Embedding [Mo3S13]2− clusters into the micropores of a covalent organic framework for enhanced stability and photocatalytic hydrogen evolution

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Non-noble-metal-based [Mo3S13]2− nanoclusters (MS-c) as a co-catalyst face the problems of instability and inevitable aggregation, which limit its photocatalytic applications. Herein, β-ketoenamine-linked covalent organic framework (COF), namely TpPa-1-COF, was utilized to embed MS-c. The micropores of TpPa-1-COF could not only limit the growth of MS-c to achieve its high dispersion but also play a central role in anchoring MS-c. Moreover, the structural stability of MS-c is highly enhanced due to the confinement effect of TpPa-1-COF, and the visible-light-driven photocatalytic H2 evolution rate of 528 μmol g−1h−1 for MS-c@TpPa-1 (0.3: 1), which is increased by 4.7 times as compared with that of TpPa-1-COF. The density functional theory (DFT) calculations indicate that the electrons transfer from TpPa-1 to MS-c occurs at the interface of MS-c@TpPa-1 in the ground state based on the charge density difference analysis. With the irradiation of visible light, the photoexcited electrons derived from the π-conjugated TpPa-1-COF backbone could be delivered to the embedding MS-c through the coordinated Mo − N groups, and the favorable electron–proton transfer to form H* and efficient desorption of H2 occurs on the S sites instead of N sites in MS-c@TpPa-1, resulting in the enhanced photocatalytic H2 evolution rate. Overall, this work provides a novel approach for embedding the unstable MS-c with low cost into the micropores of COF via coordination bonds to improve the structural stability and photocatalytic activity.