Thiophene-Containing Covalent Organic Frameworks for Overall Photocatalytic H O Synthesis in Water and Seawater.

H O is a significant chemical widely utilized in the environmental and industrial fields, with growing global demand. Without sacrificial agents, simultaneous photocatalyzed H O 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 H O synthesis via indirect 2e ORR and direct 2e WOR channels. The photocatalytic H O 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 H O production yields of 4060 μmol h  g and 3364 μmol h  g 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 H O synthesis via ORR and WOR dual channels and provides fresh insight into creating innovative catalysts for photocatalyzing H O synthesis.