Hydrocarbon adsorption in a series of mesoporous metal-organic frameworks

Abstract A series from five mesoporous metal-organic frameworks [Zn12(i-bdc)6(G)6(dabco)3] (i-bdc = isophthalate, G = one of the following: ethylenediolate, 1,2-propylenediolale, 1,2-buthylenediolate, 1,2-pentylenediolate, glycerolate), denoted as NIIC-20-G, show appreciable methane gravimetric adsorption uptakes at high pressure (56 atm), up to 210 cm3⋅g−1 at 273 K and 156 cm3⋅g−1 at 295 K. The corresponding volumetric uptakes reach 175 cm3⋅cm−3 at 273 K and 130 cm3⋅cm−3 at 295 K, approaching to the best reference data for other MOFs. The highest deliverable methane capacity at 295 K was calculated to be 73 cm3⋅cm−3 (pressure range 35–5 atm) and 109 cm3⋅cm−3 (pressure range 65–5 atm). The NIIC-20-G compounds also demonstrate great adsorption capacity towards various volatile organic compounds (benzene, cyclohexane, xylene isomers), irrespective on the chemical nature or geometry of the substrate. The highest vapor adsorption data at 298 K are 6.9 mmol⋅g−1 for the benzene, 5.4 mmol⋅g−1 for the cyclohexane, 4.4 mmol⋅g−1 for o-xylene, 4.5 mmol⋅g−1 for m-xylene and 4.6 mmol⋅g−1 for p-xylene. The compounds NIIC-20-G were shown to maintain their crystal structures as well as their vapor adsorption properties during multiple repeating experiments. Remarkably, the full regeneration of the porous materials could be carried out upon only a mild heating (60 °C). Great adsorption of various volatile hydrocarbons at low concentrations during several cycles and rather mild energy requirements for the material regeneration suggests promising perspectives of NIIC-20-G compounds in air purification applications.