Synergistic dual-polymer blend membranes with molecularly mixed macrocyclic cavitands for efficient pre-combustion CO2 capture

Abstract

In this work, scalable polyphenylsulfone (PPSU) and polybenzimidazole (PBI) polymers were homogeneously blended to create an enhanced polymer matrix that could utilize both the higher permeability and mechanical flexibility of the former and the excellent selectivity and thermal stability of the latter. Within this blend matrix, calix[6]arene (CA6), an organic macrocyclic cavitand (OMC) with versatile solubility and high affinity for polymers, was also incorporated to further enhance the H2/CO2 selectivity using its polymer-intruded, partially open cavity that exhibits strong size-sieving nature. At 20 wt% CA6 loading, the nanocomposite blend membrane obtained a 103% higher H2/CO2 selectivity with an only mild permeability loss at 100 °C, which enabled both its overall pure- and mixed-gas separation performances to substantially surpass the Robeson upper bound. Most importantly, the ability of CA6 to molecularly mix with PPSU and PBI without phase segregation perfectly maintains the mechanical robustness of the pristine polymers, which is essential for potential industrial upscaling. This work presents exciting possibilities in designing molecularly mixed composite membranes (MMCMs) using synergistic polymer blends that offer clearly better scalability over the conventional phase-segregated mixed-matrix designs.