Synthesis, characterization and adsorption studies of a novel triptycene based hydroxyl azo-nanoporous polymer for environmental remediation

Gradual increase in CO₂ emission due to energy production from fossils fuels is a major contributor to global warming. Alternatively, "carbon free" nuclear energy generates radioactive and carcinogenic iodine vapors. Thus, the need to develop efficient sorbents for capture of CO₂ and I₂ is justified. Herein, we report a Triptycene-based-Hydroxyl-Azo-Polymer (TBHAP) derived from relatively inexpensive hydroquinone (one of the two monomers) and using water as a solvent. TBHAP is thermally stable and nanoporous with high surface area (SA_BET up to 824 m² g^-1). The presence of permanent porosity (due to triptycene), π-rich cavities (from abundant arene rings) and active functional groups [phenolic-OH and azo (-N=N-)] in the polymeric network of TBHAP makes it effective for reversible iodine (188 wt%), H₂ (8.9 mg g^-1: 77 K, 1âbar) and CO₂ (145 mg/g: 273 K, 1âbar) uptake with moderately high CO₂/N₂ selectivity (84 at 273 K). TBHAP is also an effective and selective adsorbent for toxic cationic dyes [Methylene blue (Q_m = 250 mg g^-1) and Rhodamine B (Q_m = 588 mg g^-1)] from an aqueous solution containing binary mixtures of cationic/anionic dyes. Thus, TBHAP is a versatile porous material with various applications in the domain of environmental remediation.