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.