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, Cu(I)Cl(ttcH(3)) (ttcH(3) = trithiocyanuric acid), 1, in aqueous ammonia solution yields monoliths of amorphous Cu(I) (1.8)(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 × 10(–11) S cm(–1) at 20 °C to 7.6 × 10(–9) S cm(–1) at 140 °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.