A novel bis(imino)pyridine-linked porous polymer having high BET surface area of 1580 m2 g-1 was synthesized through a condensation reaction between 2,6-pyridinedicarboxaldehyde and 1,3,5-tris(4-aminophenyl)benzene. The polymer (BIPLP-1) was post-synthetically functionalized with Cu(BF4)2 via coordination of copper cations to bis(imino)pyridine moieties, where BF4– ions act as charge balancing counter ions. We functionalized the polymer with Cu(BF4)2 since previous studies have shown that the functionalization of porous frameworks and porous molecular materials with fluorinated ions such as PF6–, TiF62–, and BF4– can result in enhanced CO2 uptake capacity. This is due to Lewis acid-base interactions between CO2 molecules and fluorinated ions, where CO2 acts as a Lewis acid and the fluorinated ion acts as a Lewis base. The functionalized polymer was characterized by different techniques such as BET, XPS, XRD, SEM, ICP, and IR. The complexation of the copper cations to bis(imino)pyridines of the polymer was confirmed by XPS studies. In addition, upon functionalization, significant decrease in surface area, pore size, and pore volume was observed, indicating the successful modification of the pores with Cu(BF4)2. Moreover, ICP studies shows that all bis(imino)pyridine moieties are coordinated to copper cations. The effect of functionalization on selective CO2 capture over N2 and CH4 was studied by collecting single-component adsorption isotherms for CO2, N2, and CH4 at 273 and 298 K. The isosteric heat of adsorption was calculated by the virial method, and the CO2/N2 and CO2/CH4 selectivities were estimated by initial slope method using the ratio of Henry’s law constants of single-component isotherms. Upon functionalization, the CO2 uptake capacity at 0.15 bar increased by 200%, and CO2/N2 and CO2/CH4 selectivity values increased by factors of up to 6. The functionalization resulted in a 19% enhancement in isosteric heat of adsorption for CO2. The functionalized network exhibits high CO2/N2 and CO2/CH4 selectivity values of 101 and 20, respectively.

Post-synthetic modification of a bis(imino)pyridine-linked porous polymer with inorganic fluorinated ions for highly selective CO2 capture

250th National Meeting (2015)

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