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

Abstract

Adjusting the Lewis acid−base sites in MOF-based catalysts to meet the demand for catalytic CO 2 chemical fixation is a huge challenge. Herein, a highly robust rectilinear {Zn 3 }-based metal−organic framework of {[Zn 3 (TNTNB) 2 (4,4′-bip)(H 2 O) 2 ]• 5DMF•9H 2 O} n (NUC-80) was generalized from the solvothermal condition (H 3 TNTNB = 1,3,5-tri(3-nitro-4-carboxyphenyl)-2,4,6trinitrobenzene, 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 CO 2 with epoxides and Knoevenagel condensations of aldehydes and malononitrile under mild conditions with a high turnover frequency (TOF). Hence, this work provides a nitrofunctionalized metal cluster-based nanoporous metal−organic framework with a wide range of potential applications such as catalysis, gas adsorption, and separation.