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 designed via a 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.