Tuning the electronic properties of Zr₆O₈ nodes in the metal organic framework UiO-66 by selection of node-bound ligands and linkers

Wei, R.; Gaggioli, C. A.; Li, G.; Islamoglu, T.; Zhang, Z.; Yu, P.; Farha, O. K.; Cramer, C. J.; Gagliardi, L.; Yang, D.; Gates, B. C.
Chem. Mater. 2019, 31, 1655 (doi:10.1021/acs.chemmater.8b05037).

The metal organic framework (MOF) UiO-66, which incorporates Zr₆O₈ nodes, exhibits high stability under a wide range of conditions that commends it for potential applications. The MOF properties can be tuned by choice of the groups bonded to the node defect sites and to the linkers. We report data for UiO-66 incorporating formate, acetate, benzoate, and trifluoroacetate on the nodes and -NH₂, -OH, -NO₂, and phenyl substituents on the benzene rings of the benzene-1,4-dicarboxylic acid-derived linkers. The MOFs were characterized by infrared and ¹H NMR spectroscopies, thermal gravimetric analysis, N₂ adsorption, X-ray diffraction crystallography, scanning and transmission electron microscopy, and electronic structure calculations. The ligands on the nodes were identified and quantified by ¹H NMR spectra of the MOFs digested in NaOH/D₂O solutions. The effects of the node and linker groups on the electronic properties of the nodes have been quantified with IR spectra of the node μ₃-OH groups and by DFT calculations, which are in good agreement with one another.