Synthesis and O2 Reactivity of a Titanium(III) Metal–Organic Framework

• Published in: Inorganic chemistry 2015-10, Vol.54 (20), p.10096-10104
• Main Authors: Mason, Jarad A, Darago, Lucy E, Lukens, Wayne W, Long, Jeffrey R
• Format: Article
• Language: English
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/acs.inorgchem.5b02046

Metal–organic frameworks featuring pores lined with exposed metal cations have received attention for a wide range of adsorption-related applications. While many frameworks with coordinatively unsaturated MII centers have been reported, there are relatively few examples of porous materials with coordinatively unsaturated MIII centers. Here, we report the synthesis and characterization of Ti3O­(OEt)­(bdc)3(solv)2 (Ti-MIL-101; bdc2– = 1,4-benzenedicarboxylate; solv = N,N-dimethylformamide, tetrahydrofuran), the first metal–organic framework containing exclusively TiIII centers. Through a combination of gas adsorption, X-ray diffraction, magnetic susceptibility, and electronic and vibrational spectroscopy measurements, this high-surface-area framework is shown to contain five-coordinate TiIII centers upon desolvation, which irreversibly bind O2 to form titanium­(IV) superoxo and peroxo species. Electronic absorption spectra suggest that the five-coordinate TiIII sites adopt a distorted trigonal-bipyramidal geometry that effectively shields nuclear charge and inhibits strong adsorption of nonredox-active gases.