Mixed-matrix membranes based on semi-oxidation MXene modified g-C3N4 nanosheet for enhanced CO2 separation

While mixed matrix membranes (MMMs) containing two-dimensional (2D) layered materials (such as, GO, g-C 3 N 4 and MXene , etc.) have revealed potential application prospects for gas separation applications, it still faces a serious challenge to enhance the performance of CO 2 separation. Owing to the structural defects of g-C 3 N 4 nanosheets produced during the exfoliation process, which has greatly reduced the gas selectivity. Herein, we describe the construction of g-C 3 N 4 -MXene/Pebax MMM composed by MXene modified the structural defects in g-C 3 N 4 nanosheets to surmount the low gas selectivity of g-C 3 N 4 membrane. However, the stacking of nanosheets on each other hinder the gas transport channels. The TiO 2 nanoparticles derived in-situ from MXene semi-oxidation can support an intermediate layer between g-C 3 N 4 nanosheet and MXene nanosheet to expand the gas transport channels. Eventually, a novel g-C 3 N 4 -TiO 2 @MXene/Pebax MMM was obtained that exhibited maximum CO 2 permeability of 1673.69 Barrer in separation of CO 2 /CH 4 , CO 2 /N 2 selectivity of 45.13, and CO 2 /CH 4 selectivity of 47.76, exceeding the bond 2008 limit on Robeson. What's more, the MMM within 100 h (1 bar and 298 K) are measured to have outstanding separation performance. Overall, this concept offers a novel strategy to enhance CO 2 separation by MXene modified defects in g-C 3 N 4 nanosheets.