Metal-Organic Framework/2d Boron Nitride Nanosheets Composite Fillers in Mixed Matrix Membranes for H2 /Co2 Separation

Abstract

Nanometer-thick two-dimensional (2D) materials are becoming ideal fillers for designing mixed matrix membranes (MMMs) with high gas permeability and selectivity due to their unique structures. ZIF-67@BNNS composite fillers were prepared by combining boron nitride nanosheets (BNNS), a thermally stable and chemically inert two-dimensional material, with the metal-organic framework ZIF-67. By incorporating these materials into polyethyleneimine (PEI), MMMs with efficient hydrogen (H2) separation performance were developed. The -NH2 groups on the BNNS surface provide a growth site for cobalt (Co) ions, facilitating the construction of a two-dimensional continuous channel by growing a ZIF-67 layer in situ on the BNNS surface. The inherent micropores of ZIF-67 form internal channels for gas transport within the composite packing, enhancing gas permeability. The interlaced BNNS layer creates an external channel for gas transport, increasing resistance and thereby contributing to improved gas selectivity. At a low loading of 1 wt%, the PEI/ZIF-67@BNNS-0.2 MMMs exhibited a 150% increase in H2 permeability and 89% improvement in H2/CO2 selectivity compared to pure PEI membranes. Additionally, these MMMs demonstrate strong thermal stability and mechanical properties, making them highly promising for H2 separation applications.

Keywords: Gas separation, MOFs, Mixed matrix membrane, BNNS