Turning it off! Disfavouring hydrogen evolution to enhance selectivity for CO production during homogeneous CO reduction by cobalt-terpyridine complexes.

Understanding the activity and selectivity of molecular catalysts for CO reduction to fuels is an important scientific endeavour in addressing the growing global energy demand. Cobalt-terpyridine compounds have been shown to be catalysts for CO reduction to CO while simultaneously producing H from the requisite proton source. To investigate the parameters governing the competition for H reduction CO reduction, the cobalt bisterpyridine class of compounds is first evaluated as H reduction catalysts. We report that electronic tuning of the ancillary ligand sphere can result in a wide range of second-order rate constants for H reduction. When this class of compounds is next submitted to CO reduction conditions, a trend is found in which the less active catalysts for H reduction are the more selective towards CO reduction to CO. This represents the first report of the selectivity of a molecular system for CO reduction being controlled through turning off one of the competing reactions. The activities of the series of catalysts are evaluated through analysis and a catalytic Tafel plot is provided.