Amino-functionalized NUS-8 nanosheets as fillers in PIM-1 mixed matrix membranes for CO2 separations

Membrane-based separation technologies are promising for various applications such as carbon capture and storage (CCS). Herein, we report the preparation and performance of mixed matrix membranes (MMMs) for carbon dioxide (CO2) separation. The MMMs comprise amino-functionalized metal-organic framework (MOF) nanosheets (NUS-8-NH2) dispersed in the polymer of intrinsic microporosity 1 (PIM-1). Specifically, the MOF nanosheets were synthesized through a bottom-up method and introduced into the PIM-1 matrix to fabricate NUS-8-NH2/PIM-1 MMMs. The uniformly dispersed MOF nanosheets could afford additional fast transport pathways through intra-flake pores and inter-flake nano-channels. Moreover, the amino groups could enhance CO2 transport within NUS-8-NH2/PIM-1 MMMs. In addition, hydrogen bonding between the NUS-8-NH2 filler and PIM-1 matrix improved interfacial compatibility. Therefore, the as-prepared MMMs could achieve a high filler loading of 15 wt% without sacrificing separation performance. Compared with the pure PIM-1 membrane, the MMM with 10 wt% NUS-8-NH2 showed CO2 permeability of ∼14000 Barrer and a CO2/N2 selectivity of ∼30, surpassing the 2008 Robeson's upper bound.