Vanadium (IV) benzenedicarboxylate: A novel adsorbent for selective separations

The crystal structure of VOBDC (BDC = 1,4-benzenedicarboxylate) has a 1-dimensional channel system with apertures of ∼8 Å, and shows remarkable flexibility upon adsorption/desorption of various guest molecules in the channels. VOBDC can selectively and rapidly adsorb organic molecules containing sulfur on exposure to a 5% CH₄/He stream with different contents of thiophene or dimethyl sulfide at ambient temperature. Selective uptake of thiophene from liquid octane with thiophene concentrations from 2000 ppmw down to 100 ppmw is also observed. X-ray crystallographic data show that the adsorbed thiophene molecules adopt a herringbone packing arrangement within the channels of VOBDC while adsorbed dimethyl sulfide molecules are disordered among several positions in the channels with the sulfur atoms pointing toward the channel walls. The observed adsorptive capacities for thiophene and dimethyl sulfide are 155 mg and 208 mg sulfur per gram of VOBDC, respectively, consistent with the crystal structure data.