Carbonylation catalysis of aryl halides through active-site engineering

Crystalline palladium phosphide nanoparticles supported on silica (Pd$_3$P/SiO$_2$, 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 Pd$_3$P 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 Pd$_3$P/SiO$_2$ 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.