Boric Acid Functional Fluorescent Covalent–Organic Framework for Sensitive and Selective Visualization of CH₃Hg⁺

Abstract

Methylmercury (CH3Hg+) recognition remains a challenging and imperative task due to its high toxicity and wide existence in the ecosystem. Herein, a novel fluorescent covalent–organic framework containing a boric acid functional group (COF-BA) was prepared by a postmodification strategy for CH3Hg+ detection. COF-BA served as a sensing platform for CH3Hg+ with fluorescence static quenching accompanied by fluorescence color changing from intense blue to colorless, and the detection limit was determined as 1.68 μM in a relatively narrow concentration range. COF-BA also exhibited superior selectivity toward CH3Hg+ detection. Furthermore, the spiked and recovery test in real water samples showed its efficient detection practicality. The detection mechanism of COF-BA toward CH3Hg+ was investigated. The recognitive boric acid group in COF-BA was first replaced by CH3Hg+. Then, the quinoline structure that served to limit the rotation of the imine bond was disrupted, leading to dramatic fluorescence quenching. The boric acid functional COF fluorescent probe can be a promising sensing platform for the detection of methylmercury and also provides new ideas for the construction of new fluorescent COF materials.

The role of terminal coordinated amides in a series of Ca-tatb frameworks: pore size regulation and fluorescence sensing tunability

“…This result suggests that the 1D ordered pores and large specific surface area contribute significantly to the rapid diffusion effect. 38 Although the adsorption band of TNP (0.5 Â 10 À4 M) shows the maximal light absorption at UV light, it exhibits a broad extension into the blue region. Taking 2 as an example, the overlap between the adsorption of TNP and the FL spectra of the compound indicates the occurrence of efficient energy transfer from 2 to TNP, resulting in the fluorescence quenching of 2 in the presence of TNP molecules (Fig.…”

“…The experimental results are consistent with their pore structure analysis, further demonstrating that the larger pore size has a positive effect on their sensing performance. 38…”

Fluorescent covalent organic frameworks for environmental pollutant detection sensors and enrichment sorbents: a mini-review

“…Until now, no application of boron-containing fluorescent COFs as bifunctional platforms for detection and adsorption has been reported, and most reports have only explored their application as fluorescent probes for monitoring. For instance, in 2023, Xiao et al 21 have used a post-modification strategy to introduce (4-ethynylphenyl)boronic acid into the backbone of a fluorescent COF to synthesize a functionalized boron-containing COF (COF-BA) that emits intense blue fluorescence (Fig. 2E).…”

“…16–18 The other category comprises functionalized fluorescent COFs resulting from the introduction of fluorophores in the backbone or side chains. 19–21 Fluorescent COFs have several irreplaceable advantages, especially the adsorption performance, over general luminescent materials, mainly due to their highly developed pore structure, which can accommodate various types of targets via specific or non-specific chemical and non-bonded interactions. 22 Therefore, the development of fluorescent COFs with adsorption properties has attracted much attention.…”

Cycloadditions and Cyclization Reactions via Post-Synthetic Modification and/or One-Pot Methodologies for the Stabilization of Imine-Based Covalent Organic Frameworks

“…Povarov's reaction not only made it possible to obtain materials resistant to acidic, basic, or redox agents but also allowed the introduction of new functionalities into TPB-DMTP-COF that paved the way for the subsequent post-synthetic modification of the COF. As a result, a series of different quinoline-based materials QB-COF (Figure 1a) have been designed, synthesized according to Yaghi's conditions, and evaluated for different purposes, such as the capture and sensing of pesticides [28,29], cis-diol molecules [30], radioiodine [31], fluoride anion [32], and methylmercury [33], and their use as electrocatalysts for oxygen evolution [34,35] or for the fabrication of batteries [35,36]. This approach has been also used to convert other imine-based COFs into the corresponding quinoline-based derivatives.…”