Mixed monomer derived porous aromatic frameworks with superior membrane performance for CO2 capture

Membrane separation has great potential for carbon dioxide capture, and materials play paramount important role in the membrane technology. In this paper, the mixed-monomer strategy is proposed for synthesis of a functional porous aromatic framework (PAF) named as PAF-45DPA. The monomer of diphenyl is employed for formation of the porous network and another monomer of diphenylamine is introduced to yield basic nitrogen sites. As a consequence, the prepared PAF-45DPA material possesses a surface area of 679 m2 g-1 with dominant pore size of ~0.58 nm which educes selective adsorption property toward carbon dioxide with IAST selectivity of 63.1 and CO2 uptake of ~45.3 cm3 g-1 at 298 K and 101 kPa measured from CO2 and N2 adsorptions. PAF-45DPA is subsequently used to fabricate hollow fiber membranes by hybridization with polysulfone (PSF) through the technique of dry jet-wet quench. Gas permeation analysis of CO2 and N2 reveals that the separation performance of PAF-45DPA/PSF is superior to those of PAF-45 and PDPA built from unary monomers. The PAF-45DPA/PSF membrane shows a dramatic improvement in the CO2/N2 separation factor (24.2) compared to PAF-45/PSF (15.4) and a significant enhancement in the CO2 permeance (72.6 GPU) compared to PDPA (51 GPU) at 298 K and 0.12 MPa. High stability of the PAF-45DPA/PSF membrane is also demonstrated together with its low cost and scale up production possibilities, which shed a light on advanced CO2 capture technology development for industrial gas exhausts.