A high-temperature resistant benzimidazole-based porous polymer for efficient adsorption of trinitrotoluene in aqueous solution

A novel benzimidazole-based porous polymer, denoted as PTBI, was synthesized utilizing self-synthesized 1,3,5-tris(1H-benzo[d]imidazol-2-yl)benzene (TBI) and 4,4′-difluorobenzophenone as primary materials via a CN coupling reaction, followed by a freeze-drying process. PTBI displayed commendable thermal stability, as evidenced by a temperature of 475°C at which a 5% weight loss occurred and a char yield of up to 65% at 800°C. Trinitrotoluene (TNT) was effectively adsorbed by PTBI in aqueous solutions, thanks to the combined effects of three π–π interactions and one dipole–π interaction. At 25°C, PTBI achieved a maximum adsorption capacity as high as 280.8 mg/g, with approximately 60% of this capacity attained within just 1 h. Furthermore, a thermodynamic analysis showed that the adsorption of TNT by PTBI was a spontaneous, exothermic process that was followed by a decrease in entropy. It is noteworthy that following five adsorption and desorption cycles, the adsorption efficiency held steady at a relatively high level using acetone as the eluent. These promising results underscore PTBI's significant potential in the realm of TNT wastewater treatment, positioning it as a compelling candidate for further research and application under extreme condition in this field.