Inorganic Chemistry, Vol.58, No.23, 15909-15916, 2019
Fixing Flexible Arms of Core-Shared Ligands to Enhance the Stability of Metal-Organic Frameworks
In recent years, more and more research on metal-organic frameworks (MOFs) has focused on exploring their practical applications, where the stability is crucial. Besides the metal-ligand coordination bond, the configuration of the ligand also plays an important role in determining the stability of resulting MOFs. In this work, we demonstrate that fixing flexible arms of core-shared ligands can enhance the stability of their Zr(IV)-MOFs. Two groups, four core-shared tetracarboxylate ligands, 3,3',3 '',3 ''-(pyrene1,3,6,8-tetrayltetrakis(benzene-4,1-diyl))tetraacrylate (PTSA(4-)) and 6,6',6 '',6 ''-(pyrene-1,3,6,8-tetrayl)tetrakis(2-naphthoate) (PTNA(4-)) with the pyrene core and 3,3',3 '',3 '' 1-((9H-carbazole-1,3,6,8-tetrayl)tetrakis(benzene-4,1-diyl))tetraacrylate (CTSA(4-)) and 6,6',6 '',6 ''-(9H-carbazole-1,3,6,8-tetrayOtetrakis-(2-naphthoate) (CTNA(4-)) with the carbazole core are rationally designed. Two ligands in each group have different flexibilities due to the distinct side arms: the styrene arm is flexible, whereas the naphthalene is rigid. Constructed with Zr-6 clusters, four 4,8-connected Zr(IV)-MOFs, Zr6O4(OH)(8)(H2O)(4)(PTSA)(2) (BUT-72) and Zr6O4(OH)(8)(H2O)(4)(PTNA)(2) (BUT-73) with a sqc-a topologic framework structure and Zr6O4(OH)(8)(H2O)(4)(CTSA)(2) (BUT-74) and Zr6O4(OH)(8)(H2O)(4)(CTNA)(2) (BUT-63) with a scu-a structure are obtained, respectively. It is found that the stability of BUT-73 and-63 with the rigid naphthoate-based ligands is significantly enhanced compared with that of BUT-72 and-74 with the flexible phenyl acrylate-based ones. Moreover, stable BUT-63 represents outstanding performance in the molecular recognition of most solvents commonly used in organic synthesis and industrial manufacture.