Sorption-enhanced membrane materials for gas separation: a road less traveled

Solubility and diffusivity constitute two vertically tunable parameters for designing high-performance membrane materials for gas separation. The latter approach has received great attention, yielding a wealth of size-sieving materials reported in the literature. By contrast, this review highlights recent achievements of sorption-enhanced materials with superior gas separation performance, including fluorinated polymers for He/gas and gas/CH4 separations, and polar polymers and mixed-matrix materials comprising metalorganic frameworks for olefin/paraffin separations. The undervalued solubility and solubility selectivity are powerful tools in designing materials with superior separation properties and good resistance to plasticization caused by condensable components in the feed, which, otherwise, would decrease gas selectivity.