Non-porous covalent organic polymers enable ultrafast removal of cationic dyes via carbonyl/hydroxyl-synergetic electrostatic adsorption.

[Display omitted] • An anionic covalent organic polymer (COP) with the so far fastest cationic dye adsorption kinetics is reported. • The adsorption mechanism is elucidated via comparative experiments and computer simulation. • The excellent performance is demonstrated to be attributed to 1 + 1 > 2 synergy between carbonyl and hydroxyl groups. • An automatic and recyclable water treatment device is constructed based on the anionic COP. • This work suggests that non-porous COPs can also be excellent adsorbents via the synergy of functional groups. Rapid and highly efficient removal of organic dyes from polluted water is of great significance for environmental protection and water resources management. Herein, an anionic covalent organic polymer (COP), denominated as COP OH+CO , with the fastest cationic dye adsorption kinetics so far was prepared and packed into solid phase extraction cartridges for rapid and automatic water treatment. As-prepared COP OH+CO contains abundant hydroxyl and carbonyl groups. Compared to COP OH and COP CO , other two COPs containing only hydroxyl and carbonyl, respectively, COP OH+CO gives a maximum adsorption capacity of 813 mg·g−1 towards cationic dye methylene blue (MB), which is about 4.6 times the sum of those of COP OH (42.4 mg·g−1) and COP CO (135 mg·g−1), suggesting the existence of 1 + 1 > 2 synergy between carbonyl and hydroxyl groups. Such a synergy is well demonstrated by theoretical calculation, which shows that the mutual penetration distance of electrostatic potentials in MB/COP OH+CO complex (4.722 Å) is much larger than those in MB/COP OH (0.443 Å) and MB/COP CO (1.602 Å). Although the rapid synthesis endows COP OH+CO with very poor porosity, the resulted surface adsorption avoids the long-term mass transfer, thus giving an ultra-fast adsorption kinetics with a so far fastest adsorption rate constant of 0.17 g·mg−1·s−1. This work demonstrates that by using the synergetic effect of surface functional groups, rapidly synthesized non-porous COPs may work as promising adsorbents for fast adsorption of targets. [ABSTRACT FROM AUTHOR]