Enhanced gas sorption properties of a new sulfone functionalized aluminum metal-organic framework: Synthesis, characterization, and DFT studies

A new sulfone-functionalized analogue of DUT-5 ([Al(OH) (BPDC)], BPDC = 4,4'-biphenyldicarboxylate) microporous metal-organic framework,[Al(OH) (SBPDC)] (1) (H₂SBPDC = 2,2'-sulfone-4,4'-biphenyldicarboxylate), has been synthesized in order to achieve better gas sorption properties over DUT-5. The compound was characterized by powder X-ray diffraction (PXRD), scanning electron microscopy, variable temperature PXRD, thermogravimetric analysis, FT-IR spectroscopy, NMR spectroscopy and gas adsorption measurements. The new MOF forms a 3D porous framework containing 1D inorganic chains which are formed by corner-sharing octahedral AlO₆ connected through SBPDC linkers. As determined by gas sorption measurements, the compound 1 exhibits high porosity with the H₂ uptake capacity of 8.58 mmol g^-1 at 77 K (1 atm) and CO₂ uptake of 2.51 mmol g^-1 at 298 K (1 atm) or 4.40 mmol g^-1 at 273 K (1 atm). The gas sorption experimental results suggested that compound 1 with sulfone functionalized ligand showed higher CO₂ and H₂ gas uptake than that of isoreticular MOF, DUT-5. The CO₂ gas sorption behavior of 1 and DUT-5 has been analyzed with the aid of DFT studies which explained that the sulfone group can enhance the efficiency of CO₂ uptake.