Engineering microporous ethane-trapping metal-organic frameworks for boosting ethane/ethylene separation.

Realization of ethane-trapping materials for separating ethane (CH) from ethylene (CH) by adsorption, to potentially replace the energy-intensive cryogenic distillation technology, is of prime importance in the petrochemical industry. It is still very challenging to target CH-selective adsorbents with both high CH capture capacity and gas selectivity. Herein, we report that a crystal engineering or reticular chemistry strategy enables the control of pore size and functionality in a family of isomorphic metal-organic frameworks (MOFs) for boosting the CH uptake and selectivity simultaneously. By altering the carboxylic acid linker in Ni(bdc)(ted), we developed two novel isoreticular MOFs, Ni(ndc)(ted) and Ni(adc)(ted) (termed ZJU-120 and ZJU-121, respectively), in which the pore sizes and nonpolar aromatic rings can be finely engineered. We discover that activated ZJU-120a with the optimized pore size (4.4 Å) and aromatic rings exhibits both a very high CH uptake (96 cm g at 0.5 bar and 296 K) and CH/CH selectivity (2.74), outperforming most of the CH-selective MOFs reported. Computational studies indicate that the suitable pore size and more nonpolar aromatic rings on the pore surfaces of ZJU-120a mainly contribute to its exceptional CH uptake and selectivity. The breakthrough experiments demonstrate that ZJU-120a can efficiently separate CH from 50/50 and 10/90CH/CH mixtures under ambient conditions.