Metal-organic frameworks (MOFs) represent a class of highly ordered, crystalline hybrid materials formed through the self-assembly of metal ions or clusters and organic ligands. Their unique combination of high porosity, tunable pore size, large surface area, and structural versatility has positioned them as ideal candidates for advanced sensing applications. Among their most promising features is their inherent luminescence, arising from both inorganic nodes and organic linkers, which enables sensitive detection of various analytes. By incorporating luminescent guests—such as lanthanide ions, fluorescent dyes, quantum dots, and luminescent complexes—into MOF pores, researchers have developed multifunctional platforms capable of single- or dual-emission-based sensing with enhanced selectivity and sensitivity.
Lanthanide ions, particularly Eu³⁺ and Tb³⁺, are widely used due to their sharp emission peaks, long fluorescence lifetimes, and resistance to environmental interference. These properties stem from f-f transitions that are shielded within the 4f orbitals, minimizing quenching effects. However, direct excitation of lanthanides is inefficient due to forbidden transitions. To overcome this limitation, the “antenna effect” is employed: organic ligands absorb light and transfer energy efficiently to the lanthanide center.C2orf56 Antibody custom synthesis This mechanism allows for strong, stable luminescence upon integration into MOFs. For example, Eu³⁺-doped MIL-53-COOH(Al) exhibits selective fluorescence quenching in response to Fe³⁺, while Eu³⁺@UiO-66(DPA) shows high sensitivity toward Hg²⁺ in aqueous solutions. In some cases, transition metals like Ag⁺ or Cu²⁺ are introduced to act as recognition sites, enabling detection of analytes such as H₂S or glutathione through specific coordination interactions.
Fluorescent dyes, including rhodamine B and fluorescein derivatives, offer high photoluminescence quantum yields and broad emission spectra. However, their aggregation in solid states often leads to quenching. Encapsulating these dyes within MOF pores protects them from aggregation and enhances stability. Moreover, the host-guest interaction can be tuned to modulate emission intensity or wavelength. For instance, RhB@ZIF-8 shows distinct responses to nitroaromatic compounds and tetracycline antibiotics via quenching or enhancement mechanisms. Dual-emission sensors based on dye@MOF systems allow for ratiometric detection, where one emission serves as an internal reference, significantly improving accuracy by compensating for external fluctuations such as light source instability or concentration variations.
Quantum dots (QDs), especially semiconductor types like CdTe and ZnS, provide excellent photostability and narrow emission bands. When embedded in MOFs, they benefit from spatial confinement that prevents aggregation and enhances quantum yield. For example, ZnO@MOF-5 detects phosphate ions via fluorescence recovery after structural disruption caused by ion exchange. Similarly, PEG-ZnS QD@ZIF-67 offers ultrasensitive Cu²⁺ detection with low limits of detection. Ratiometric sensors combining QDs with MOFs enable real-time monitoring without calibration drift. A notable example is CdTe QDs@NH2-MIL-53(Al), which responds selectively to 6-mercaptopurine through internal filtering and passivation effects.
Carbon quantum dots (CQDs) have emerged as eco-friendly alternatives due to their low toxicity, biocompatibility, and tunable emission. They can be incorporated into MOFs either during synthesis or via post-functionalization. C-QDs@UiO-66-(COOH)₂ functions as a temperature sensor, showing reversible changes in emission intensity with temperature variation. In another system, amine-functionalized CQDs@UiO-66 detect 4-nitrophenol through fluorescence quenching.Fibrinogen γ Antibody Autophagy The ability to create dual-emission probes using CQDs and lanthanides enables visual, ratiometric sensing—ideal for field-deployable applications.PMID:34751953
Perovskite quantum dots (PeQDs), such as CsPbBr₃, exhibit outstanding optical properties but suffer from poor stability under ambient conditions. Encapsulation in MOFs like ZJU-28 or MOF-5 dramatically improves their durability and performance. CsPbBr₃@ZJU-28 demonstrates linear fluorescence response over a wide temperature range (20–160 °C), making it suitable for thermal sensing. Additionally, PeQDs@MOFs respond to metal ions and volatile organic compounds, expanding their utility beyond temperature detection.
Finally, luminescent complexes such as Ru(bpy)₃²⁺ and Ir(ppy)₂(bpy)⁺ are integrated into MOFs to achieve white-light emission or targeted sensing. These complexes offer high brightness and tunable emission. Ru(bpy)₃²⁺@MIL-101(Al)-NH₂ acts as a ratiometric water sensor, while MnO₂ nanosheet-coated Ru(bpy)₃²⁺-UiO-66 detects glutathione in cancer cells with high precision. Such systems demonstrate the potential of MOF-based composites in biomedical diagnostics and environmental monitoring.
In summary, the encapsulation of diverse luminescent guests into MOFs enables the development of versatile, highly sensitive chemical sensors. Each guest type brings unique advantages—lanthanides for long-lived emission, dyes for colorimetric response, QDs for stability, CQDs for biocompatibility, PeQDs for tunable optics, and complexes for multicolor output. Future advancements will focus on enhancing water stability, reducing toxicity, and integrating machine learning for data interpretation. As research progresses, these smart MOF-based sensors are poised to revolutionize fields ranging from healthcare to environmental safety.MedChemExpress (MCE) offers a wide range of high-quality research chemicals and biochemicals (novel life-science reagents, reference compounds and natural compounds) for scientific use. We have professionally experienced and friendly staff to meet your needs. We are a competent and trustworthy partner for your research and scientific projects.Related websites: https://www.medchemexpress.com