Design of Pore Properties of an Al-Based Metal-Organic Framework for the Separation of an Ethane/Ethylene Gas Mixture via Ethane-Selective Adsorption

Abstract

A series of Al-based isomorphs (CAU-10H, MIL-160, KMF-1,and CAU-10pydc)were synthesized using isophthalic acid (ipa), 2,5-furandicarboxylicacid (fdc), 2,5-pyrrole dicarboxylic acid (pyrdc), and 3,5-pyridinedicarboxylicacid (pydc), respectively. These isomorphs were systematically investigatedto identify the best adsorbent for effectively separating C2H6/C2H4. All CAU-10 isomorphs exhibitedpreferential adsorption of C2H6 over that ofC(2)H(4) in mixture. CAU-10pydc exhibited the bestC(2)H(6)/C2H4 selectivity(1.68) and the highest C2H6 uptake (3.97 mmolg(-1)) at 298 K and 1 bar. In the breakthrough experimentusing CAU-10pydc, 1/1 (v/v) and 1/15 (v/v) C2H6/C2H4 gas mixtures were successfully separatedinto high-purity C2H4 (>99.95%), with remarkableproductivities of 14.0 L-STP kg(-1) and32.0 L-STP kg(-1), respectively, at 298K. Molecular simulations revealed that the exceptional separationperformance of CAU-10pydc originated from the increased porosity andreduced electron density of the pyridine ring of pydc, leading toa relatively larger decrease in pi-pi interactionswith C2H4 than in the C-H center dot center dot center dot pi interactions with C2H6. This study demonstratesthat the pore size and geometry of the CAU-10 platform are modulatedby the inclusion of heteroatom-containing benzene dicarboxylate orheterocyclic rings of dicarboxylate-based organic linkers, therebyfine-tuning the C2H6/C2H4 separation ability. CAU-10pydc was determined to be an optimum adsorbentfor this challenging separation.