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

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, (CuCl)-Cl-I(ttcH(3)) (ttcH(3) = trithiocyanuric acid), 1, in aqueous ammonia solution yields monoliths of amorphous Cu-1.8(I)(ttc)(0.6)(ttcH(3))(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 x 10(-11) S cm(-1) at 20 degrees C to 7.6 x 10(-9) S cm(-1) at 140 degrees 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.