Benzotrithiophene-based covalent organic frameworks as efficient catalysts for artificial photosynthesis of H₂O₂ in pure water

Direct synthesis of hydrogen peroxide (H2O2) using oxygen and water through the photocatalytic route is a prospective approach for the on-site production of H2O2. However, the limited varieties of photocatalytic sites and ambiguous structure-active relationship impede the development of environmentally friendly technology. Herein, we report a active compound (benzotrithiophene, BTT) for the photosynthesis of H2O2 using oxygen and water, and design four benzotrithiophene-based 2D covalent organic frameworks (BTT-COFs) linked with aromatic amines linkers. Significant enhancement in photocatalytic activity has been observed via the introduction of BTT struct into 2D COFs. The high crystallinity of COFs increases the visible light absorption ability and photostability of BTT. The suitable distance of BTT struct in COFs and the construction of donor-acceptor (D-A) structure further promote the carrier generation and transfer. The COF-BTT-TAPT exhibited the highest H2O2 production rate of 620 mu mol g-1 h-1. Mechanism investigation experiments have given the validation that BTTCOFs efficiently reduce oxygen in pure water to form H2O2 under visible-light irradiation. This work paves a revolutionary way for designing and fabricating high-performance metal-free photocatalysts for visible-lightdriven H2O2 production.