Synergistic disulfide sites of tetrathiafulvalene-based metal-organic framework for highly efficient and selective mercury capture

Currently, most reported Hg2+ adsorbents basically depend on their thiol or S-containing heterocyclic structure such as thiophene sites. However, the thiol site in adsorbents has strong affinity towards Hg(2+ )but low anti-oxidation behavior while the latter one possesses relative weak Hg2+ affinity but strong chemical stability. In this work, the tetrathiafulvalene-functionalized adsorbent with synergistic disulfide sites which have both high Hg2+ affinity and excellent chemical stability was proposed for highly efficient Hg2+ capture. As a proof-of-concept experiment, a new soft-base electron-donor tetrathiafulvalene-functionalized Zr(IV)-based metal--organic frameworks (MOFs) was designed and constructed. The prepared Zr-TTFTB exhibited high porosity, high stability and highly affinitive active sites. As expected, Zr-TTFTB showed remarkable Hg2+ adsorption capacity of 962 mg g(-1), which surpassed all the reported adsorbents with S-containing heterocyclic site. More significantly, Zr-TTFTB demonstrated a superhigh distribution coefficient value (K-d) of 1.15 x 10(8) mL g(-1) to-ward Hg2+ adsorption, which allowed it to fast decrease the Hg2+ concentration to below 0.88 ppb, well less than the drinking water standard. Meanwhile, Zr-TTFTB possessed the outstanding renewable performance in adsorption-regeneration cycles. A combination of experimental results and theoretical calculation revealed that the strong binding ability and impressive Hg2+ capture performance of Zr-TTFTB were attributed to densely populated synergistic disulfide sites. This work not only provides the synergistic disulfide sites strategy for preparing the high-performance Hg2+ adsorbent, but also discovers the exceptional potential of tetrathiafulvalene-functionalized Zr(IV)-based MOF for environmental remediation.