Covalent organic frameworks for direct photosynthesis of hydrogen peroxide from water, air and sunlight.

Solar-driven photosynthesis is a sustainable process for the production of hydrogen peroxide, the efficiency of which is plagued by side reactions. Metal-free covalent organic frameworks (COFs) that can form suitable intermediates and inhibit side reactions show great promise to photo-synthesize H 2 O 2 . However, the insufficient formation and separation/transfer of photogenerated charges in such materials restricts the efficiency of H 2 O 2 production. Herein, we provide a strategy for the design of donor-acceptor COFs to greatly boost H 2 O 2 photosynthesis. We demonstrate that the optimal intramolecular polarity of COFs, achieved by using suitable amounts of phenyl groups as electron donors, can maximize the free charge generation, which leads to high H 2 O 2 yield rates (605 μmol g -1 h -1 ) from water, oxygen and visible light without sacrificial agents. Combining in-situ characterization with computational calculations, we describe how the triazine N-sites with optimal N 2p states play a crucial role in H 2 O activation and selective oxidation into H 2 O 2 . We further experimentally demonstrate that H 2 O 2 can be efficiently produced in tap, river or sea water with natural sunlight and air for water decontamination.