MOF-layer composite polyurethane membrane increasing both selectivity and permeability: Pushing commercial rubbery polymer membranes to be attractive for CO2 separation

Abstract

We demonstrated a novel MOF-layer composite membrane consisting of three layers, based on a polyurethane/PIM layer and a UiO-66-NH2 layer to separate CO2/N2 mixture. A small amount of PIM (i.e., ≤10 wt% PIM in PU) could completely dissolve in PU. After blending it with PU, it could use its own porosity to increase the CO2 permeability of the PU/PIM polymer blend layer. UIO66-NH2 was prepared into a 10 μm thick MOF layer by spin coating. The densely packed MOF in this layer brings abundant adsorption sites to enrich CO2, thereby bringing high selectivity to the composite film. These unique two layers simultaneously increase permeability and CO2/N2 selectivity, and the PAN-UIO66-NH2-PU/PIM (10 wt%) composite membrane displayed a CO2 permeance of 333 Barrer and a CO2/N2 selectivity of 138, its performance can easily exceed the 2008 CO2/N2 upper bound. Moreover, the entanglement of its molecular chain with PIM slows down the aging, leading a more consistent selectivity performance over a sixty-day-ageing study period. This attractive separation performance of PAN-UIO66-NH2-PU/PIM provides an exciting platform for rubbery polymer membranes to economically separate CO2 and makes commercial PU an attractive option for large-scale industrial CO2 separation.