Single-Crystal Synthesis and Diverse Topologies of Hexanuclear CeIV-Based Metal-Organic Frameworks

Ce-6(IV)-based metal-organic frameworks (MOFs) have gained increasing attention recently because of their diverse potential applications and similarity to prominent Zr-MOFs, e.g., the UiO-66 series. However, the reported Ce-6(IV)-based MOFs were all structurally determined by means of the powder X-ray diffraction technique, indicative of less practice and convenience. Herein, four single-crystalline Ce-6(IV)-based MOFs were successfully isolated and characterized by single-crystal X-ray diffraction, disclosing two series of topologically distinct isoreticular nets accompanied by nine-coordinated central Ce-IV ions, i.e., 8-connected hex and 12-connected fcu, respectively, in contrast to the previously reported sole fcu topology based on the combination of linear dicarboxylate ligands and a Ce-6(IV)-cluster associated with eight-coordinated central Ce-IV ions according to the UiO-66 structural model. Moreover, all four single-crystalline compounds exhibit permanent microporous porosities and a certain amount of gas uptake toward CO2, CH4, and H-2.