Clay Mineral-Derived\nSilica Nanosheets as a Sustainable\nPlatform for Photochemical Synthesis of Supported Metal Catalysts

Clay minerals and their derivatives are valued for their\nunique,\nlow-dimensional nanostructures. It is imperative to explore the characteristics\nof nanoclay-based matrix materials for the green synthesis of functional\ncomposites. This study reveals the defect-induced semiconductor-like\noptical properties of kaolinite clay-derived silica nanosheets (SiNSs)\nand employs SiNSs as a sustainable support and photoinduced reducing\nagent for the photochemical synthesis of supported metal nanoparticles\n(NPs). Results show that SiNSs feature defects that show UV absorption\nability, a band gap of 2.99 eV, and higher photogenerated carrier\nseparation efficiency than kaolinite and fumed nanosilica. Consequently,\nthe photoexcited electrons of SiNSs under UV irradiation efficiently\nreduce Ag/Cu-amine precursors to produce SiNS-supported Ag-only and\nAgCu-alloy NPs. Furthermore, the impact of UV intensity on the Ag/Cu\nratio and composition of alloy NPs due to the metal–support\ninteraction and alloying effect is clarified. The optimal AgCu/SiNS-5\ncomposite consisting of Ag<sub>0.35</sub>Cu<sub>0.65</sub> alloy NPs\n(∼12 nm) exhibits superior catalytic activity for <i>p</i>-nitrophenol reduction within 40 s with a turnover frequency of 4.36\nmin<sup>–1</sup> owing to high adsorption and reactivity of\nthe interfacial and alloying active sites, and multiple electron transport\npathways enabled by the alloying effect of Ag<sup>0</sup>/Cu<sup>+</sup>/Cu<sup>0</sup>/(AgCu)<sup>0</sup>. This work indicates the great\npotential of clay-derived SiNS’s optical properties in photochemical\nsynthesis of supported metal catalysts, emphasizing the key roles\nof metal–support interaction and alloying effect in synthesis\nand catalysis.