Photocatalytic H2O2 generation via the two-electron oxygen reduction reaction (2e- ORR) is a highly sustainable approach, capable of proceeding via either a one-step or two-step 2e- ORR route. Nonetheless, precise regulating the 2e- ORR paths still remains a formidable challenge. Herein, for the first time, we modulate the 2e- ORR pathway through unsaturated bond control in covalent organic frameworks (COFs). We synthesize a pair of isostructural COFs distinguished only by their unsaturated bonds. The alkyne-containing TY-COF favors the two-step 2e- ORR route, whereas the alkene-containing TE-COF follows the one-step 2e- ORR route. Without any sacrificial agents in O2, TY-COF and TE-COF display impressive H2O2 production rates of 6455 and 4804 μmol g-1 h-1, respectively. Further theoretical results manifest that the regulation of unsaturated bonds alters the electron-hole distribution along the COFs skeletons, prompting the reorganization of the catalytic centers for ORR (the benzene ring in TY-COF, the triazine in TE-COF), which leads to divergent ORR pathways. Additionally, free-standing TY-COF and TE-COF membranes, via the interfacial polymerization method, are also able to drive the H2O2 photosynthesis. The present work offers a new strategy and valuable inspirations for modulating 2e- ORR pathways via strategic architectural engineering of COFs.
