performances are further elucidated by DFT calculations.