Non-synergistic photocatalysis of CO2-to-CO conversion by a binuclear complex of rigidly linking two cobalt catalytic centers

Abstract

A novel binuclear cobalt complex C1 of rigidly linking two [Co(TPA)Cl]Cl moieties at meta positions of a benzene was synthesized and characterized as a catalyst for homogeneous photocatalytic CO2 reduction. Different from state-of-the-art binuclear catalyst catalyzing CO2 reduction with a synergistic catalysis mechanism, C1 catalyses CO2-to-CO conversion independently at each cobalt catalytic center. At an optimal condition, system of C1 produced CO with a TON of 721 (based on C1, corrsoponding to TON 360 per cobalt center) and a high selectivity of 91.5%. Electrochemistry and steady state spectroscopy studies revealed that a CoICoI species, generated via successive photoinduced electron transfer from excited photosensitizer to C1, is the active species of CO2 conversion. No synergistic effect of two cobalt centers exists for CO2 reduction because of larger Co-Co distance and rigid structure of C1.