Regenerable Carbohydrazide-Linked Fluorescent Covalent Organic Frameworks for Ultrasensitive Detection and Removal of Mercury

Abstract

Mercury is one of the most toxic elements in the environment. Recently, a number of covalent organic frameworks (COFs) were developed for simultaneous detection and removal of mercury. They rely on post-synthetically modified sulfur-based ligands for irreversible mercury binding. In addition, their rigid structures resulted in low fluorescence yields. Herein, a novel highly luminescent COF named TFPPy-CHYD with a quantum yield of 13.6% was designed by integrating a pyrene-based building block with a flexible carbohydrazide linker. The nitrogen-based ligand allows reversible and highly selective binding of Hg2+. As a sensing platform, it has an ultralow detection limit of 17 nM mercury. More importantly, TFPPy-CHYD exhibits excellent performance in removing mercury from both air and water, providing very high Hg0 and Hg2+ adsorption capacities of 232 and 758 mg g–1, respectively. This work demonstrates enormous potential of luminescent COF for metal detection and remediation. By rational introducing metal ligands, a suite of new COF materials might be synthesized for the detection and removal of other metal ions.

A New Squaraine‐Linked Triazinyl‐Based Covalent Organic Frameworks: Preparation, Characterization and Application for Sensitive and Selective Determination of Fe3+ Cations

“…As we known, fluorescent COFs usually comprised by large π‐conjugated building units, such as porphin, pyrene, triphenylene, triazine, and phenyl or have large π‐conjugated system[3]. Heavy metal ions, such as Hg 2+ , Cu 2+ , Fe 3+ can be detected selectivity and sensitivity by fluorescent COFs with appropriate functional groups . Nitro explosive, such as nitrobenzene (NB), 4‐ nitrotoluene(4‐NT), 4‐nitrophenol (NP), 2,6‐dinitrotoluene (DNT), 2,4,6‐trinitrotoluene (TNT), 2,4,6‐trinitrophenylmethyl‐nitramine (Tetryl) and picric acid (PA) can also cause the strong fluorescence quenching of the fluorescent COFs .…”

Mercury Toxicity and Detection Using Chromo-Fluorogenic Chemosensors

“…Fluorescence quenching of 13 is attributed to a PET process from sensor to the Hg 2+ . Sensor 50 was applied for removing Hg 2+ from both air and water [ 44 ]. The microporous porphyrinic zirconium-based MOF 14 was developed by using meso-tetra(4-carboxyphenyl)porphyrin as a ligand for the detection of Hg 2+ in methanol medium [ 45 ].…”

Recent Progress in Functional Materials for Selective Detection and Removal of Mercury(II) Ions

“…Very recently, Qiu and co‐workers reported a regenerable and fluorescent carbohydrazide‐linked COF, namely, TFPPy‐CHYD, for the detection and removal of mercury from air and water sensitively. [ 68 ] Commercially available carbohydrazide (CHYD) and 1,3,6,8‐tetrakis(4‐formylphenyl)‐pyrene (TFPPy) were employed to obtain the target COF at low cost via a facile solvothermal route and without complicated postmodification (Figure 12B). The introduction of CHYD affected the π–π stacking in the COF skeleton and enhanced the luminescence of TFPPy‐CHYD, leading to a high quantum yield of 13.6%.…”