Preparation of ZIF-8@[C2mim][BF4]/Pebax mixed-matrix membranes through a impregnation strategy for enhancing the separation of difluoromethane (R32) from refrigerant blend R410A

Abstract

R410A is a high GWP (2088) refrigerant blend soon to be eliminated, consisting of equal mass of difluoromethane (R32) and pentafluoroethane (R125). R32 is a good additive to the next generation refrigerant hydrofluoroolefin due to low GWP (675) and superior thermodynamic properties. But the separation of R32 and R125 by conventional distillation is a challenge because of their near boiling points. In this study, innovative membranes combining metal-organic framework (MOF) and ionic liquid (IL) are applied to the recovery of valuable R32 from R410A and demonstrate excellent R32/R125 separation performance. [C2mim][BF4] was embedded into the nanocages of ZIF-8 through a impregnation strategy to prepare ZIF-8@[C2mim][BF4]/Pebax mixed-matrix membranes (MMMs). Characterization results confirmed that IL was successfully added to the nanocages of ZIF-8. ZIF-8@[C2mim][BF4]/Pebax MMMs with 10 wt% loading exhibits the best separation performance, increasing R32 permeability and R32/R125 selectivity by 177% and 150% compared to neat Pebax membrane. The ZIF-8 @ [C2mim][BF4] material by impregnation has excellent performance in regulating the effective cage size of MOF, providing new strategies for designing more accurate and efficient MMMs.