Abstract
Several concepts of membranes have emerged, aiming at the enhancement of separation performance, as well as some other physicochemical properties, of the existing membrane materials. One of these concepts is the well-known mixed matrix membranes (MMMs), which combine the features of inorganic (e.g., zeolites, metal–organic frameworks, graphene, and carbon-based materials) and polymeric (e.g., polyimides, polymers of intrinsic microporosity, polysulfone, and cellulose acetate) materials. To date, it is likely that such a concept has been widely explored and developed toward low-permeability polyimides for gas separation, such as oxydianiline (ODA), tetracarboxylic dianhydride–diaminophenylindane (BTDA-DAPI), m-phenylenediamine (m-PDA), and hydroxybenzoic acid (HBA). When dealing with the gas separation performance of polyimide-based MMMs, these membranes tend to display some deficiency according to the poor polyimide–filler compatibility, which has promoted the tuning of chemical properties of those filling materials. This approach has indeed enhanced the polymer–filler interfaces, providing synergic MMMs with superior gas separation performance. Herein, the goal of this review paper is to give a critical overview of the current insights in fabricating MMMs based on chemically modified filling nanomaterials and low-permeability polyimides for selective gas separation. Special interest has been paid to the chemical modification protocols of the fillers (including good filler dispersion) and thus the relevant experimental results provoked by such approaches. Moreover, some principles, as well as the main drawbacks, occurring during the MMM preparation are also given.
Highlights
Membrane gas separation (GS) today is one of the latent ways in separating several types of organic and inorganic gases, such as CO2, H2, CH4, CO, O2, He, and Ar, among others (Budd et al, 2005; Baker, 2012; Castro-Muñoz et al, 2017)
It has been identified that such interfacial gaps can be formed by two different factors: (i) the nature of the polymer–filler interaction and (ii) the stress carried out during the Mixed matrix membrane (MMM) preparation
The chemical property tuning of filler materials was initiated with the chemical modification of zeolites
Summary
Membrane gas separation (GS) today is one of the latent ways in separating several types of organic and inorganic gases, such as CO2, H2, CH4, CO, O2, He, and Ar, among others (Budd et al, 2005; Baker, 2012; Castro-Muñoz et al, 2017). The concept of an MMM deals with the incorporation of inorganic materials (well-known as fillers) into the organic polymer structure (Castro-Muñoz et al, 2018b,c), ideally generating a new composite membrane with an enhanced GS performance. Due to their different phases and dissimilar inherent characteristics, defects are usually observed especially at polymer–filler interface regions, leading to lower than theoretically possible performance enhancement (Iyer et al, 2010; Valero et al, 2014; CastroMuñoz and Fíla, 2018). The principles, main drawbacks, and defect types generated in the MMM preparation are discussed
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