Modulated Multicomponent Reaction Pathway by Pore-Confinement Effect in MOFs for Highly Efficient Catalysis of Low-Concentration CO2

Abstract

The conversion of flue gas CO₂ into high-value chemicals via multicomponent reactions (MCRs) offers the advantages of atom economy, bond-formation efficiency and product complexity. However, because of the competition between reaction sequences and pathways among substrates, the efficient synthesize the desired product is a great challenge. Herein, a porous noble-metal-free framework (Cu-TCA) was synthesized, which can highly effectively catalyze the multicomponent conversion of CO₂ by modulating reaction pathways. The pores with the size of 6.5 Å×6.5 Å in Cu-TCA selectively permit the entry of propargylamine and CO₂ at simulated flue gas concentrations, At the same time, the larger-sized phosphine oxide is hindered outside the pores. Control experiments and NMR spectroscopy revealed that CO₂ and propargylamine in the pores preferentially reacted to form oxazolidinones, which further reacted with phosphine oxide outside the pores to produce phosphorylated 2-oxazolidinones. Therefore, the reaction pathways and sequence of the substrates were controlled by the confinement effect of the pores in Cu-TCA. Density functional theory (DFT) calculations supported the coordination of Cu-TCA with the alkyne, significantly reducing the reaction barrier and promoting catalytic reaction. This study developed a new strategy for regulating the reaction pathways to promote MCRs via the confinement effect of MOF.