A Ni(salen)‐Based Metal–Organic Framework: Synthesis, Structure, and Catalytic Performance for CO2 Cycloaddition with Epoxides

A three‐dimensional (3D) chiral metal–organic framework [Cd 2 {Ni(salen)}(DMF) 3 ] · 4DMF · 7H 2 O ( 1 ) based on a new enantiopure tetracarboxyl‐functionalized metallosalen Ni(H 4 salen) {where H 6 salen is ( R , R )‐ N , N′ ‐bis[3‐ tert ‐butyl‐5‐(3,5‐dicarboxybenzyl)salicylidene]‐1,2‐diphenylethylenediame} was synthesized and characterized by infrared spectroscopy, thermogravimetric analysis, nitrogen and carbon dioxide adsorption, and powder and single‐crystal X‐ray diffractions. In 1 , the dinuclear Cd 2 cluster [Cd 2 (COO) 4 (DMF) 3 ] as a node is cross‐linked by four isophthalate groups on the salen ligands, forming a 2D lamellar structure, which are further linked by Ni(salen) into the 3D network with a 1D open channel (ca. 7.0 × 8.0 Å 2 ) along the a axis. On account of its porosity, Lewis acid sites, and moderate uptake for CO 2 , 1 can be used as an efficient heterogeneous catalyst for the CO 2 cycloaddition with epoxides under relatively mild conditions. Moreover, the bulky epoxide shows a decrease in activity with an increase in the alkyl chain length of the substrate as a result of the confinement effect of 1 , showing size‐dependent selectivity.