Ethynyl‐Linked Donor–Acceptor Covalent Organic Framework for Highly Efficient Photocatalytic H2O2 Production

Abstract

Photocatalytic H2O2 synthesis from H2O and O2 is considered to be one of the most promising alternative approaches for manufacturing H2O2. Developing highly active and selective photocatalysts is of significant in achieving efficient H2O2 photosynthesis. Herein, an ethynyl‐linked donor–acceptor covalent organic framework (COF), named EBBT‐COF, is prepared from the condensation reaction between an electron‐deficient unit 4,4′,4″‐(1,3,5‐benzenetriyltri‐2,1‐ethynediyl)tris‐benzenamine and an electron‐rich unit benzo[1,2‐b:3,4‐b′:5,6‐b″]trithiophene‐2,5,8‐tricarboxaldehyde. Powder X‐ray diffraction and N2 adsorption isotherm unveil the crystalline porous hcb network of EBBT‐COF with pores size centered at ca. 2.3 nm. Spectroscopic characterizations demonstrate the excellent visible‐light absorption capacity and enhanced photo‐induced charge separation and transport efficiency of EBBT‐COF owing to its donor–acceptor architecture. Density functional theory calculations and electrochemical tests indicate the high activity and selectivity of EBBT‐COF toward 2e− O2 reduction reaction and 2e− water oxidation reaction with triethynylbenzene and trithiophene moieties to accelerate O2‐to‐H2O2 and H2O‐to‐H2O2 conversion, respectively. These merits enable EBBT‐COF to be a promising photocatalyst toward H2O2 generation from H2O and O2 with a H2O2 yield rate of 5 686 µmol g−1 h−1, an optimal apparent quantum yield of 15.14%, a solar‐to‐chemical conversion efficiency of 1.17% (λ > 400 nm), representing one of the best performance among COF‐based photocatalysts reported thus far.