A simple terpyridine-cobalt(II) complex sensitized by connective mpg-C₃N₄ for improved CO₂ photoreduction

A noble metal-free hybrid photocatalysts (Cotpy@mpg-C3N4) composed of mesoporous carbon nitride (mpg-C3N4) and a simple molecular terpyridine-Co(II) complex (Co(ptpy)Cl2) has been synthesized for CO2 photoreduction. The hybrid photocatalyst exhibited high and durable CO formation (3.41 x 104 mu mol g-1) after 48 h of visible light irradiation, which is much better than corresponding separated system without a covalent connection. The introduction of Co(ptpy)Cl2 to mpg-C3N4 via a covalent amido bond in Cotpy@mpg-C3N4 improved the reducing ability of conduction bond (-1.58 V vs. SCE) and CO2 adsorption capacity (3.23 mmol g-1). Further mechanistic studies revealed that the efficient cooperation between light-absorbing mpg-C3N4 and catalytic site Co(ptpy)Cl2 was crucial and facilitated electron transfer and charge separation during photocatalysis. This work highlights the synergistic effect of constituent components in the hybrid photocatalyst for CO2 photoreduction.