High porosity cyclotriphosphazene-based hyper-crosslinked polymers as efficient cationic dye MB adsorbents

• Published in: Polymer (Guilford) 2022-04, Vol.247, p.124787, Article 124787
• Main Authors: Xiong, Gang, Gao, Shan, Zhang, Qian, Ren, Baoyi, You, Lixin, Ding, Fu, He, Yongke, Sun, Yaguang
• Format: Article
• Language: English
• Subjects: Adsorption; Alkylation; Cationic dyes; Cationic polymerization; Crosslinking; Cyclotriphosphazene; Dimethyl acetals; Dye adsorption; Dyes; Exothermic reactions; Friedel-Crafts reaction; Hyper-crosslinked polymers; Methylene blue; Nanoparticles; Polymers; Porosity; Process parameters; Selectivity; Structural hierarchy
• ISSN: 0032-3861; 1873-2291
• DOI: 10.1016/j.polymer.2022.124787

Inspired by triptycene unit, the rigid paddle wheel compounds tris(o-phenylenedioxy)cyclotriphosphazene (TPP) and tris(2, 3-naphthalenedioxy)cyclotriphosphazene (TNP) were synthesized and employed as core building blocks to construct high porosity hyper-crosslinked polymers (HCP-TPP and HCP-TNP) via Friedel-Crafts alkylation reaction with formaldehyde dimethyl acetal (FDA). The bulk of HCP-TPP and HCP-TNP were comprised of nano-particles and exhibited hierarchical pore structures with remarkable high BET specific surface area of 1641.9 and 1700.2 m2 g−1, respectively. The adsorption capacities of HCP-TPP and HCP-TNP toward cationic dye methylene blue (MB) run up to 504.6 and 409.1 mg g−1 at 25 °C, respectively, but they hardly adsorbed anionic dye methyl orange (MO), exhibiting charge selectivity. The adsorption behaviors on MB were in consistence with the pseudo-second-order model and Langmuir model. The estimated thermodynamic parameters indicated the adsorption process was spontaneous and exothermic. Inspired by triptycene unit, the rigid paddle wheel compounds tris(o-phenylenedioxy)cyclotriphosphazene (TPP) and tris(2, 3-naphthalenedioxy)cyclotriphosphazene (TNP) were synthesized and employed as core building blocks to construct high porosity hyper-crosslinked polymers (HCP-TPP and HCP-TNP) via Friedel-Crafts alkylation reaction with formaldehyde dimethyl acetal (FDA). The bulk of HCP-TPP and HCP-TNP were comprised of nano-particles and exhibited hierarchical pore structures with remarkable high BET specific surface area of 1641.9 and 1700.2 m2 g−1, respectively. The adsorption capacities of HCP-TPP and HCP-TNP toward cationic dye methylene blue (MB) run up to 504.6 and 409.1 mg g−1 at 25 °C, respectively, but they hardly adsorbed anionic dye methyl orange (MO), exhibiting charge selectivity. The adsorption behaviors on MB were in consistence with the pseudo-second-order model and Langmuir model. The estimated thermodynamic parameters indicated the adsorption process was spontaneous and exothermic. [Display omitted] •Two novel cyclotriphosphazene-based hyper-crosslinked polymers were prepared from low cost raw materials.•They exhibited hierarchical structures with the highest BET specific surface areas among cyclotriphosphazene -based porous materials.•They charge-selectively absorbed cationic dye methylene blue (MB) with absorption capacities of 504.6 and 409.1 mg g−1 at 25 °C.