Enhancing the Gas Separation Selectivity of Mixed-Matrix Membranes Using a Dual-Interfacial Engineering Approach
Chunhui Wu, Kexin Zhang, Hongliang Wang, Yaqi Fan, Songwei Zhang, Sanfeng He, Fang Wang, Yu Tao, Xiaowen Zhao, Yue‐Biao Zhang, Yanhang Ma, Yongjin Lee, Tao Li
Abstract
We report a dual-interfacial engineering approach that uses a sub-20 nm polycrystalline MOF-74 shell as a transition phase to engineer the MOF–polymer interface. The application of a shell MOF layer divides the original single interface problem into two interfaces: MOF–MOF and MOF–polymer, which can be individually addressed. The greater external surface area created by the uneven MOF-74 shell containing high-density open metal sites allows the MOF to interact with 300% polymer at the interface compared to traditional MOF, thereby ensuring good interfacial compatibility. When applied on UiO-66-NH2, its respective mixed-matrix membranes exhibit a simultaneous increase of CO2/CH4 separation selectivity and CO2 permeability with increasing MOF loading, implying a defect-free interface. When applied on MOF-801, the mixed-matrix membranes exhibit an ethylene/ethane separation selectivity up to 5.91, a drastic 76% increase compared to that of the neat polymer owing to a “gas focusing” mechanism promoted by the preferred pore orientation in the MOF-74 layer. This represents one of the most selective ethylene/ethane separation membranes reported to date.