Facile surface amination strategy of PIM-1 based membranes for efficient CO2 capture

Carbon dioxide capture by membrane method is considered an important way to solve global warming, and it has become one of the most active research fields at present. Herein, a facile surface amination strategy by diazonium-induced anchoring process (DIAP) was introduced in the modification of polymers of intrinsic microporosity-1 (PIM-1) based membranes for efficient separation of CO2/N2. According to the detection of the chemical and surface properties, the polyaminophenylene (PAP) layer grafting on the surface could be regulated by simply changing the modification time. The modified membranes show significant increase in the CO2/N2 selectivity, which is attributed to the enhanced solubility-selectivity of the amino-rich surface. However, the attachment of the noncovalently grafted aniline groups increases the mass transfer resistance and surface non-uniformity, thereby significantly damaging the permeability of the membranes. Therefore, methanol is employed to clean the redundant PAP. As a result, the permeability of the membranes after methanol post-treatment increases evidently, while the membranes maintain good CO2/N2 selectivity. The selectivity of CO2/N2 and the permeability of CO2 are 34.1 and 11421.5 Barrer respectively at the optimal modification condition, which exceeds the upper bound established in 2019. This work will encourage the researchers to pay more attention to surface modification for CO2 capture, which might be relatively easy for industrial scale-up.