High-pressure separation performance of Ni(TMBDC)(DABCO)0.5 featured low-polarity channel for CH4/N2 mixture

Abstract

Developing adsorbents with exceptional CH4/N2 selectivity under high pressure is a crucial commercial requirement and a significant technical challenge for the industrial high-pressure swing adsorption (HPSA) in CH4/N2 separation. Only a few adsorbents were reported to address this issue. In this work, we aimed to explore two microporous MOFs with low-polarity channels for high-pressure CH4/N2 separation. The Ni(BDC)(DABCO)0.5 and its isostructural analog Ni(TMBDC)(DABCO)0.5 were synthesized, characterized, and examined for high-pressure CH4/N2 adsorption property. Due to the lower polarity channel originating from tetramethyl groups, Ni(TMBDC)(DABCO)0.5 exhibited an exceptional methane capacity of 4.23 mmol/g and an IAST selectivity of 5.1 for the CH4/N2 binary mixture at a pressure of 10 bar, surpassing the majority of previously reported materials. The GCMC simulation revealed that the low-polarity pore surfaces in both materials exhibited a higher affinity for CH4 molecules compared to N2 molecules, under both ambient and high pressures. The breakthrough experiments showed that Ni(TMBDC)(DABCO)0.5 exhibited excellent dynamic separation towards CH4/N2 under both 1 bar and 5 bar, indicating great potential as an emerging candidate for the recovery of CH4 from coal-mine methane in industrial PSA processes.