The One-pot Encapsulation of Palladium Complexes into Covalent Organic Frameworks Enables the Alkoxycarbonylation of Olefins

In this study, palladium-based heterogeneous catalysts were successfully prepared by encapsulating the palladium diphosphine complexes into an imine-linked 2D-COF (TPB-DMTP-COF) through a one pot self-assembly approach. It not only prevents the oxidation of phosphine-based ligand during the stepwise impregnation but also suppresses the coordination of imine linkers at the COF host to the palladium guest, thus enabling highly efficient encapsulation of the active bidentate phosphine chelated palladium complex by the widely explored imine-linked COF. Besides, the dosage of diphosphine ligand (Xantphos-SO₃H, L) and the ratio of palladium to L in the preparation of [Pd]@COF hybrids can be readily adjusted under such one pot procedure to satisfy the requirement of crystallinity, porosity, active sites, and CO adsorption capacity for the catalytic performance in the methoxycarbonylation of olefins. The resultant [Pd]@COF-A-0.25-0.5 provides satisfied catalytic performance for both aliphatic and aromatic olefins with total esters up to 92.1 % under optimized conditions. These findings provide the basis for a novel design concept to design heterogeneous catalysts with high efficiency for reaction processes comprising the alkoxycarbonylation of olefins.