Pebax mixed matrix membrane with bimetallic CeZr-MOFs to enhance CO2 separation

Abstract

Amine-functionalized and metal doped metal–organic frameworks (MOFs) will enable further enhancement of CO2 adsorption, which holds great promise in mixed matrix membranes (MMMs) for CO2/N2 separation. Four kinds of UiO66 with different sizes have been successfully fabricated by introduction of Ce and/or amino groups in UiO66. The influence of Ce doping on the UiO66 is greatly related to the ligand. Compared with ZrUiO66, the CeZrUiO66 has bigger particle size, lower BET specific surface area and pore volume and a worse CO2 adsorption capacity. Interestingly, the tendency of Ce-doped ZrUiO66-NH2 is contrary to the aforementioned. In particular, bimetallic CeZrUiO66-NH2 has an ultramicroporous structure, small particle size, rich crystal defect, superb CO2 capture capacity and high CO2/N2 adsorption selectivity, suggesting that the simultaneous introduction of Ce and amino groups is conducive to the enhancement of CO2 separation. The intrinsic ultramicroporous structure of CeZrUiO66-NH2 not only offers fast and low resistance transport channels for CO2, but also supplies more sites for CO2 adsorption owning to the doping of Ce and the amino groups. As a result, Pebax/CeZrUiO66-NH2 (3 wt%) MMMs show the CO2 permeability of 100.7 Barrer and the CO2/N2 ideal selectivity of 76.4, which is close to Robeson upper bound from 2008. Meanwhile, the Pebax/CeZrUiO66-NH2 (3 wt%) MMMs present relatively good pressure resistance, which would be advantageous in terms of industrial application.