Ligand-Directed Dimensionality Control over Zr-Based Metal–Organic Materials: From an Extended Framework to a Discrete Metal–Organic Cage and Macrocycle

Abstract

Different from extensively documented zirconium-cluster-based frameworks, discrete molecular assemblies based on zirconium hexanuclear clusters have scarcely been reported, mainly due to the lack of control over the connectivity of clusters. In this work, we propose a new strategy for controlling the highly connected Zr clusters and report two unprecedented discrete Zr-based metal–organic systems, a {Zr72} metal–organic cage (IAM-5) based on Zr12 clusters and a {Zr24} metal–organic macrocycle (IAM-6) based on Zr6 clusters. Structural analyses reveal that the combination of a unique bowl-shaped geometry, deliberately controlled bridging angles, and conformational flexibility brings a characteristic coordination geometry to the ligand, with significant effects and controls on the connectivities of Zr clusters as low as 4 for Zr12 nodes in IAM-5 and 2 for Zr6 nodes in IAM-6, consequently directing the formation of discrete rather than extended structures.

Zr- and Ti-based metal–organic frameworks: synthesis, structures and catalytic applications

“…65 Thus, Zhao and co-workers reported some interesting results, including 2D nets, a two-fold interpenetrated ftw structure, (4,10)-connected and (4,8)-connected sqc nets and discrete metal–organic cage and macrocycle. 66–69 Surprisingly, Gascon synthesized two new 2D Zr-MOFs based on tetrathiafulvalene linkers with sql topology. 70 Thus, PCN-903-(CH 3 ) 6 was also constructed by our group with (4,6)-connected cor topology, in which the tetracarboxylate linkers with C 1 symmetry bridged the Zr 6 clusters with different dihedral angles.…”