Constructing highly reactive Pd nanoparticles with π bonds in imidazolium-based metal–organic frameworks for chemoselective CO2 multicomponent transformation

Abstract

Multicomponent CO₂ conversion to value-added chemicals offers bond-forming efficiency, atom economy, and structural diversity, yet efficient synthesis of desired products is hindered by substrate competition. Herein, a highly selective and efficient Pd nanoparticle (PdNP) catalyst stabilized by π bonds in imidazolium-based-erbium-terephthalate metal–organic frameworks with 13.73 Å × 13.81 Å pores was synthesized in a scalable manner. Optimal 10%Pd@Er-MOF promotes carboxylation–cyclization–cross-coupling tricomponent reactions (4C-TCRs) of propargylic amines, aryl iodides, and in situ-activated CO₂, yielding oxazolidinones (OZDs) with 100% selectivity. The pores of the catalyst permit entry of substrates, and high substrate concentrations around the catalytic center enhance chemoselectivity and efficiency in 4C-TCRs. Control experiments and multiple spectral studies confirm that 10%Pd@Er-MOF enhances CO₂ enrichment and enables in situ generation of free N-heterocyclic carbenes (NHCs), facilitating NHC–CO₂ adduct formation for CO₂ activation, while propargylic amines and CO₂ fail to form OZDs. Density functional theory calculations reveal that 10%Pd@Er-MOF catalyzed 4C-TCRs exhibit a substantially reduced energy barrier versus carboxylative cyclization of propargylic amines and CO₂. The reaction pathway was synergistically controlled by PdNPs, in situ-generated NHCs, and the confinement effect of 10%Pd@Er-MOF. This work reports a new strategy to control reaction pathways for promoting 4C-TCRs via multi-site synergy, enabling CO₂ enrichment/activation and highly selective conversion to target products.