A Stable Cd(II)-Based Metal–Organic Framework: Synthesis, Structure, and Its Eu³⁺ Functionalization for Ratiometric Sensing on the Biomarker 2-(2-Methoxyethoxy) Acetic Acid

Abstract

A novel two-dimensional Cd-based metal–organic framework (MOF), [Cd­(pddb)­H2O] n (Cd-MOF), has been hydrothermally synthesized using the V-shaped ligand 4,4′-(pyridine-2,6-diyl)-dibenzoic acid (H2pddb) and structurally characterized. The framework exhibits fascinating one-dimensional in-plane channels functionalized with active pyridine-N sites. The as-synthesized Cd-MOF exhibits excellent water and chemical stability. Furthermore, a simple and nondestructive coordinated postsynthetic modification method has been applied to Cd-MOF to obtain a class of MOF hybrids functionalized by lanthanide ions. More interestingly, Eu3+@Cd-MOF can act as a dual-emissive ratiometric fluorescent probe for 2-(2-methoxyethoxy) acetic acid (MEAA), a metabolite of 2-(2-methoxyethoxy) ethanol, which could result in DNA damage and teratogenic and developmental toxicity. During the sensing process, the fluorescence sensor exhibits notable water tolerance, reusability, and a low detection limit (8.5 μg mL–1). In addition, the chemical substances in human urine and serum do not interfere with the fluorescence quenching process, which makes it possible for the fluorescent probe to be applied in the detection of MEAA in human urine and serum systems. The possible sensing mechanism is also studied and discussed in detail.

Fabrication of a Stable Europium-Based Luminescent Sensor for Fast Detection of Urinary 1-Hydroxypyrene Constructed from a Tetracarboxylate Ligand

“…Besides, an obvious shift of the maximum excitation peak in the excitation spectra of compound 1 was discovered with the concentrations of 1-HP increasing, proving that no static quenching process is presented in the sensing process of 1-HP (Figure S10). , To further comprehensively explore the quenching mechanism of compound 1 toward 1-HP, the UV–vis spectra of compound 1 , the ligand H 4 ddpp, 1-HP, and other urine species were recorded (Figure S11). Compared with the UV–vis spectra of other urine species, the UV–vis absorption spectrum of 1-HP shows a strong absorption band between 250 and 400 nm, which presents a large extent of overlap with the absorption spectra of H 4 ddpp and compound 1 .…”

“…Therefore, the competitive energy absorption may be a probable explanation for such luminescence quenching behavior of 1 toward 1-HP. The energy adsorbed by H 4 ddpp can be partly captured by 1-HP, giving rise to the reduction of the efficiency of ligand-to-metal energy transformation (LMET), accompanied by the occurrence of the quick luminescence quenching effect. − As discussed above, the dual function of the dynamic quenching and competitive energy absorption can be interpreted by the extraordinary luminescent quenching phenomenon of compound 1 toward 1-HP.…”

Engineering of Metal–Organic Frameworks as Ratiometric Sensors

“…Among them, Eu 3+ @Cd-MOF showed a dual-emissive ratiometric fluorescent sensor for 2-(2-methoxyethoxy) acetic acid, a metabolite of 2-(2-methoxyethoxy) ethanol. 204 The fluorescence intensity of the 5 D 0 → 7 F 2 transitions of Eu 3+ at 616 nm was reduced, when MEAA was added to the suspensions of Eu 3+ @Cd-MOF, but at the same time the fluorescence intensity of the ligands at 418 nm steadily increased, indicating that Eu 3+ @Cd-MOF acts as a dual-emissive ratiometric fluorescent probe for MEAA. Furthermore, the detection ability of Eu 3+ @Cd-MOF for MEAA remains undisturbed in the presence of different chemical components in human urine and serum (Figure 70).…”

A new three-dimensional zinc(ii) metal–organic framework as a fluorescence sensor for sensing the biomarker 3-nitrotyrosine

“…Their applications include photoelectrochemical processes, drug delivery, luminescence sensing, heterogeneous catalysis, wastewater treatment, gas storage and separation, etc. [22][23][24][25][26][27][28][29][30][31][32][33][34][35] Among the many well-designed MOFs, luminescent MOFs (LMOFs) are becoming an effective sensing material and attracting more and more attention because of their outstanding luminescence stability, excellent selectivity, environmental adaptability and low cost. [36][37][38] To date, LMOFs have been studied for detecting anions, cations, gas, explosives, pesticides, anti-biotics and biomarkers.…”