Robust Nitro-Functionalized {Zn₃}-Organic Framework for Excellent Catalytic Performance on Cycloaddition Reaction of CO₂ with Epoxides and Knoevenagel Condensation

Adjusting the Lewis acid–base sites in MOF-based catalysts to meet the demand for catalytic CO2 chemical fixation is a huge challenge. Herein, a highly robust rectilinear {Zn3}-based metal–organic framework of {[Zn3(TNTNB)2(4,4′-bip)(H2O)2]·5DMF·9H2O}n (NUC-80) was generalized from the solvothermal condition (H3TNTNB = 1,3,5-tri(3-nitro-4-carboxyphenyl)-2,4,6-trinitrobenzene, 4,4′-bip = 4,4′-bipyridine). Activated NUC-80a not only owns the large void volume (58%) and two kinds of solvent-accessible channels: rhombic-like (ca. 14.24 × 14.57 Å) along a axis and rectangular-like (ca. 11.72 × 14.48 Å) along b axis, but also is functionalized by rich metal sites and plentiful nitro groups on its inner surface. Performed catalytic experiments confirmed that NUC-80a could efficiently catalyze the cycloaddition reaction of CO2 with epoxides and Knoevenagel condensations of aldehydes and malononitrile under mild conditions with a high turnover frequency (TOF). Hence, this work provides a nitro-functionalized metal cluster-based nanoporous metal–organic framework with a wide range of potential applications such as catalysis, gas adsorption, and separation.