Methyl-functionalized microporous metal-organic framework for efficient SF6/N2 separation

The capture and separation of sulfur hexafluoride (SF6) from nitrogen (N2) has the potential to reduce greenhouse gas emissions and provide economic benefits to the semiconductor industry. Herein, a series of metal–organic frameworks (MOFs) with different pore environments (Ni(pba)2 (pba = 4-(4-pyridyl)benzoate), Ni(3-mpba)2 (3-mpba = 3-methyl-4-(4-pyridyl)benzoate), and Co(3-mpba)2) were designed and synthesized for SF6/N2 separation. The most promising candidate is Ni(3-mpba)2, which exhibits excellent SF6 uptake capacity (63.4 cm3 g−1 at 298 K and 100 kPa) and the highest SF6/N2 selectivity (221 at 298 K and 100 kPa). X-ray diffraction analysis and theoretical calculations indicate that introducing the methyl group into Ni(3-mpba)2 alters the microchemical environment of the pores. Ni(3-mpba)2 has a smaller pore structure and more binding sites than Ni(pba)2; its structure and binding sites enhance the affinity between sulfur hexafluoride and the adsorbent. Dynamic breakthrough experiments further verify the remarkable separation performance of Ni(3-mpba)2 under simulated actual working conditions. In combination with its excellent regeneration ability and cycling performance, this porous coordination network shows great promise for SF6/N2 separation.