Mixed matrix membranes containing composite nanosheets with three-dimensional nanopores for efficient CO2 separation

Abstract

Novel composite nanosheets with three-dimensional (3D) nanopores were used as nanofillers and filled in Pebax® MH 1657 (Pebax) matrix to fabricate mixed matrix membranes (MMMs) for highly efficient CO2/CH4 separation. The nanosheets were formed by anchoring zeolite imidazolate framework-8 (ZIF-8) on the surface of the porous graphitic carbon nitride (g-C3N4). For the composite nanosheets of ZIF-8/g-C3N4, the interconnected 3D nanopores of ZIF-8 on composite nanosheets provided high selective nanochannels in MMMs, thereby improving CO2/CH4 selectivity. Meanwhile, the randomly arranged nanosheets were acted as the ultrafast CO2 transport freeways in MMMs, thus enhancing CO2 permeability. The as-prepared Pebax/ZIF-8/g-C3N4 exhibited an excellent CO2 separation performance. In particular, Pebax/ZIF-8/g-C3N4–9 MMM showed the highest separation performance, which reached 553 ± 23 Barrer and 35.5 ± 0.67 for CO2 permeability and CO2/CH4 separation factor, respectively. The composite nanosheets with 3D nanopores provided an effective strategy to fabricate high-performance MMMs for gas separations.