Modulating Catalytic Selectivity via NiZn-CdS Interface for Visible-Light Mediated Suzuki Cross-Coupling and Standalone NiZn Alloy for Ambient Synthesis of 1,2,3-Triazoles.

Abstract

We report the synthesis of cost-effective, noble metal- and copper-free NiZn alloy, CdS QDs, and their hybrid NiZn-CdS nanocomposite and compared their efficiency as heterogeneous catalysts for visible light-mediated Suzuki-Miyaura cross-coupling (SMCC) and regioselective azide-alkyne cycloaddition (AAC) reactions. A key breakthrough of this study is the catalytic inefficiency of hierarchically arranged NiZn alloy alone for the SMCC reaction, under visible light illumination. However, upon integrating CdS QDs onto NiZn alloy nanoparticles via nanoscale-interfacial engineering, we observe a remarkable catalytic enhancement. The newly developed NiZn-CdS composite exhibits unprecedented photocatalytic efficiency under visible-light for the SMCC reaction. In contrast, for the AAC reaction, where azides were formed in-situ, the composite demonstrates no catalytic activity under visible light. Interestingly, when CdS QDs are decoupled, the NiZn alloy alone shows outstanding catalytic performance for the regioselective formation of 1,4-disubstituted 1,2,3-triazoles at room-temperature. This represents the first report of a room-temperature, copper-free catalytic system without the use of any noble metal, that outperforms many previously reported copper-free catalysts for AAC, both in terms of activity and selectivity. Further, the sustainability matrices of the developed catalytic protocols were determined through comprehensive green chemistry assessments which demonstrate the protocol's environmental friendliness and adherence to green chemistry principles.