Constructing mixed matrix membranes for CO2 separation based on light lanthanide fluoride nanosheets with mesoporous structure

The incorporation of porous nano-fillers into mixed matrix membranes (MMMs) has a great impact on CO2 separation. In this study, a series of F-Ln (Ln is the Light Lanthanide, Ln = La, Ce, Pr, Nd) nanosheets with mesoporous structure was fabricated as a filler in Pebax®1657 matrix to improve the performance of CO2 separation. F-Ln nanosheets are uniformly distributed in the membrane and the mesoporous structure can construct multiple channels for CO2 fast transport in Pebax/F-Ln MMMs. The pore diameter of nanosheet is in order: F-La > F-Ce > F-Pr > F-Nd, and the smaller pore diameter of nanosheets is beneficial to improve the CO2 separation performance. In humidified conditions, Pebax/F-Nd-6 MMMs show optimum separation performance among MMMs, and the CO2 permeability is up to 1265 Barrer and CO2/CH4 selectivity is 36.7, which are 2.3 times and 1.9 times higher than pure Pebax and approaches 2019 upper bound. Meanwhile, to demonstrate the potential universal applicability of F-Ln nanosheets in CO2 separation, XLPEO/F-Ce MMMs were fabricated to separate CO2/N2 and the performance exceeds the 2019 upper bound. The efficient CO2 separation performance of 2D F-Ln nanosheets with mesoporous structure in membranes reveals the potential application of these nanosheets in industrial CO2 separation.