Metal‐Organic Frameworks: Frameworks in Mixed‐Matrix Membranes

Abstract

Gas separation performances of polymer membranes can be improved by addition of metal–organic frameworks (MOFs). Mixed‐matrix membranes (MMMs) with MOFs as additives (fillers) have increased permeabilities and often also selectivities compared to the pure polymer. Incorporation of MOFs into polysulfone and Matrimid ® polymers for MMMs gives defect‐free membranes with performances similar to the best polymer membranes for gas mixtures, such as O 2 /N 2 , H 2 /CH 4 , CO 2 /CH 4 , H 2 /CO 2 , CH 4 /N 2 , and CO 2 /N 2 (preferentially permeating gas is named first). The MOF porosity, its particle size, and content in the MMM are factors to influence the permeability and the separation performance of the membranes.

Enhancing Mixed-Matrix Membrane Performance with Metal–Organic Framework Additives

“…The addition of fillers to polymer materials can also meet the challenges of commercially used polymer materials, like membrane plasticization, low contaminant resistance, and low product purity and provide high performance gas separation MMMs, on the condition that defects at the filler–polymer interphase can be avoided. Various porous or nonporous inorganic additives have been tested as filler materials. ,,,,− Improvements in membrane separation performance are expected for nanostructured porous additives such as zeolites or MOFs with size-selective adsorption and separation properties. , Concerning the filler, its chemical properties, functional groups on the surface, the distribution of particle sizes, and its shape are other important variables.…”

Mixed-Matrix Membranes of the Air-Stable MOF-5 Analogue [Co4(μ4-O)(Me2pzba)3] with a Mixed-Functional Pyrazolate-Carboxylate Linker for CO2/CH4 Separation

“…MMMs consist of organic polymers and inorganic or inorganic–organic hybrid particles, which are embedded as functional fillers in the polymer matrix. A variety of materials impermeable and permeable have been used as filler materials. − …”

Increased Selectivity in CO2/CH4 Separation with Mixed‐Matrix Membranes of Polysulfone and Mixed‐MOFs MIL‐101(Cr) and ZIF‐8

“…Mixed‐matrix membranes (MMMs) are composite membranes made by combining an inorganic or inorganic‐organic hybrid material in the form of micro‐ or nanoparticles (discrete or dispersed phase) and a polymer matrix (continuous phase) (Scheme ) . By using two materials with different flux and selectivity, gas separation membranes combine synergistically the easy processability of polymers and the superior gas separation performance of inorganic materials.…”

“…Moreover porous inorganic fillers can overcome the trade‐off between selectivity and permeability which is typical for pure polymer membranes. Different types of inorganic additives, impermeable and permeable ones, have been used as filler materials , , …”

“…MOFs offer various advantages over zeolites and therefore are promising additives for MMMs . For example, MOFs can interact strongly with the polymer bulk material through ligands with a broad variety of functionalities so that the formation of micro gaps between inorganic and organic phase, which cause loss in selectivity, can be avoided . In order to obtain materials with optimized separation properties a perfect interaction between the two components is highly important for the preparation of MMMs.…”