Mixed matrix membranes derived from nanoscale porous organic frameworks for permeable and selective CO2 separation

Membrane separation has great potential for carbon dioxide capture. We have been developing porous organic frameworks (POFs) as a new class of nanofillers for mixed matrix membranes fabrication. A triangle monomer of melamine (MA) reacts with another linear monomer of 1, 4-piperazinedicarboxaldehyde (PDA) in a microwave system to form the POF material (designated as MAPDA). As-synthesized MAPDA possesses an open framework featured with high surface area of 548.3 m2 g−1 and a large pore of ~1.0 nm. SEM shows that MAPDA particles are in size of ~42 nm, and adsorption measurement reveals that MAPDA is favorable for adsorbing CO2 with an uptake of 47.0 cm3 g−1 at 298 K and 101 kPa. Mixed matrix membranes of MAPDA/PIM-1 with different MAPDA loadings (0–20 wt%) are produced by blending nanofillers of MAPDA and soluble matrices of PIM-1. Single gas permeations demonstrate that CO2 permeability is increased dramatically from 3694.5 to 7861.9 Barrer, meanwhile the CO2/N2 selectivity is enhanced from 18.9 to 23.9 for pure PIM-1 and for a representative membrane of MAPDA/PIM-1 with 15 wt% MAPDA. High porosity and molecular affinity make the predominant contribution to the enhancements of CO2 permeability and CO2/N2 selectivity. MAPDA/PIM-1 membranes are also very selective for capturing CO2 from gas mixtures of 50CO2:50N2 and 15CO2:85N2 with separation performances exceeding the latest upper bound. The good separation property and the high stability of MAPDA/PIM-1 have shed a light on next-generation membrane for CO2 separation development.