Nanocage-based {In2Tm2}-organic framework for efficiently catalyzing the cycloaddition reaction of CO2 with epoxides and Knoevenagel condensation

High density active sites and chemical stability for prepared MOFs are the prerequisites for their industrial applications, which prompted us to synthesize cluster-based metal-organic compounds. The combination of [In2Tm2(mu(2)-OH)(2)(CO2)(10)(H2O)(2)] clusters ({In2Tm2}) and the functional ligand 2,6-bis(2,4-dicarboxylphenyl)-4-(4-carboxylphenyl)pyridine (H5BDCP) produced an extremely stable nanoporous skeleton of {(Me2NH2)(2)[In2Tm2(BDCP)(2)(mu(2)-OH)(2)(H2O)(2)]center dot 2DMF center dot 3H(2)O}(n) (NUC-56), whose inner surface is functionalized by Lewis acidic and basic groups of metal centers, mu(2)-OH groups and N-pyridine atoms. To the best of our knowledge, NUC-56 is a rarely reported planar-cluster-based {In(2)Ln(2)}-organic framework, which possesses an excellent confined pore environment with high porosity, large specific surface area and abundant co-existing Lewis acid and base sites. Consequently, NUC-56a exhibited a good catalytic performance for the cycloaddition reaction of various epoxides with CO2 and the Knoevenagel condensation reaction of different aldehydes and malononitrile under mild conditions. Therefore, this study can provide some guidance for the precise design of practical MOFs with excellent catalytic, stability and regeneration performances through the participation of rare earth ions.