(641b) Investigation of Missing-Cluster Defects in UiO-66 and Ferrocene Deposition on Defective Sites for O2/N2 Separation

Due to the high porosity and function diversity of metal-organic frameworks (MOFs), MOFs are recognized as the promising candidates for many adsorptive separation processes, including CO₂/N₂, CO₂/CH₄, and O₂/N₂ separations. Among reported MOFs, UiO-66 is such a special case due to its extraordinary stability. However, the framework inertness limits its potential for many applications. Recently, the investigation of the defects in UiO-66, which significantly increase the activity of framework, have made UiO-66 become much more attractive than ever before. In this presentation, we will discuss the formation of missing-cluster (MC) defects is highly related to the partially-deprotonated ligands. A series of syntheses controlling the defect formation are provided to support the discussion. The number of MC defects are sensitive to the addition of the deprotonation reagent, synthesis temperature, and reactant concentration. Pore size distribution derived from the N₂ adsorption isotherm at 77K allows accurate and convenient characterization of the defects in UiO-66. The existence of defects in UiO-66 framework can cause significant deviations in its pore size distribution from the results derived from the crystal structure file. The generated extra porosity allows the deposition of large functional molecules in the defective framework to manipulate the adsorption properties. Compared to the defect-free UiO-66, which is a N₂-selective adsorbent, a O₂-selective adsorbent is demonstrated by introducing ferrocene into the defective framework of UiO-66.