Synergistic tuning of the phase structure of alumina in supported palladium catalyst for enhanced Suzuki-Miyaura coupling reaction

Abstract

Suzuki coupling reactions are widely employed in natural product synthesis due to their high efficiency and selectivity in constructing target molecules. The development of heterogeneous palladium-based catalysts and sustainable ligand-free catalytic systems remains a key focus in Suzuki coupling research, aiming to minimize environmental impact, enhance resource utilization, and advance the sustainability of chemical processes. In this study, Al₂O₃ precursors were synthesized via electrospinning, followed by calcination at varying temperatures to produce different crystalline forms of Al₂O₃. Pd/Al₂O₃-x catalysts were then prepared using an impregnation method. The structural properties of the synthesized catalysts were systematically characterized using SEM, TEM, XRD, XPS, BET, and FTIR. The results demonstrate that the catalysts exhibit a fibrous tubular morphology with uniform Pd dispersion, thereby increasing the number of active Pd nanoparticles. Notably, γ-Al₂O₃ exhibited stronger interactions with Pd compared to the other crystalline forms. The resulting material demonstrated exceptional catalytic performance in Suzuki coupling reactions, achieving a high turnover frequency (TOF = 3186.1 h^-1). The effects of reaction temperature, time, solvent, and base on catalytic efficiency were systematically investigated in this work. Moreover, the catalyst maintained stable activity over five reaction cycles, highlighting its excellent recyclability and reusability.