Hot π-electron Tunneling of Metal-Insulator-COF Nanostructures for Efficient Hydrogen Production.

A novel metal-insulator-semiconductor (MIS) photosystem based on covalent organic frameworks (COFs) semiconductors was designed smartly to allow for robust and efficient hydrogen evolution under visible light irradiation. A maximal H 2 evolution rate of 8.42 mmol h -1 •g -1 and an impressive turnover frequency of 789.5 h -1 were achieved in such an organic MIS photosystem prepared by the electrostatic self-assembly of polyvinylpyrrolidone (PVP) insulator-capped Pt nanoparticles (NPs) with the hydrophilic imine-linked TP-COFs with the =C=O-H-N= hydrogen-bonding groups. The hot π-electrons in the photoexcited n-type TP-COF semiconductors can be efficiently extracted and tunneled to Pt NPs across an ultrathin PVP insulating layer to reduce protons to H 2 . Compared to the Schottky-type counterparts, the COF-based MIS photosystems give a 32-fold-enhanced carrier efficiency, attributed to the combined enhancement of photoexcitation rate, charge separation and oxidation rate of holes accumulated in valence band of the TP-COF semiconductor.

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