Green-synthesized Nanocatalysts for Organic Reactions: Cross-coupling, Hydrogenation, and Photocatalysis

Abstract: Nanoparticles have attracted considerable interest across multiple disciplines, including medicine, polymers, electronics, and environmental science, due to their distinctive physicochemical properties and diverse applications. Synthesis of nanoparticles can be catego-rized into two principal approaches: top-down and bottom-up. The top-down approach reduces bulk materials to the nanoscale through methods like milling, sputtering, and lithography, while the bottom-up approach assembles nanoparticles from atoms or molecules using techniques such as sol-gel synthesis, CVD, ALD, and hydrothermal methods. Together, they offer versatile routes for nanoparticle fabrication. Each method presents distinct advantages and limitations in terms of particle size control, homogeneity, scalability, and environmental impact. Recent advancements in nanoparticle synthesis have focused on refining these methods to enhance precision, minimize hazardous byproducts, and optimize particle characteristics. Notably, green synthesis strategies, which utilize natural resources such as plant extracts, microorganisms, and biodegradable materi-als, have emerged as environmentally sustainable alternatives for nanoparticle production. These eco-friendly approaches mitigate nanoparticle toxicity, improve biocompatibility, and enhance stability. Nanoparticles play a key role as nanocatalysts in various organic transformations, including Suzuki, Heck, Sonogashira, Negishi, Buchwald-Hartwig amination, Kumada, Murahashi, Fukuyama, Ullmann, Stille, Hiyama, A3, and KA2 coupling reactions. Their application in catalysis is characterized by high sustainability, superior atom economy, low environmental impact (low E-factor), and high turnover number (TON), making them integral to advancing green and efficient synthetic methodologies.