Metal–Organic Frameworks Bearing Dense Alkyl Thiol for the Efficient Degradation and Concomitant Removal of Toxic Cr(VI)

Highly efficient removal of toxic Cr(VI) from aqueous media remains a crucial concern for ecosystem protection and public health. Herein, we demonstrated a new approach to solve this issue by constructing alkyl thiol-containing Zr-based metal-organic framework (MOF) adsorbents using simple and inexpensive mercaptosuccinic acid (MSA) and meso-dimercaptosuccinic acid (DMSA) as ligands. These chemically stable MOFs could be prepared in an uncomplicated, green, cost-effective, and scalable way. The interaction mechanism between alkyl thiol groups in MOFs and Cr(VI) was investigated in detail. Thanks to the formation of a Cr(VI)-thiolate complex and the oxidation of thiol groups, these designed MOFs not only exhibited high Cr(VI) adsorption capacities (202.0 and 138.7 mg/g for Zr-MSA and Zr-DMSA, respectively) but also displayed the immobilization ability for concomitant resultant Cr(III). Even in the presence of high concentrations of possibly coexistent interfering ions, the thiol-containing MOFs can still work effectively to decontaminate the Cr(VI) species. In addition, the strategy of introducing thiol groups into MOFs for Cr(VI) reduction and concomitant Cr(III) immobilization is universal for other MOFs, as verified by thiol-containing UiO-66 and MOF-808 prepared by a one-pot method. Therefore, our work not only produces several effective Cr(VI) adsorbents but also sets a general guideline for the construction of Cr(VI) adsorbents by introducing thiol groups into porous materials.