Rational design of lead-free CsCu2I3@g-C3N4 composite for efficient energy storage and sustainable catalysis†

Rationally constructed lead-free halide perovskite-based composites provide an effective approach for upgrading their many unique physicochemical properties. In this study, we report the design and synthesis of a stable lead-free CsCu₂I₃ (CCI) perovskite integrated with g-C₃N₄ (CN) using a simple ultrasonication approach. The individual components, CsCu₂I₃ and g-C₃N₄, were synthesized separately using the hot-injection method and the thermal polycondensation method, respectively. Interestingly, the composite material CsCu₂I₃@g-C₃N₄ (CCI–CN) exhibited outstanding hybrid supercapacitive behaviour and opened a new avenue for the untapped electrochemical potential of Cu-based lead-free halide perovskites. The hybrid CCI–CN material was also examined, for the first time, as a heterogeneous multifunctional catalyst in the photo-hydration of benzonitrile and the photo-reduction of para-nitroaniline. Moreover, the synthesized composite catalyst was very efficient in the synthesis of the medicinally potent N-heterocyclic compounds, quinazolin-4(3H)-one moieties. It was observed that CsCu₂I₃@g-C₃N₄ not only outperformed its individual components, CsCu₂I₃ and g-C₃N₄, but also surpassed other reported catalysts in the aforementioned transformations, delivering excellent product yields. This was attributed to the cooperative and synergistic effects of the CsCu₂I₃ and g-C₃N₄ heterojunction. Photoluminescence studies revealed that the reduced recombination in the composite material provided a fast channel for the transfer of photo-generated electrons, with the lower PL lifetime of CCI–CN (119.8307 ns) compared to CCI (151.2798 ns). Hence, this study provides ideas and opportunities of Cu-based halide perovskite composites as efficient materials for charge storage and versatile catalytic activity.