Highly porous polysalicylates via Grignard reagent triggered “three-in-one” polyesterification and their high-loading nanocomposite membranes for gas separation

Porous organic polymers (POPs) with flexible linkers demonstrated some very unique properties, although the challenge remains to get high surface area. Herein, an efficient access to highly porous polysalicylates (named Mg@BIT-POP-60 and Mg@BIT-POP-61) with benzylic (sp³ C) ester linkage was developed by a powerful “three-in-one” strategy aided by Grignard reagent. That is, three events of (i) deprotonation of benzylic (sp³) alcohol, (ii) activation of salicylate chemical switch for efficient polyesterification by Grignard reagents, and (iii) monolith loading of Mg²⁺ in the polymer happened simultaneously by only one simple operation, which lead to flexible polysalicylates with high BET surface area up to 549 m² g⁻¹. In addition, an easy processing technology named premixing-hot pressing (pm-HoP) was developed to make the nanocomposite membranes with high loadings of Mg@BIT-POP-61 (50 wt%) in polycaprolactone (PCL). The reversed H₂/CO₂ selectivity of 3.12 favoring H₂ was observed comparing with pristine PCL (0.3), as well as high H₂ permeability of 5805 Barrer. This is a promising strategy to develop porous fillers-based nanocomposite membranes for overcoming trade-off effect in gas separation technology.