Molecular size- and shape-selective Knoevenagel condensation over microporous Cu3(BTC)2 immobilized amino-functionalized basic ionic liquid catalyst

• Amino-functionalized basic ionic liquid was confined in Cu3(BTC)2 nanocavities.
• Confined microenvironment with microporous window was constructed.
• Synthesized catalyst showed excellent catalytic performance and reusability.
• Size- and shape-selective catalysis in Knoevenagel condensation was observed.
• Diffusion kinetics of reactants might be the controlling step.

A novel molecular size- and shape-selective catalyst, microporous metal-organic framework HKUST-1 immobilized amino-functionalized basic ionic liquid (ABIL-OH), was synthesized by facile impregnation and activation. Characterizations and catalytic results revealed that the catalytically active species ABIL-OH could be confined in well-defined HKUST-1 nanocavities via CuNH2 coordination bond. The resulting ABIL-OH/HKUST-1 heterogeneous catalyst showed comparable catalytic activity and enhanced selectivity in liquid phase Knoevenagel condensation, and it could be recovered conveniently and reused at least 5 times without significant loss of its catalytic efficiency. Moreover, ABIL-OH/HKUST-1 catalyst demonstrated distinct size- and shape-selective properties for discrimination of reactants in Knoevenagel condensation. It was supposed that diffusion kinetics of reactants might be controlling step and play a more important role than the nature of the substituents in the confined microenvironment.

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