Reversible MOF-Based mixed matrix membranes for SO2/N2 separation: A photo-responsive approach

Abstract

Fuel consumption for industrial development, SO₂ gas emissions are increasing year by year and have become a focal point of air pollution. Membrane separation method photo-responsive materials and MOFs have attracted more and more attention in a variety of fields. This is because the membrane separation method uses less energy and is an uncomplicated process; MOFs have superior gas adsorption capabilities; and the photo-responsive materials are controllable. In this study, mixed matrix membranes are prepared using Uio-66-NH₂ and photo-responsive materials CE-Azo-Uio-66 as fillers and Pebax as base membranes. By improving the dissolution-diffusion mechanism for SO₂ gas molecules, SO₂/N₂ gas separation is accomplished. More channels for the mass transport of SO₂ gas through the membrane can be created by MOFs increased porosity and larger specific surface area. Secondly, the SO₂ adsorption and dissolution-diffusion mechanism of the mixed matrix membrane are strengthened by the grafted SO₂ affinity groups on the MOF. Moreover, Pebax/CE-Azo-Uio-66 membranes is not only significantly more permeation selective than Pebax/Uio-66-NH₂ membranes, but also shows photo-responsive characteristic. The SO₂ permeability and selectivity of Pebax/CE-Azo-Uio-66 mixed matrix membranes at CE-Azo-Uio-66 content of 20 % are increased by 191 % and 179 %, respectively, compared to pure Pebax membranes. It is also found that the SO₂ permeability and SO₂/N₂ selectivity of the membranes show regularly reversible changes at the UV–Vis photoconversion conditions of Pebax/CE-Azo-Uio-66-20 % membranes, indicating the photo-responsive characteristics of mixed matrix membranes that include Azo groups. The SO₂ permeability of the Pebax/CE-Azo-Uio-66 membrane is increased by 1300 Barrer and the SO₂/N₂ selectivity is increased by 350 when the light source is changed from UV to Vis light, achieving a controlled separation of SO₂/N₂. Besides, the addition of MOF particles significantly enhances the mechanical properties and stability of the membrane.