Triplet Exciton‐Enhanced Photosynthesis of Hydrogen Peroxide Enabled by Topologically Tuned Covalent Organic Frameworks
Can Huang, Youzi Zhang, Rongchen Shen, Lei Hao, Bin Qi, Guijie Liang, Peng Zhang, Xin Li, Xuanhua Li
Abstract
Abstract Artificial photosynthesis technology can utilize water, oxygen, and solar energy to produce hydrogen peroxide (H 2 O 2 ), an environmentally friendly oxidant and a clean fuel. However, H 2 O 2 photosynthesis mainly follows photogenerated electrons/holes pathway, which suffers from high thermodynamic barriers and competing reactions. Triplet excitons can spontaneously convert O 2 into singlet oxygen ( 1 O 2 ) intermediate and bypass these challenges, but demonstrating its effects on photocatalysis is still scarce. Here, this study designs twist pyrimidine‐based covalent organic frameworks with excellent triplet exciton production using a topological tuning strategy. The twist configuration modulates the molecular orbital overlap between singlet and triplet states and achieves a 1.8 × 10 7 enhancement in the intersystem crossing rate, obtaining excitation of triplet excitons and the generation of 1 O 2 , rather than exciting photogenerated electrons and holes. A novel triplet exciton‐ 1 O 2 H 2 O 2 photosynthesis pathway is achieved and demonstrates a 38.6% reduction in the generation barrier compared to typical redox pathway, obtaining record activity with rates of 10.80 mmol g −1 h −1 in an O 2 atmosphere and 7.82 mmol g −1 h −1 in air, without the need for a sacrificial agent. The solar‐to‐chemical conversion efficiency is 1.25%.