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

Realization of ethane-trapping materials for separating ethane (C2H6) from ethylene (C2H4) 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 C2H6-selective adsorbents with both high C2H6 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 C2H6 uptake and selectivity simultaneously. By altering the carboxylic acid linker in Ni(bdc)(ted)(0.5), we developed two novel isoreticular MOFs, Ni(ndc)(ted)(0.5) and Ni(adc)(ted)(0.5) (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 angstrom) and aromatic rings exhibits both a very high C2H6 uptake (96 cm(3) g(-1) at 0.5 bar and 296 K) and C2H6/C2H4 selectivity (2.74), outperforming most of the C2H6-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 C2H6 uptake and selectivity. The breakthrough experiments demonstrate that ZJU-120a can efficiently separate C2H6 from 50/50 and 10/90C(2)H(6)/C2H4 mixtures under ambient conditions.