Topochemical conversion of a dense metal-organic framework from a crystalline insulator to an amorphous semiconductor

By Tominaka, S.; Hamoudi, H.; Suga, T.; Bennett, T. D.; Cairns, A. B. & Cheetham, A. K.
Published in Chem. Sci. The Royal Society of Chemistry 2015

Abstract

The topochemical conversion of a dense, insulating metal-organic framework (MOF) into a semiconducting amorphous MOF is described. Treatment of single crystals of copper(i) chloride trithiocyanurate, CuICl(ttcH3) (ttcH3 = trithiocyanuric acid), 1, in aqueous ammonia solution yields monoliths of amorphous CuI1.8(ttc)0.6(ttcH3)0.4, 3. The treatment changes the transparent orange crystals of 1 into shiny black monoliths of 3 with retention of morphology, and moreover increases the electrical conductivity from insulating to semiconducting (conductivity of 3 ranges from 4.2 [times] 10-11 S cm-1 at 20 [degree]C to 7.6 [times] 10-9 S cm-1 at 140 [degree]C; activation energy = 0.59 eV; optical band gap = 0.6 eV). The structure and properties of the amorphous conductor are fully characterized by AC impedance spectroscopy, X-ray photoelectron spectroscopy, X-ray pair distribution function analysis, infrared spectroscopy, diffuse reflectance spectroscopy, electron spin resonance spectroscopy, elemental analysis, thermogravimetric analysis, and theoretical calculations.

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