Wettability tunable conjugated microporous poly(aniline)s for long-term, rapid and ppb level sequestration of Hg(II)

Conjugated microporous poly(aniline)s (CMPAs) are an intriguing material platform for the selective capture of toxic heavy metal ions from water. However, the hydrophobic, monotonous N heteroatom and microporous properties limit their application scopes, particularly for the in-depth treatment requiring to a parts per billion (ppb) level. Herein, we report a novel chitosan-anchored CMPA (CMPA-CS), as designed through delicately exploiting the chitosan as either adsorption sites or pore templates for CMPA to acquire highly functionalized mesopores that could considerably facilitate Hg(II) adsorption. The CMPA-CS thus displayed excellently wide pH suitability (1.0–13.0), large capacity (862.1 mg g−1), ultrafast removal rate (k2 = 0.163 mg g−1 min−1), high affinity (Kd = 7.1 × 106), and strong anti-interference performance (selectivity of minimum 94.5% under the extreme influence of 100-fold-concentration cations). Besides, the Hg(II) concentration could be decreased from 0.578 ppm to less than 1.106 ppb in Minjiang river water substrates, below the EPR drinking water standards of 2 ppb. Comprehensive characterization revealed that the removal mechanism of Hg (II) was primarily a synergetic chelation reaction from the unique nitrogen ligands and O-containing groups, with the following features intensified: (i) good wettability to increase the interaction between CMPA and Hg(II) as contributed by the plentiful oxygen-containing groups; (ii) hierarchical mesopores that would promote ions transport efficiency as created by the chitosan. The new insight in this work can offer valuable guidelines for the design and structure optimization of CMPAs, facilitating its real-world commercial implementation.