Covalent metal-organic frameworks for cocatalyst-free <?A3B2 pi6?>photo-catalytic hydrogen production

Development of novel metal-organic framework (MOF) based photocatalysts for highly efficient hydrogen production from water or even seawater in the absence of noble metal as cocatalysts or photosensitizers, is highly demand yet remains a significant challenge. Herein, we have synthesized four MOFs, namely n-OH-JNM (n = 0, 1, 2, and 3), composed of copper-based cyclic trinuclear units (Cu-CTUs) and organic linkers with different numbers of –OH groups. By regulating the number of –OH groups, the optical properties, including light adsorption ability, band gap and charge separation efficiency, can be modulated, resulting in the dramatic improvement of photocatalytic hydrogen production rate. Specifically, in the absence of co-catalysts, 2-OH-JNM can achieve a high hydrogen production rate of 4.07 and 1.49 mmol g−1 h−1 in pure water and natural seawater, respectively, while the other three JNMs cannot produce hydrogen under the same conditions. To the best of our knowledge, 2-OH-JNM is currently the most efficient MOF-based photocatalyst in pure water for hydrogen production without any co-catalyst. Our work provides a new strategy for the development of noble-metal-free and co-catalyst-free MOF photocatalysts.