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

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 (¹³C cross-polarization magic angle spinning), Fourier transform infrared spectroscopy, and elementary analysis. MP1 exhibited a high Brunauer-Emmett-Teller surface area (1020 m² g^-1), whereas the COOH-functionalized MP2 showed a much smaller surface area (150 m² g^-1) 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 CO₂ molecules, MP1 exhibited a high CO₂ adsorption capacity of 4.2 mmol g^-1 at 273 K, combined with an isosteric heat of adsorption (Q _st) of 29.6 kJ mol^-1. The COOH-functionalized MP2 showed higher Q _st of 34.2 kJ mol^-1 coupled with a modest CO₂ adsorption capacity of 2.2 mmol g^-1. Both network PIMs displayed high theoretical ideal adsorbed solution theory CO₂/N₂ 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 CO₂/N₂ selectivity values of 23 and 45, respectively. Besides the promising CO₂ capture and CO₂/N₂ 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^-1, respectively. Moreover, MP1 also demonstrated some potential for adsorptive separation of xylene isomers with adsorptive selectivity of 1.75 for m-xylene/o-xylene.