Thiophene-Containing Covalent Organic Frameworks for Overall Photocatalytic H2O2 Synthesis in Water and Seawater

H2O2 is a significant chemical widely utilized in the environmental and industrial fields, with growing global demand. Without sacrificial agents, simultaneous photocatalyzed H2O2 synthesis through the oxygen reduction reaction (ORR) and water oxidation reaction (WOR) dual channels from seawater is green and sustainable but still challenging. Herein, two novel thiophene-containing covalent organic frameworks (TD-COF and TT-COF) were first constructed and served as catalysts for H2O2 synthesis via indirect 2e(-) ORR and direct 2e(-) WOR channels. The photocatalytic H2O2 production performance can be regulated by adjusting the N-heterocycle modules (pyridine and triazine) in COFs. Notably, with no sacrificial agents, just using air and water as raw materials, TD-COF exhibited high H2O2 production yields of 4060 & mu;mol h(-1) g(-1) and 3364 & mu;mol h(-1) g(-1) in deionized water and natural seawater, respectively. Further computational mechanism studies revealed that the thiophene was the primary photoreduction unit for ORR, while the benzene ring (linked to the thiophene by the imine bond) was the central photooxidation unit for WOR. The current work exploits thiophene-containing COFs for overall photocatalytic H2O2 synthesis via ORR and WOR dual channels and provides fresh insight into creating innovative catalysts for photocatalyzing H2O2 synthesis.

Automated summary

In this study, two novel thiophene-containing covalent organic frameworks (TD-COF and TT-COF) were used as catalysts for photocatalytic H2O2 synthesis via indirect 2e(-) ORR and direct 2e(-) WOR pathways. The N-heterocycle modules in COFs were found to regulate the photocatalytic performance of H2O2 production. The TD-COF exhibited high H2O2 production yields in deionized water and natural seawater without sacrificial agents. Computational mechanism studies revealed the primary photoreduction unit and central photooxidation unit for ORR and WOR, respectively. This work provides new insights into using thiophene-containing COFs for efficient photocatalytic H2O2 synthesis.