Polyoxometalates (POMs) are known for their photocatalytic hydrogen production activity, but their solubility and limited stability often restrict their practical applications. Herein, we designed and solvothermally synthesized two new Cu–H2bpz (3,3′,5,5′-tetra­methyl-4,4′-bipyrazole, abbreviated as H2bpz) compounds, namely, Cu0.5(H2bpz)­(NO3) (1) and Cu­(Hbpz)­(Cl)·DMF (2), and three new polyoxometalate-based Cu­(II)-pyrazolate compounds, namely, Cu­(PW12O40)0.5(H2bpz)2(H2O)·(OH)0.5(H2O)5.5 (3), Cu­(HPMo12O40)­(H2bpz)2(H2O)2·(H2O)4 (4), and Cu2(SiW12O40)­(H2bpz)3(H2O)3·(H2O)6 (5). Compound 3 (Cu­(PW12O40)0.5(H2bpz)2(H2O)·(OH)0.5(H2O)5.5) exhibits the best photocatalytic activity of 44.4 μ L h–1 g–1, which may be related to the stability of compounds. Herein, the solvothermal method has been proven to be an effective method in synthesizing stable organic–inorganic hybrid compounds with soluble POMs, metal ions, and organic ligands. Thus, heterogeneous catalysts with outstanding solar-light-driven photocatalytic properties were obtained.

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Perovskite solar cells (PSCs) are one of the most prominent photovoltaic technologies, yet their stability, scalability, and engineering at the molecular level remain challenging. Herein, we report a facile strategy that can simultaneously enhance the stability and efficiency of perovskite optoelectronic devices. In particular, we introduce a passivation molecule, cyclohexylethylamine (CHEA), whose amine group can effectively reduce the number of defect sites and improve the crystallinity of the perovskite by forming Lewis adducts with undercoordinated Pb 2+ ions in the perovskite. Upon passivation by CHEA, the stability and performance of PSCs are correspondingly improved. By optimizing the concentration of CHEA, the power conversion efficiency of the device has been significantly improved from 18.05 to 21.53%.