A covalent organic framework inspired by C3N4 for photosynthesis of hydrogen peroxide with high quantum efficiency

Abstract

Carbon nitride (C3N4) has been the main research focus for photocatalytic H2O2 synthesis that may enable the on-site and on-demand H2O2 production under mild conditions. Its potential is unfortunately shadowed by the narrow light absorption and fast charge recombination. Building on the understanding of the inherent merits and pitfalls of C3N4, we here propose to assemble active heptazine motifs with functional linkers in ordered molecular frameworks for highly efficient photocatalytic H2O2 production. Herein, a heptazine-based covalent organic framework is synthesized via the Schiff-base reaction. It has enhanced light absorption and charge separation. When irradiated with visible light in the presence of sacrificial electron donors, the sample exhibits an excellent H2O2 production rate of 11986 μmol h–1 g–1 and an apparent quantum efficiency up to 38% at 420 nm, outperforming most organic or inorganic competitors in our best knowledge. Impressively, the catalyst can also endure long time operation that affords the linear H2O2 accumulation to a practically usable concentration.