Pristine and Carboxyl-Functionalized Tetraphenylethylene-Based Ladder Networks for Gas Separation and Volatile Organic Vapor Adsorption.

A novel tetraphenylethylene-based ladder network (MP1) made by polycondensation reaction from 4,4',4″,4‴-(ethene-1,1,2,2-tetrayl)tetrakis(benzene-1,2-diol) and 2,3,5,6-tetrafluoroterephthalonitrile and its COOH-functionalized analogue (MP2) were synthesized for the first time. Their structures were confirmed by solid-state nuclear magnetic resonance (C cross-polarization magic angle spinning), Fourier transform infrared spectroscopy, and elementary analysis. MP1 exhibited a high Brunauer-Emmett-Teller surface area (1020 m g), whereas the COOH-functionalized MP2 showed a much smaller surface area (150 m g) but displayed a more uniform pore size distribution. Because of the high density of nitrile groups in the network polymers of intrinsic microporosity (PIMs) and strong interaction with quadrupole CO molecules, MP1 exhibited a high CO adsorption capacity of 4.2 mmol g at 273 K, combined with an isosteric heat of adsorption ( ) of 29.6 kJ mol. The COOH-functionalized MP2 showed higher of 34.2 kJ mol coupled with a modest CO adsorption capacity of 2.2 mmol g. Both network PIMs displayed high theoretical ideal adsorbed solution theory CO/N selectivities (51 and 94 at 273 K vs 34 and 84 at 298 K for MP1 and MP2, respectively). The high selectivities of MP1 and MP2 were confirmed by experimental column breakthrough experiments with CO/N selectivity values of 23 and 45, respectively. Besides the promising CO capture and CO/N selectivity properties, MP1 also demonstrated high sorption capacity for toxic volatile organic vapors. At 298 K and a relative pressure of 0.95, benzene and toluene sorption uptakes reached 765 and 1041 mg g, respectively. Moreover, MP1 also demonstrated some potential for adsorptive separation of xylene isomers with adsorptive selectivity of 1.75 for -xylene/-xylene.