Green and Reusable Ni@AC-IL-Al2O3 Nanocatalyst for Efficient A3 Coupling, Nitroarenes Reduction, Zeta Potential Analysis, and Selective Adsorption of Cationic Dyes

Abstract A major challenge in sustainable heterogeneous catalysis is the effective utilization of low-cost waste resources without compromising catalytic activity, stability, and recyclability. Herein, we report the rational development of a biomass-derived hierarchical nanocatalyst, Ni@AC-IL-Al2O3, synthesized via ionic-liquid-mediated functionalization of peanut shell-derived activated carbon (AC), followed by integration with aluminum foil waste-derived Al2O3 and subsequent immobilization of uniformly dispersed Ni nanoparticles. The synergistic interplay between the high surface area carbon matrix, ionic-liquid-engineered surface chemistry, and mechanically robust Al2O3 framework promotes strong metal-support interactions and efficient dispersion of Ni active sites. The synthesized catalyst was comprehensively characterized using BET, TGA, XPS, HRTEM, FESEM, and related techniques to elucidate its structural, morphological, and surface properties, which are known to critically influence catalytic behavior in heterogeneous systems. This engineered architecture exhibits excellent catalytic performance in A3 coupling and nitroarene reduction under mild conditions, achieving high conversion (95%) with remarkable selectivity. Electrokinetic studies, including zeta potential analysis, confirm that ionic liquid functionalization enhances surface charge stabilization, leading to improved colloidal stability and catalytic efficiency. In addition to its catalytic activity, the nanocatalyst demonstrates efficient adsorption of Rhodamine B (RhB) and other cationic dyes, attributed to synergistic electrostatic interactions, π–π stacking, H-bonding, and abundant surface-active sites. The catalyst also displayed outstanding operational durability, with negligible Ni leaching and retention of over 90% catalytic activity after five consecutive cycles.