Cationic porous organic polymers for selective adsorption in gas and liquid phases

Abstract

Porous organic polymers are promising adsorbents due to their excellent stability, low density, and diverse functionalities. Currently, most research focuses on neutral porous organic polymers. However, these materials only adsorb guest molecules matching their pore dimensions due to the limitation of the cavity size, which restricts their application field. To address this issue, two cationic porous organic polymers (CTN-POPs, CTN-POP-1 and CTN-POP-2) were prepared from 1,1′-bis(2,4-dinitrophenyl)-4,4′-bipyridinium dichloride (1) with 5,10,15,20-tetra(4-aminophenyl)porphyrin (2) and 1,1,2,2-tetrakis(4-aminophenyl)ethene (3) via the Zincke reaction, respectively. N₂ adsorption experiments confirmed the porosity of CTN-POPs at 77 K. Furthermore, CTN-POPs displayed high CO₂/N₂ selectivity at 273 and 298 K, and the dynamic breakthrough experiment of CTN-POP-1 further verifies the dynamic separation performance for CO₂ and N₂ at 273 K. In the solution adsorption study, CTN-POP-1 exhibited higher adsorption capacity for anionic dyes and drugs owing to its porous structure and polycationic property. Moreover, the release ratios for dye-2 and drug-3 reached 96.9% and 99.3% in CTN-POP-1⊃dye-2 and CTN-POP-1⊃drug-3, respectively. Therefore, compared to neutral porous materials, CTN-POPs not only compensate for the traditional limitation of pore size-dependent adsorption performance but also expand the diversity of their application fields. Thus, this study provides an effective strategy for constructing functional materials to relieve the greenhouse effect, purify water resources, and promote drug delivery.