Sodium Alginate–CdS Nanostructures: Reinforcing Chemoselectivity in Nitro-Organic Reduction and Dye Degradation through Photoinduced Electron Transfer

In the current socioeconomic environment, researchers are interested in using visible light for the exploration of chemical reactions. In this context, biopolymer-supported multifunctional metal sulfide composites with improved catalytic performance play a crucial role in chemical reactions. To address this issue, sodium alginate-templated cadmium sulfide-based photocatalysts are synthesized at a gel–liquid interface by altering the pH of the Na2S solution from 7.4 to 10 and 13. The X-ray diffractograms (XRDs) of the synthesized sodium alginate–cadmium sulfide (SA–CdS) illustrated the semicrystalline nature of the cadmium nanostructures. Field emission scanning electron microscopy (FE-SEM) is used to examine the surface morphology of the nanocomposites. The transmission electron microscopy (TEM) analysis reveals that the sodium alginate–cadmium sulfide (SA–CdS) particles exhibit spherical shapes with an average size of 4 nm. The diffuse reflectance spectroscopy (DRS) and Brunauer–Emmett–Teller (BET) analysis reveal the low band gap (∼2.4 eV) and enhanced surface area for SA–CdS synthesized at pH 13 of Na2S solution compared to pH 10 and 7.4, respectively. In contrast to the reported photocatalysts, the synthesized SA–CdS not only reduced the nitro-organic compounds under incoming irradiation but also reduced the chemoselectively deteriorated nitro compounds having vinyl functional groups. Additionally, the SA–CdS photocatalyst efficiently degraded organic rhodamine B (RhB) dye under visible light irradiation. Additionally, the essential function of electrons in reducing nitroaryl compounds is revealed, and a potential photocatalytic reaction mechanism using ammonium formate as a hole scavenger is also proposed. The synthesized SA–CdS catalyst demonstrates remarkable recyclability without any noticeable decrease in the amount of product obtained. These findings suggest that the developed SA–CdS catalyst has the potential to serve as a promising visible-light-driven photocatalyst for various organic reactions.