School of Chemical and Biological Engineering, Lanzhou Jiaotong University, Lanzhou, 730070, China.
College of Chemistry and Chemical Engineering and State Key Laboratory of Applied Organic Chemistry, Lanzhou University, Lanzhou, 730000, China.
Dalton Trans. 2021 Feb 9;50(5):1874-1886. doi: 10.1039/d0dt04089d.
It is challenging to develop highly stable lanthanide luminescent sensors for detecting heavy metal ions and nitroaromatics in view of the human health and environmental security. To this end, two water stable Ln-MOFs with the chemical constitution of {[Ln(HL)]·3DMF·3H2O}n (Ln = Eu, LZG-Eu and Ln = Tb, LZG-Tb) have been developed solvothermally using a multidentate ligand (H4L) with the central phenyl backbone bisubstituted by 2,6-pyridine-dicarboxylic acid at the para-position, H4L = 1,4-bis(2',2'',6',6''-tetracarboxy-1,4':4,4''-pyridyl)benzene. Single crystal analysis demonstrates that two novel Ln-MOFs feature 4,4,4-connected nets with an unprecedented topology symbol of {42·6·83}2{42·62·82}{42·84} and contain two kinds of one-dimensional channels. Powder X-ray diffraction as well as the luminescence determination results indicate that they retain their crystallinity and structural integrity in harsh acidic and basic conditions with pH in the range of 4-11. Moreover, they are highly luminescent, which makes them excellent chemical sensors for detecting Cu2+ and 4-NP (4-nitrophenol) with high selectivity and sensitivity in aqueous media such as deionized water, tap water, and river water based on distinct quenching effects. To the best of our knowledge, their detection limits are lower than those documented so far. In addition, the quenching efficiency of 4-NP was retained in the presence of interfering ions even after the compounds were used for five cycles, which makes them attractive, reliable, visual, and recyclable luminescent Ln-MOF sensor materials for 4-NP. The recognition mechanism for Cu2+ could be attributed to the dissociation of the main framework induced by Cu2+ and the subsequent formation of a Cu2+ coordination species and that for 4-NP is considered to be multi-quenching mechanisms dominated by competition absorption.
开发用于检测重金属离子和硝基芳烃的高稳定性镧系元素发光传感器具有挑战性，这是出于对人类健康和环境安全的考虑。为此，我们采用具有中央苯环的多齿配体（H4L），以 2,6-吡啶二甲酸为对位取代基，合成了两种水稳定的 Ln-MOF，其化学式为{[Ln（HL）]·3DMF·3H2O}n（Ln = Eu，LZG-Eu 和 Ln = Tb，LZG-Tb）。单晶分析表明，这两种新型 Ln-MOF 具有 4,4,4-连接的网络，拓扑符号为{42·6·83}2{42·62·82}{42·84}，包含两种一维通道。粉末 X 射线衍射和发光测定结果表明，它们在 pH 值为 4-11 的苛刻酸性和碱性条件下仍保持结晶度和结构完整性。此外，它们具有很高的发光性，使其成为检测水溶液（如去离子水、自来水和河水）中 Cu2+和 4-NP（4-硝基苯酚）的优良化学传感器，具有高选择性和灵敏度，这主要归因于明显的猝灭效应。据我们所知，它们的检测限低于目前已报道的检测限。此外，即使在化合物经过五次循环使用后，存在干扰离子时，4-NP 的猝灭效率仍得以保留，这使得它们成为用于 4-NP 的有吸引力、可靠、可视化和可回收的镧系元素发光 MOF 传感器材料。Cu2+的识别机制归因于 Cu2+诱导的主框架的解离以及随后形成的 Cu2+配位物种，而 4-NP 被认为是由竞争吸收主导的多猝灭机制。
