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.