Thiol functionalized covalent organic framework for highly selective enrichment and detection of mercury by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

A spherical thiol-functionalized covalent organic framework (COF-SH) was designedviaa facile thiol-yne click reaction of a alkynyl-terminated COF and pentaerythritol tetra(3-mercaptopropionate). The COF-SH was explored as a new adsorbent for the selective enrichment of Hg²⁺. The as-prepared COF-SH exhibited a uniform mesoporous structure, a high abundance of binding sites, and good chemical stability, which endow it with great performance for the adsorption of Hg²⁺and its corresponding maximum adsorption capacity was up to 617.3 mg g⁻¹. Furthermore, the adsorption behavior of Hg²⁺on the COF-SH wasin good agreement with the Langmuir and pseudo-second-order models. The influences of adsorbent dosage, pH, selectivity, and reusability of the COF-SH on Hg²⁺adsorption were also investigated. Besides this, the COF-SH showed high selectivity towards Hg²⁺even in the presence of a high concentration of K⁺, Na⁺, Ca²⁺, Mg²⁺and Zn²⁺metal ions. Using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS), the corresponding limit of detection (LOD) of Hg²⁺was determined at very low concentrations of 80 pg mL⁻¹(equal to 396 amoL μL⁻¹). In addition, the COF-SH was successfully applied to rapidly enrich and sensitively detect Hg²⁺in industrial sewage, with recoveries in the range of 101.8-103.4%, demonstrating the promising potential of COF-SH as an effective adsorbent for use in environmental sample pretreatment.