Pyrimidine-Containing Covalent Organic Framework for Photocatalytic Solar Hydrogen Peroxide Production

Photocatalytic production of hydrogen peroxide (H2O2) from water and O2 using organic semiconductor photocatalysts is a promising approach for solar-to-chemical energy conversion. Recently, covalent organic frameworks (COFs) consisting of donor (D)-acceptor (A) conjugates have attracted attention owing to the tunable platforms for semiconductor synthesis. In this study, we synthesized a series of COFs consisting of 2,4,6-triformylphloroglucinol (Tp) as an A unit and different N-containing heterocycles bearing different numbers of terminal -NH2 groups as D units. The COF containing 2,4,6-triaminopyrimidine (PmA3) as the D unit exhibited the highest activity for photocatalytic H2O2 generation. Photoelectrochemical measurements and density functional theory calculations revealed that the high activity of PmA3-COF originates from the high electron conductivity owing to the multibranched triamine structure and high hole-trapping capability of the Pm ring. These properties enhanced oxidation of water by the photogenerated holes, resulting in efficient H2O2 generation.