Carbonylation catalysis of aryl halides through active-site engineering

Crystalline palladium phosphide nanoparticles supported on silica (Pd3P/SiO2, 5 wt% Pd) are explored as catalysts for the alkoxycarbonylation of lignin-derived aromatic synthons, using model aryl halides as representative substrates. The detailed characterization by PXRD, HAADF-STEM, HRTEM, EDX, ICP-AES, XPS, CO-DRIFTS, and CO chemisorption confirmed the formation of the Pd3P phase with uniform nanoparticle size distribution. The catalytic performance was evaluated in a three-phase reaction system comprising a CO gas atmosphere, a liquid phase containing the solvent and substrate and a solid catalyst. The incorporation of phosphorus into the palladium lattice resulted in a more than two-fold enhancement in catalytic activity compared to conventional Pd-based heterogeneous catalysts. The Pd3P/SiO2 catalyst also outperformed several reported heterogeneous and commonly used homogeneous catalysts. This enhanced reactivity is attributed to the electronic and geometric effects introduced by phosphorus, which generate highly active, spatially-isolated Pd sites. These findings demonstrate the potential of Pd–P phase engineering for the design of the next-generation of carbonylation catalysts.