Ratiometric Luminescent Thermometer Research Articles

Highly Sensitive Solid Ratiometric Luminescent Thermometer Based on N,C-Chelating Four-Coordinate Organoboron Compounds.

Realizing ratiometric thermometers using single-component organic solid-state luminophores is attractive but challenging. Here, we synthesized a series of N,C-chelated tetra-coordinated organoboron compounds and characterized their structures. Among them, sample BN2Br can be used as a luminescent thermometer and exhibits a high temperature sensitivity (3.67% K-1), a wide response range of 120-280 K, and good reversibility, which is mainly due to the temperature-dependent intermolecular stacking effect in the solid state. The proposed ratiometric thermometry protocol may provide new insights for developing photonic thermometers.

Novel Type of Non‐Toxic, Degradable, Luminescent Ratiometric Thermometers Based on Dyes Embedded in Disulfide‐Bridged Periodic Mesoporous Organosilica Particles

AbstractDespite the excellent thermometric performance of many developed luminescent nanomaterials, their use has not gone beyond proof‐of‐concept in vivo experiments to date. An important issue that needs to be resolved before moving toward true biomedical applications of engineered nanothermometers is their potential toxicity and bioaccumulation in the human body considering the ultimate objective of clinical applications. Since most reported nanothermometers currently are not degradable materials and are mainly based on the incorporation of heavy metal ions, these aspects remain of genuine concern in the fields of nanomedicine, nanobiotechnology, nanotoxicology, and nanopharmacology. This work explores the possibility of designing visible, as well as near‐infrared, emitting luminescent ratiometric nanothermometers based on appropriate organic dye mixtures embedded in hollow disulfide‐bridged periodic mesoporous organosilica (PMO) particles. Such hybrid particles show excellent thermometric performance in the physiological temperature range (20–50 °C), favorable degradability in simulated physiological conditions, as well as no toxicity to healthy normal human dermal fibroblast (NHDF) cells in a wide concentration range. Considering the simplicity of the approach from the synthetic point of view, and the large available library of known fluorescent dyes emitting in various regions of the electromagnetic range, this motif renders a very promising approach to designing novel non‐toxic, decomposable, luminescent ratiometric thermometers.

Regulating thermometric properties of single-band ratiometric luminescent thermometers based on Eu3+-activated Y2W3O12·3H2O nanoparticles via controlling doping content and excitation model

Series of Eu3+-activated Y2W3O12·3H2O nanoparticles were designed to realize high-sensitive optical thermometry. The resultant nanoparticles can emit bright visible emission from Eu3+ upon the excitation of 296 nm (charge-transfer state (CTS) of O2- → W6+), 394 nm (ground state absorption (GSA)) and 536 nm (excitation state absorption (ESA)), of which the fluorescence intensities were influenced by dopant content. The negative thermal expansion properties of studied nanoparticles were clarified via temperature-dependent X-ray diffraction patterns. Moreover, the thermal quenching behaviors of final products were also investigated through temperature-related emission spectra. Specifically, upon the CTS and GSA processes, the developed nanoparticles underwent significant thermal quenching effect, whereas the thermally enhanced luminescence was observed under ESA process. Herein, through using the single-band ratiometric (SBR) method to investigate the fluorescence intensity ratio of the red emission from 5D0 → 7F2 transition of Eu3+ at high temperature, the thermometric properties of prepared nanoparticles were studied. It was found that maximum absolute and relative sensitivities of Eu3+-activated Y2W3O12·3H2O nanoparticles reached up to 0.061 and 4.944 % K−1, respectively, and they can be regulated by changing Eu3+ dopant and SBR models (i.e., ESA+CTS and ESA+GSA combinations), realizing high-sensitive optical thermometry. Our findings may provide some guidelines for manipulating the thermometric properties of rare-earth ions activated materials and developing new SBR luminescence thermometers.

Triple-Decker Hexaazamacrocyclic Lanthanide(III) Complexes: Structure, Magnetic Properties, and Temperature-Dependent Luminescence.

The reaction of fluoride anions with mononuclear rare-earth(III) complexes of the hexaazamacrocycle derived from 2,6-diformylpyridine and ethylenediamine affords trinuclear coordination compounds [Ln3L3(μ2-F)4(NO3)2](NO3)3. The X-ray crystal structures of these complexes show triplex cationic complexes where the three roughly parallel macrocyclic lanthanide(III) units are linked by bis-μ2-F bridges. The detailed analysis of the photophysical properties of the [Eu3L3(μ2-F)4(NO3)2](NO3)3·2H2O and [Tb3L3(μ2-F)4(NO3)2](NO3)3·3H2O complexes reveals different temperature dependence of luminescence intensity and luminescence decay time of the Eu(III) and Tb(III) derivatives. The spectra of mixed species of average composition [Eu1.5Tb1.5L3(μ2-F)4(NO3)2](NO3)3·3H2O are in accordance with the ratiometric luminescent thermometer behavior. Measurements of the direct-current (dc) magnetic susceptibility of the [Dy3L3(μ2-F)4(NO3)2](NO3)3·2H2O complex indicate possible ferromagnetic interactions between the Dy(III) ions. Alternating current (ac) susceptibility measurements of this complex indicate single-molecule magnet behavior in zero dc field with magnetic relaxation dominated by Orbach mechanism and an effective energy barrier Ueff = 12.3 cm-1 (17.7 K) with a pre-exponential relaxation time, τ0 of 7.3 × 10-6 s. A similar reaction of mononuclear macrocyclic complexes with a higher number of fluoride equivalents results in polymeric {[Ln3L3(μ2-F)5](NO3)4}n complexes. The X-ray crystal structure of the Nd(III) derivative of this type shows trinuclear units that are additionally linked by single fluoride bridges to form a linear coordination polymer.

A novel Y/Eu co-doped Ln-MOF for ratiometric luminescent thermometer of high sensitivity

Lanthanide metal-organic frameworks (Ln-MOFs) co-doped by mixed lanthanide ions is a preeminent candidate for ratiometric luminescence thermometers. In recent years, there are few studies on the synthesis of such MOFs by introducing Ln3+ ions of no luminescent properties such as Y3+. Herein, a novel Y/Eu co-doped Ln-MOF (Y0.95Eu0.05NDPA, H4NDPA = 5,5′-naphthalene-1,4-diyl-diisophthalic acid) was synthesized via solvothermal methods, which showed good phase purity and thermal stability. Compared with EuNDPA, the Y3+ ions in Y0.95Eu0.05NDPA dilute the molar concentration of Eu3+, causing the emerge of ligand emission band. The luminescence intensity ratio of organic ligands and Eu3+ owns a good exponential dependence on temperature variation. As investigated, Y0.95Eu0.05NDPA owns the merits including a wide temperature sensing range (303–423 K), high relative sensitivity (3.04 %·K-1 at 423 K), good spectral repeatability (>92 %) and distinct emission color change from red to blue. This novel Y0.95Eu0.05NDPA ratiometric thermometer is expected to promote the application and development of dual-emission MOF materials in the field of microelectronic temperature measurement.

Interfacial compatible PolyMOF membranes as ratiometric fluorescence temperature sensors

Cryogenic temperature sensors play significant roles in manufacturing, metallurgy, and aerospace. Metal-organic frameworks (MOFs) as emerging crystal materials exhibited inherent advantages as fluorescence temperature sensors and researchers have shifted their focus toward incorporating MOFs materials into mixed matrix membranes (MMMs) for broader practical applications. However, the poor interfacial compatibility between MOFs particles and the polymer matrix would cause aggregation-induced fluorescence quenching and reduced energy transfer efficiency, thereby compromising temperature sensing performances. Herein, we adopt a post-synthetic copolymerization strategy to realize an interfacial-compatible membranous ratiometric luminescent thermometer based on the emissions of ligands and lanthanide ions. Benefiting from the controllable covalent cross-linking structures, the designed polyMOF membrane exhibited excellent interfacial compatibility and avoided MOFs irregular morphology agglomeration and phase separation, which contributed to outstanding fluorescence temperature sensing performance with excellent sensitivity ranging from 0.300 to 0.745 %·K−1 within the temperature range of 80–300 K, superior to recent reported MOFs-based thermometers. This research presents a promising approach for the design and fabrication of interfacial compatible MOFs-based membranes with excellent fluorescence temperature sensing properties, advancing the understanding of structure-property relationships and accelerating the practical applications.

Luminescent Ln3+-based silsesquioxanes with a β-diketonate antenna ligand: toward the design of efficient temperature sensors.

We report the synthesis and single-crystal X-ray diffraction, magnetic, and luminescence measurements of a novel family of luminescent cage-like tetranuclear silsesquioxanes (PhSiO1.5)8(LnO1.5)4(O)(C5H8O2)6(EtOH)2(CH3CN)2⋅2CH3CN (where Ln = Tb, 1; Tb/Eu, 2; and Gd, 3), featuring seven-coordinated lanthanide ions arranged in a one-capped trigonal prism geometry. Compounds 1 and 2 exhibit characteristic Tb3+ and Tb3+/Eu3+-related emissions, respectively, sensitized by the chelating antenna acetylacetonate (acac) ligands upon excitation in the UV and visible spectral regions. Compound 3 is used to assess the energies of the triplet states of the acac ligand. For compound 1, theoretical calculations on the intramolecular energy transfer and multiphonon rates indicate a thermal balance between the 5D4 Stark components, while the mixed Tb3+/Eu3+ analog 2, with a Tb:Eu ratio of 3:1, showcases intra-cluster Tb3+-to-Eu3+ energy transfer, calculated theoretically as a function of temperature. By utilizing the intensity ratio between the 5D4→7F5 (Tb3+) and 5D0→7F2 (Eu3+) transitions in the range 11-373K, we demonstrate the realization of a ratiometric luminescent thermometer with compound 2, operating in the range 11-373K with a maximum relative sensitivity of 2.0% K-1 at 373K. These findings highlight the potential of cage-like silsesquioxanes as versatile materials for optical sensing-enabled applications.

Red- and NIR-emitting lanthanide complexes for photo- and electroluminescent nanothermometry in the cryogenic and high-temperature range

Ratiometric luminescent thermometers, particularly lanthanide-based, become very important, and long wavelength range is of particular interest due to low signal scattering. With this in mind, a series of new red and NIR emitting lanthanide Schiff base complexes were synthesized and characterized in detail for use as components of luminescent thermometers. Red-emitting europium complexes demonstrated high temperature sensitivity (up to 7 %/K) in the cryogenic temperature range (80–200 K), where the ligand-to-europium luminescence intensity ratio (LIR) was used as a signal. In contrast, NIR emitting ytterbium complexes demonstrated no sensitivity in the cryogenic range; however, their luminescence was sensitive to high temperatures (300–600 K), which is currently of particular interest. Ytterbium and europium complexes were also tested in OLEDs, and due to high temperature sensitivity, europium complexes were used for the first electroluminescent thermometers.

A ratiometric luminescence thermometer based on lanthanide encapsulated complexes.

Lanthanide-containing complexes have been widely developed as ratiometric luminescence thermometers, which are non-invasive, contactless and accurate. The synthesis of these Ln complexes generally requires high temperatures, multiple steps and other harsh conditions. Moreover, bimetallic lanthanide complexes, which have been reported to be better thermometers, are even more challenging to synthesize. This complexity can be simplified by preparing a host-guest complex of lanthanides. In this work, Tb or both Tb and Eu are encapsulated in an MOF host, making them emissive. The ratio of Tb/Eu was also easily tuned by simply changing their ratio in the solution, resulting in a tunable emission. Accordingly, we were able to synthesise both the emissive Tb complex and Tb/Eu complexes at different ratios using a single host. The complexes were found to be suitable as ratiometric luminescent thermometers in the temperature range of 160-380 K, with reasonably good sensitivity and uncertainty. The thermometer's sensitivity and uncertainty were significantly improved using bimetallic Tb and Eu host-guest complexes. Calculations using the host and Eu emission ratio were found to provide better thermometer parameters than the commonly reported Tb and Eu emission ratio. Thus, using a single host, we were able to synthesise different lanthanide complexes that can sense temperature, and we improved the thermometer parameters by incorporating multiple lanthanides in a single host. This research will enable the scientific community to reexamine the applicability of unexplored host-guest lanthanide complexes.

Intensity and lifetime ratiometric luminescent thermometer based on a Tb(III) coordination polymer.

A three-dimensional terbium(III) coordination polymer of formula [Tb(bttb)0.5(2,5-pzdc)0.5]n (1) [H4bttb = 1,2,4,5-tetrakis(4'-carboxyphenyl)benzene and H2-2,5-pzdc = 2,5-pyrazinedicarboxylic acid] was obtained under hydrothermal conditions. The bttb4- tetraanion in 1 adopts the bridging and chelating-bridging pseudo-oxo coordination modes while the 2,5-pzdc2- dianion exhibits a rather unusual bis-bidentate bridging pseudo-oxo coordination mode, both ligands being responsible for the stiffness of the resulting 3D structure. Solid-state photoluminescent measurements illustrate that 1 exhibits remarkable green luminescence emission, the most intense band occurring in the region of 550 nm (5D4 → 7F5) with lifetimes at the millisecond scale. Thermometric performances of 1 reveal a maximum relative sensitivity (Sm) of 0.76% K-1 at 295 K (δT = 0.05 K), constituting a TbIII ratiometric solid luminescent thermometer over the physiological temperature range. Variable-temperature static (dc) magnetic susceptibility measurements for 1 in the temperature range 2.0-300 K show the expected behavior for the depopulation of the splitted mJ levels of the 7F7 ground state of the magnetically anisotropic terbium(III) ion plus a weak antiferromagnetic interaction through the carboxylate bridges. No significant out-of-phase magnetic susceptibility signals were observed for 1 in the temperature range 2.0-10.0 K, either in the absence or presence of a static dc magnetic field.

Dye@ZIF-8 as dual-emission luminescence temperature sensors

Improving ZIF-8 temperature sensitivity has important significance by adjusting the channel properties. In this work, a series of efficient and stable dual-wavelength composites sensors are obtained by encapsulating organic fluorescent dyes (rhodamine B (RhB), fluorescein (FL), rhodamine 6 G (R6G) and acriflavine (Acf)) into ZIF-8, which are named as RhB@ZIF-8, FL@ZIF-8, R6G@ZIF-8, Acf@ZIF-8, respectively. The composites are characterized by powder X-ray diffraction (PXRD), fourier transform infrared (FTIR), thermogravimetry (TGA) and luminescent measurements. The composites of Dye@ZIF-8 exhibit exceptional characteristics, including high stability, reusability, and high yield, and effectively overcome the inherent issue of dye quenching due to aggregation in solid materials. In the temperature sensitivity tests, the relative sensitivity range of R6G@ZIF-8 is 1.618–4.583 % °C−1 (temperature range of 70–110 °C). This paper provides an idea to develop ratiometric luminescent thermometers by elaborately combining the host and guest units, which is very conducive to a large number of repetitions and research in the future.

A Doped Lanthanide-Based Coordination Polymer Exhibiting High Relative Sensitivity to Ratiometric Luminescent Thermometers at 440 K.

Ratiometric luminescent thermometers with excellent performance often require the luminescent materials to possess high thermal stability and relative sensitivity (Sr). However, such luminescent materials are very rare, especially in physiological (298-323 K) and high-temperature (>373 K) regions. Here we report the synthesis and luminescent property of [Tb0.995Eu0.005(pfbz)2(phen)Cl] (3), which not only exhibits high Sr in physiological temperature but also has a Sr up to 7.47% K-1 at 440 K, the largest Sr at 440 K in known lanthanide-based coordination compound luminescent materials.

Bimetallic Eu/Tb Complexes for Ratiometric Temperature Sensing with Unusual Enhancement of Eu Luminescence with Temperature

In this paper we describe the results of the influence of temperature in the range of 280–340 K on the luminescence of bimetallic Eu/Tb complexes with N-heterocyclic ligand L based on 2,2′-bipyridyldicarboxylic acid in acetonitrile. The experiments were carried out for systems with various Eu/Tb ratios. The stability of the complexes of the ligand L with metal M (Eu or Tb) was determined using spectrophotometric titration in acetonitrile solutions. The LM complexes’ stability constants were found to be typical for these systems; however, the stability of Eu complex is slightly higher than that for Tb. Along with rising temperature, we observed a decrease in Tb emission intensity and, at the same time, an enhancement in Eu luminescence. An explanation of Eu luminescence enhancement involves the appearance of charge transfer states, bands of which can be observed in the Eu luminescence excitation spectra as difference spectra measured with two close temperatures. The unusual Eu luminescence enhancement upon heating was observed for the first time for the complex with tetradentate O,N-type heterocyclic diamide ligand L, while an inverse phenomenon was observed with the Tb luminescence. The Eu luminescence enhancement was found earlier for various carboxylate complex salts, but not for heterocyclic coordination complexes. This allows the construction of a ratiometric luminescent thermometer in the range of 280–340 K using the ratio of luminescence intensities for Eu and Tb. The stability constants for the individual Eu and Tb complexes help us to understand the equilibrium in L:Tb:Eu complex system and shed light on plausible speciation in solution.

Ratiometric luminescent thermometer based on a mixed Ce/Tb metal-organic framework

A mixed lanthanide metal-organic frameworks Ce1-xTbxFTPTC (x=0.042, 0.022) were synthesized by the simple solvothermal method and its temperature sensing was studied emphatically. The 2′-fluoro-[1,1′:4′,1′′-terphenyl]-3,3′′,5,5′′-tetracarboxylic acid (H4FTPTC) can efficiently sensitize Ce3+ and Tb3+ ions effectively, and it transfers the energy to Ce3+ and Tb3+ ions through resonance coupling. Accordingly, so Ce1-xTbxFTPTC (x=0.042, 0.022) can exhibit strong characteristic fluorescence of Ce3+ and Tb3+ ions. The Ce1-xTbxFTPTC (x=0.042, 0.022), as a proportional type luminescent thermometer shows excellent performance in the temperature range (313K-473K).

The comparison of the thermometric performance of optical ceramics, microcrystals and nanocrystals of Cr3+- doped Gd3Ga5O12 garnets

The remote temperature readout capability offered by luminescent thermometry has high application potential. Designing thermometers with predefined thermometric parameters is only possible by understanding the processes responsible for temperature-induced changes in the spectroscopic properties of phosphor. One of the key factors, that should be considered, is the influence of the morphology of the phosphor on their spectroscopic properties. In this work, we present for the first time an analysis of the influence of material morphology on the thermometric properties of a ratiometric luminescent thermometer based on the luminescence intensity ratio of 2E→4A2 to 4T2→4A2 emission bands in Gd3Ga5O12:Cr3+ nanocrystals, microcrystals and optical ceramics. As shown, limitations in the thermal coupling between the 2E and 4T2 levels occurring in the cryogenic temperature range allowed to achieve a relative sensitivity of 5.8%/K at 11 K in optical ceramics compared to 2.6%/K and 1.95%/K in microcrystals and nanocrystals, respectively.

Ratiometric Luminescent Thermometer Based on the Lanthanide Metal–Organic Frameworks by Thermal Curing

The high-performance optical thermometer probes are of great significance in diverse areas; lanthanide metal-organic frameworks (Ln-MOFs) are a promising candidate for luminescence temperature sensing owing to their unique luminescence properties. However, Ln-MOFs have poor maneuverability and stability in complex environments due to the crystallization properties, which then hinder their application scope. In this work, the Tb-MOFs@TGIC composite was successfully prepared using simple covalent crosslinking through uncoordinated -NH2 or COOH on Tb-MOFs reacting with the epoxy groups on TGIC {Tb-MOFs = [Tb2(atpt)3(phen)2(H2O)]n; H2atpt = 2-aminoterephthalic acid; phen = 1,10-phenanthroline monohydrate}. After curing, the fluorescence properties, quantum yield, lifetime, and thermal stability of Tb-MOFs@TGIC were remarkably enhanced. Meanwhile, the obtained Tb-MOFs@TGIC composites exhibit excellent temperature sensing properties in the low-temperature (Sr = 6.17% K-1 at 237 K), physiological temperature (Sr = 4.86% K-1 at 323 K), or high-temperature range (Sr = 3.88% K-1 at 393 K) with high sensitivity. In the temperature sensing process, the sensing mode of single emission changed into double emission for ratiometric thermometry owing to the back energy transfer (BenT) from Tb-MOFs to TGIC linkers, and the BenT process enhanced with the increase of temperature, which further improved the accuracy and sensitivity of temperature sensing. Most notably, the temperature-sensing Tb-MOFs@TGIC can be easily coated on the surface of polyimide (PI), glass plate, silicon pellet (SI), and poly(tetrafluoroethylene) plate (PTFE) substrates by a simple spraying method, which also exhibited an excellent sensing property, making it applicable for a wider T range measurement. This is the first example of a postsynthetic Ln-MOF hybrid thermometer operative over a wide temperature range including the physiological and high temperature based on back energy transfer.

A Multimodal Ratiometric Luminescent Thermometer Based on a Single-Dysprosium Metal–Organic Framework

The design of high-performance luminescent MOF thermometers with multi-operation modes has been long sought but remains a formidable challenge. In this work, for the first time, we present a multimodal luminescent ratiometric thermometer based on the single-lanthanide metal-organic framework (MOF) DyTPTC-2Me (H4TPTC-2Me = 2',5'-dimethyl-[1,1':4',1″-terphenyl]-3,3″,5,5″-tetracarboxylic acid). It not only has the characteristic luminescence of Dy3+ in which the atomic transitions from the 4I15/2 and 4F9/2 states (thermally coupled energy levels, TCELs) are included but also emits ligand fluorescence due to the efficient energy back-transfer of Dy3+ to the ligand, thus allowing accurate non-invasive determination of temperature by different modes. In particular, the TCEL-based emissions of the Dy3+ ions give ideal signals for measuring the temperature in the 303-423 K range. The emissions of the ligand and Dy3+ (4F9/2 → 6H13/2) are used for temperature sensing in the range of 423 to 503 K. Both two modes feature promising thermometric performance, including high relative sensitivity, high temperature resolution, and excellent repeatability. Their combination is thus beneficial to achieve more accurate temperature detection over a broad temperature range, which can broaden the application scope of the ratiometric luminescent thermometers.

Local Temperature Increments and Induced Cell Death in Intracellular Magnetic Hyperthermia.

The generation of temperature gradients on nanoparticles heated externally by a magnetic field is crucially important in magnetic hyperthermia therapy. But the intrinsic low heating power of magnetic nanoparticles, at the conditions allowed for human use, is a limitation that restricts the general implementation of the technique. A promising alternative is local intracellular hyperthermia, whereby cell death (by apoptosis, necroptosis, or other mechanisms) is attained by small amounts of heat generated at thermosensitive intracellular sites. However, the few experiments conducted on the temperature determination of magnetic nanoparticles have found temperature increments that are much higher than the theoretical predictions, thus supporting the local hyperthermia hypothesis. Reliable intracellular temperature measurements are needed to get an accurate picture and resolve the discrepancy. In this paper, we report the real-time variation of the local temperature on γ-Fe2O3 magnetic nanoheaters using a Sm3+/Eu3+ ratiometric luminescent thermometer located on its surface during exposure to an external alternating magnetic field. We measure maximum temperature increments of 8 °C on the surface of the nanoheaters without any appreciable temperature increase on the cell membrane. Even with magnetic fields whose frequency and intensity are still well within health safety limits, these local temperature increments are sufficient to produce a small but noticeable cell death, which is enhanced considerably as the magnetic field intensity is increased to the maximum level tolerated for human use, consequently demonstrating the feasibility of local hyperthermia.

Real‐Time In Situ Volatile Organic Compound Sensing by a Dual‐Emissive Polynuclear Ln‐MOF with Pronounced LnIII Luminescence Response

AbstractLanthanide metal–organic frameworks (Ln‐MOFs) are promising for luminescence detection of volatile organic compound (VOC) vapors, but usually suffer from the silent or quenched Ln3+ emission. Herein, we report a new dual‐emissive Eu‐MOF composed of the coordinatively unsaturated Eu9 clusters that afford abundant open metal sites to form a confined “binding pocket” to facilitate the preconcentration and recognition of VOCs. Single‐crystal structural analyses reveal that specific analytes can replace the OH oscillators in the first coordination sphere of Eu3+ and form a unique hydrogen‐bonding second‐sphere adduct tying adjacent Eu9 clusters together to minimize their nonradiative vibrational decay. With the promoted Eu3+ luminescence, the MOF realizes real‐time in situ visual sensing of THF vapor (<1 s) and shows a quantitative ratiometric response to the vapor pressure with a limit of detection down to 17.33 Pa. Also, it represents a top‐performing ratiometric luminescent thermometer.

Real-Time In Situ Volatile Organic Compound Sensing by a Dual-Emissive Polynuclear Ln-MOF with Pronounced LnIII Luminescence Response.

Lanthanide metal-organic frameworks (Ln-MOFs) are promising for luminescence detection of volatile organic compound (VOC) vapors, but usually suffer from the silent or quenched Ln3+ emission. Herein, we report a new dual-emissive Eu-MOF composed of the coordinatively unsaturated Eu9 clusters that afford abundant open metal sites to form a confined "binding pocket" to facilitate the preconcentration and recognition of VOCs. Single-crystal structural analyses reveal that specific analytes can replace the OH oscillators in the first coordination sphere of Eu3+ and form a unique hydrogen-bonding second-sphere adduct tying adjacent Eu9 clusters together to minimize their nonradiative vibrational decay. With the promoted Eu3+ luminescence, the MOF realizes real-time in situ visual sensing of THF vapor (<1 s) and shows a quantitative ratiometric response to the vapor pressure with a limit of detection down to 17.33 Pa. Also, it represents a top-performing ratiometric luminescent thermometer.