Incorporation of bifunctional aminopyridine into an NbO-type MOF for the markedly enhanced adsorption of CO2 and C2H2 over CH4

Abstract

The development of porous MOFs exhibiting highly selective C₂H₂/CH₄ and CO₂/CH₄ separations is quite important to meet the requirement of high-purity C₂H₂ and CH₄ in various industries. By employing a ligand heterobifunctionalization strategy, we designed and synthesized an aminopyridine-functionalized diisophthalate ligand, and successfully targeted its corresponding copper-based NbO-type MOF ZJNU-98. Gas adsorption studies revealed that ZJNU-98 exhibited significantly enhanced adsorption of C₂H₂ and CO₂ over CH₄ compared to its parent MOF, NOTT-101. At 298 K and 1 atm, C₂H₂ and CO₂ uptakes of ZJNU-98 are 10.0% and 16.7% higher than the corresponding values of NOTT-101, while 14.2% and 18.8% increases in C₂H₂/CH₄ and CO₂/CH₄ adsorption selectivities were observed for the equimolar gas mixtures in ZJNU-98 compared to NOTT-101. Furthermore, the contribution of the functional group effect on gas adsorption has been assessed, demonstrating that the amine group plays a more important role than the pyridinic-N atom despite its lower Lewis basicity. This work provided an effective way and significant experimental evidence for the design of new porous MOFs with highly enhanced gas adsorption performance.