Microporous Polyimides with Uniform Pores for Adsorption and Separation of CO₂Gas and Organic Vapors

Three microporous polyimides, MPI-1, MPI-2, and MPI-3, with uniform pores were synthesized via one-pot polycondensation from tetrakis(4-aminophenyl)methane, tris(4-aminophenyl)amine and 1,3,5-tris(4-aminophenyl)benzene with pyromellitic dianhydride, respectively. The amorphous networks exhibit excellent thermal stability, large BET surface areas up to 1454 m 2 g –1, and narrow pore size distribution in the range from 5 to 6 Å. Their adsorption–desorption isotherms of CO 2 are reversible, and the CO 2 uptakes at 273 K and 1 bar are up to 16.8 wt %. Moreover, based on the ratios of initial slopes of isotherms, the CO 2 /N 2 and CO 2 /CH 4 separation factors are as high as 102 and 12, respectively. The above CO 2 adsorption and separation properties are attributed to the presence of abundant electron-rich heteroatoms in the polyimide networks and the unifrom ultralmicroporous structures. In addition, for MPI-1, the adsorption capacity of benzene vapor is 119.8 wt %, while the separation factors of benzene over nitrogen and water reach 342 and 28, respectively. The outstanding selective adsorptions of CO 2 gas and benzene vapor endow the microporous polyimides with promising potential in CO 2 capture and separation as well as air- and water-cleaning applications.