Host-Guest Pore Space Partition in a Boron Imidazolate Framework for Ethylene Separation

Separation of ethylene (C2H4) from ethane (C2H6) through one step is desirable but challenging in view of their similar sizes and physical properties. Introduction of pore partition agents into metal-organic frameworks (MOFs) endows materials with multivariate porous environments for gas adsorption and separation. Here, we report a novel microporous boron imidazolate framework (BIF-108-Zn) that integrates both organic ligands and extra-framework species as pore partition agents to divide the interconnected channels into isolated cages. This structure possesses a high pore volume with a reduced pore size and a functionalized pore surface to realize preferential binding of C2H6 over C2H4. Dynamic breakthrough measurements demonstrated that BIF-108-Zn can directly produce polymer-grade C2H4 with a productivity of 0.69 mmol/g at 298 K and 1 bar from a binary mixture of C2H6/C2H4. Furthermore, the relatively low isosteric enthalpy value endows it with good regenerability and high stability, as verified by multiple adsorption separation tests.

Automated summary

A novel microporous boron imidazolate framework (BIF-108-Zn) has been reported for efficient separation of ethylene and ethane by integrating organic ligands and extra-framework species as pore partition agents. The structure features high pore volume, reduced pore size, and functionalized pore surface for preferential binding of ethane. Dynamic breakthrough measurements show that BIF-108-Zn can produce polymer-grade ethylene with good regenerability and high stability.