Organic terpyridine molecule as an efficient cocatalyst for metal–free CO2 photoreduction mediated by mesoporous graphitic carbon nitride

Abstract

Metal-free catalytic conversion of CO2 with high selectivity and efficiency is promising for achieving carbon neutrality. However, nonmetallic catalytic sites for highly selective and efficient CO2 photoconversion are still challenging. In this work, organic terpyridine molecules are developed as highly active cocatalysts for visible-light-driven CO2 reduction with a CO evolution rate of 1.92 × 104 μmol g−1h−1 and 99.8% selectivity in aqueous solution, which is among the highest CO evolution rates for metal-free CO2 photoreduction. Mechanistic studies revealed that efficient electron transfer from organic light-absorbing photosensitizer to terpyridine molecules was mediated by mesoporous g-C3N4 (mpg-C3N4), with no need of much efforts to optimize inherent fast charge recombination of pristine mpg-C3N4. The synergistic effect of mpg-C3N4 and terpyridine molecule suppressed H2 evolution process from CB of mpg-C3N4 and promoted CO2 reduction at terpyridine sites. These results pave a feasible way to achieve robust metal-free CO2 photoreduction by employing organic molecular hybrid photocatalysis.