Catalytic Versatility\nof Lead-Free Cu<sup>2+</sup>-Doped Cs<sub>2</sub>AgBiCl<sub>6</sub> Double Perovskite in Sustainable\nPhotocatalysis and Quinazoline Synthesis

In this report, we present a sustainable, all-inorganic,\nlead-free\ndouble perovskite, Cu<sup>2+</sup>-doped Cs<sub>2</sub>AgBiCl<sub>6</sub> (CABC <i>X</i>), designed by using a simple chemical\nreflux approach. This material features an octahedral morphology and\nis explored for the first time as a heterogeneous catalyst in the\nphotocatalytic oxidation of benzyl alcohol to aromatic aldehyde. Benzyl\nalcohol oxidation serves as a model reaction to investigate the impact\nof Cu<sup>2+</sup> doping on Cs<sub>2</sub>AgBiCl<sub>6</sub>, alongside\nthe photocatalytic reduction of nitroaromatics to aniline, unfolding\nits versatility in various catalytic processes. Additionally, the\nCABC <i>X</i> perovskite catalyst has been investigated\nfor the synthesis of several pharmaceutically important quinazoline\nmoieties, yielding excellent results. The catalytic protocols are\nhighly sustainable and applicable to a wide range of substrates of\nrespective catalytic reactions with a high yield of products. Photoluminescence\nstudies reveal that as the molar concentrations of the Cu<sup>2+</sup> dopant increase, the fluorescence intensity of the double perovskite\ndecreases. This trend indicates reduced recombination and better charge\nseparation from <i>X</i> = 0 to <i>X</i> = 30\nmmol % Cu<sup>2+</sup> dopant concentration, contributing to the enhanced\nphotocatalytic activity. Structural and compositional details of the\nsynthesized lead-free perovskite were confirmed through scanning electron\nmicroscopy, transmission electron microscopy, powder X-ray diffraction,\nEDX, and X-ray photoelectron spectroscopy studies, while thermal stability\nwas assessed via thermogravimetric analysis. Our findings demonstrate\nan effective strategy for tuning the photophysical properties of Cs<sub>2</sub>AgBiCl<sub>6</sub> through transition-metal doping, thereby\nexpanding its applications in catalysis.