A Robust Hydrogen-Bonded Metal–Organic Framework with Enhanced Ethane Uptake and Selectivity

Selective adsorption of trace C 2 H 6 over C 2 H 4 is important for the industrial purification of polymer-grade C 2 H 4 (>99.95% purity). For practical applications, potential adsorbents show high structural stability while maintaining elevated C 2 H 6 adsorption even at low pressures. Herein, we report a C 2 H 6 -selective metal–organic framework (MOF), viz., Co(AIN) 2 (HAIN = 3-aminoisonicotinic acid), with a twofold interpenetrated dia structure. Compared to an isoreticular and unstable Co(IN) 2 (HIN = isonicotinic acid) without internal hydrogen bonding, this framework exhibits exceptional structural robustness even under humid conditions because of the presence of intra- and inter-net hydrogen bonds between carboxylate oxygens and amino groups of AIN – . Decoration of the internal polar pore surfaces with groups that form extensive hydrogen bonds offers a more favorable environment for selective C 2 H 6 adsorption. According to the ideal adsorbed solution theory, the predicted selectivity for C 2 H 6 /C 2 H 4 was found to be 2.98 in C 2 H 6 /C 2 H 4 (1:15, v/v) mixtures, which surpasses even the best-performing MOFs. The C 2 H 6 uptake at 62.5 mbar partial pressure in the single-component isotherm, in C 2 H 6 /C 2 H 4 (1:15, v/v) mixtures, was the highest (63.16 cm 3 g –1 ) among MOF adsorbents, along with a nearly top-tier separation potential (116.03 cm 3 g –1 ). Molecular modeling illustrates that the C–H···π interactions of C 2 H 6 with the pore walls are more significant than those of C 2 H 4, accounting for the improved selectivity for C 2 H 6 over C 2 H 4 in Co(AIN) 2 . The separation performance under dynamic dry and humid conditions was confirmed by breakthrough experiments. Co(AIN) 2 was shown to be synthesized on a gram scale and was easily regenerated by inert gas purging. Thus, we demonstrated that coating of internal pore surfaces with groups that form hydrogen bonds provides more favorable environments for enhanced structural stability and C 2 H 6 affinity and selectivity.