PRECISION TUNING OF SINGLE-METAL SITES ON METAL-ORGANIC FRAMEWORKS FOR CATALYSIS AND GAS ADSORPTION

Metal-organic frameworks (MOFs) are a class of porous crystalline materials created by joining metal ions or clusters, known as nodes, with organic linkers to form a continuous structure. Since the chemical and physical properties of MOFs are highly tunable via the judicious choice of metals and organic linkers, and is further expanded by the possibility for post-synthetic modification, MOFs have over the last decade become a powerful platform for the atomically precise tuning of single-metal sites for applications including gas adsorption and separation, heterogenous catalysis, and chemical sensing etc. In this dissertation, the post-modification of MOF nodes via installation of transition metal catalytic sites, as well as the exploration of guest-induced phase changes that alter the chemical properties of node single-metal sites are explored. First, an artificial enzyme mimic on a solid support was synthesized via the post-synthetic insertion of a bis(µ oxo)dicopper moiety between the clusters of a Zr-MOF (i.e., MOF-565) with a short intercluster distance. Like its parent enzyme, the resulting MOF-565-CuII efficiently transfers one oxygen atom from O2 gas to olefins, forming the monooxygenated epoxide products with high activities and selectivities. The effect of node type and saturation on the post-synthetic installation of iron on zirconium MOFs was then studied. The unsaturated, 8-connected Zr6 nodes of MOF-565, as well as the Zr9 nodes of another new MOF, NPF-520, were furnished with iron(III) to afford MOF-565-FeIII and NPF-520-FeIII, respectively. The visible-light photocatalytic oxidation of toluene to benzaldehyde and/or benzoic acid was then used as a benchmark to compare the Zr-Fe catalysts, both of which demonstrated excellent performance and selectivity under mild reaction conditions. Finally, the effect of reversible guest-induced phase changes of a novel flexible cobalt MOF, Co-MOF, on C2 gas adsorption, in particular ethylene, was investigated. Two means for phase-transformation were identified: 1) the guest-assisted rotation of an asymmetric linker affecting the coordination number of Co and 2) the opening and closing of the MOF structure by activation and re-solvation, changing the coordination geometry of Co