A novel COP adsorbent built up by thiophene group: Rapid and selective adsorption toward trace hazardous Hg(II)

• Published in: Separation and purification technology 2025-01, Vol.353, p.128482, Article 128482
• Main Authors: Zhu, Zhihong, Qin, Yuancheng, Liu, Siyu, Liu, Chao, Yan, Hewei, Ni, Cailing, Yang, Lixia
• Format: Article
• Language: English
• Subjects: Covalent organic polymers; Heavy metal hazards; Hg2; Mercury adsorption; Photothermal desorption
• ISSN: 1383-5866
• DOI: 10.1016/j.seppur.2024.128482

[Display omitted] •Thiophene-based covalent organic polymers (BTT-COPs) were directly synthesized via the Schiff base reaction.•Plenty of heteroatoms in BTT-COPs act as active sites to absorb Hg2+ ions.•Ultra-fast adsorption of trace Hg2+ at 1000 μg L−1 in the presence of 12 competing ions is achieved.•The photothermal capacity of BTT-COPs under irradiation, facilitate the rapid desorption of Hg2+.•BTT-COPs enables exceptional selectivity and recoverability for Hg2+. Mercury is one of the most toxic heavy metals to humans. Developing highly efficient adsorbent for removing mercury is of great significance. Herein, two thiophene-based COPs were synthesized through Schiff base reaction by rationally selecting thiophene group as COP building block and functional component simultaneously, avoiding the drawbacks of functionalization strategy such as sacrificing the porous structure and blocking the active sites. The high S/N content in the COPs structure enables robust adsorption towards Hg(II), with maximum adsorption capacity up to 468.8 mg g−1. Notably, even in the presence of 12 interfering ions, the resulting COP-BTTS effectively reduced trace Hg(II) at 1000 μg L−1 to 33 μg L−1 within 30 s, achieving a removal rate up to 97 %, and below the regulatory discharge limit of 10 μg L−1 for wastewater in 15 min. Moreover, the temperature of COP-BTTS can rise to 140 °C-150 °C under xenon light due to its exceptional photothermal property, which can facilitate the efficient desorption of Hg2+. And the COP-BTTS maintains its exceptional recoverability after the successive repeated 5 cycles. This work sheds light on the feasible strategy for designing and synthesizing COP adsorbent with high adsorption capacity, selectivity, and irradiation-assisted desorption of metal ions.