Novel calixarene-based porous organic polymers with superfast removal rate and ultrahigh adsorption capacity for selective separation of cationic dyes

Exploring novel porous adsorbents for efficient water purification is a significant and urgent task. Two novel calixarene-based porous organic polymers (POPs) namely POP-8F and POP-10F were synthesized via a simple and mild reaction using octafluoronaphthalene and decafluorobiphenyl as the crosslinker. The Fourier transform infrared spectrometer, solid-state C-13 NMR spectra prove the successful construction of the POPs, and thermal gravimetric analyzer curves demonstrate the good thermal stabilities. Combining the advantages of porous structures, abundant adsorption sites and electronegative natures, both POP-8F and POP-10F exhibit extraordinary adsorption capacities and rates towards cationic dyes including Rhodamine B (RhB), methylene blue (MB) and crystal violet (CV). Especially for RhB, the removal efficiency can reach nearly 99 % within 4 min and the pseudo-second-order rate constant of POP-8F is 0.04386 g mg(-1) min(-1). Notably, the maximum adsorption capacity of POP-8F towards RhB is 2433 mg g(-1), surpassing all the previously reported porous adsorbents including covalent organic frameworks, metal organic frameworks, POPs, biomass adsorbents, activated carbons, etc. In addition, both POP-8F and POP-10F can selectively adsorb cationic dyes among the mixtures of cationic dyes and anionic dyes. More importantly, the calixarene-based POPs can efficiently remove cationic dyes through a simple column filtration and exhibit excellent reusability properties. All the above characteristics make POP-8F and POP-10F excellent porous adsorbents for water pollutant treatment and purification.