Selective adsorption of CO2/N2 promoted by polar ligand functional groups of metal–organic frameworks

Abstract

The structure modification of metal–organic frameworks (MOFs) is a promising technique to enhance its selective adsorption of carbon dioxide at room temperatures. However, to date, little is known on the structure-property relationship of MOFs for carbon capture. In this work, the effects of chemical composition of MOFs on selective adsorption of carbon dioxide were studied systematically. A series of aluminum-based MIL-53 with similar formula units but different organic ligands, Al(OH)BDC-X [BDC\u2009=\u2009terephthalate, X\u2009=\u2009H, NH2, NO2, 2(CH3)], were prepared and employed to the selective adsorption of CO2/N2. It was found that the Al(OH)BDC-X series with various organic ligands affected the CO2 capacity significantly. The decorations of functional groups with strong polarity on the BDC links remarkably enhanced the CO2 uptakes. The experimental results were in good agreement with the equivalent adsorption heat calculations, which showed that the CO2 affinity of the ligands with polarity groups were thermodynamically more favored than those with non-polarity ones on the MOF structures. The interesting findings could provide a potential way to fabricate new metal organic frameworks with high carbon dioxide capture capacities at room temperature.