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.

Amino-Functionalized Single-Lanthanide Metal-Organic Framework as a Ratiometric Fluorescent Sensor for Quantitative Visual Detection of Fluoride Ions.

Excessive content of fluoride ions (F-) in water will lead to water pollution and endanger human health, so the research on the method of low-cost, rapid, and efficient detection of F- is of particular significance. In this work, an amino-functionalized ligand with an appropriate triplet energy excited state, 2'-amino-[1,1':4',1″-terphenyl]-3,3″,5,5″-tetracarboxylic acid (H4TPTC-NH2), was selected to construct a luminescent single-lanthanide metal-organic framework, EuTPTC-NH2, with uncoordinated amino groups for the detection of F-. Based on host-guest interactions, that is, hydrogen bonds formed between the free amino groups and F- ions, EuTPTC-NH2 was developed as a ratiometric fluorescence probe for F- detection with good anti-interference ability, low detection limit, high water stability, and selectivity. It was found that EuTPTC-NH2 has an excellent linear response to F- in the concentration range of 0-80 µM with high sensitivity and a low detection limit of 11.26 µM. A hydrogel membrane based on the combination of EuTPTC-NH2 and agarose was also prepared for the quantitative visual detection of F- in water.

Water-Stable Eu6-Cluster-Based fcu-MOF with Exposed Vinyl Groups for Ratiometric and Fluorescent Visual Sensing of Hydrogen Sulfide.

Detection of H2S in the biological system has attracted enormous attention in recent years. In this work, a new vinyl-functionalized metal-organic framework (MOF), [(Me2NH2)2] [Eu6(µ3-OH)8(BDC-CH═CH2)6(H2O)6] (Eu-BDC-CH═CH2, BDC-CH═CH2 = 2-vinylterephthalic acid), was synthesized under solvothermal conditions. The vinyl groups in the ligands can not only modulate the "antenna effect" of the ligand on Eu3+ ions but also serve as an exposed reactive site to allow for the quantitative detection of H2S by Eu-BDC-CH═CH2. The ratiometric fluorescent probe has the advantages of water stability, acid-base stability (pH = 2-11), fast response (<2 min), high selectivity, and sensitivity (LOD = 38.4 µM). We also used Eu-BDC-CH═CH2 to detect and analyze H2S in tap and lake waters, demonstrating the potential of the probe for biological and environmental applications. In addition, the MOF-based agarose hydrogel film allows for the visual detection of H2S via a smartphone by identifying the RGB values. The vinyl-functionalized MOF can thus be a powerful sensing platform for H2S.

Recent progress on porous MOFs for process-efficient hydrocarbon separation, luminescent sensing, and information encryption.

Metal-organic frameworks (MOFs), as an emerging class of porous materials, excel in designability, regulatability, and modifiability in terms of their composition, topology, pore size, and surface chemistry, thus affording a huge potential for addressing environment and energy-related challenges. In particular, MOFs can be applied as porous adsorbents for the purification of industrially important hydrocarbons through certain process-efficient separation schemes based on selectivity-reversed adsorption and multicomponent separation. Moreover, the vast combination possibilities and controllable and engineerable luminescent units of MOFs make them a versatile platform to develop functionally tailored materials for luminescent sensing and optical data encryption. In this feature article, we summarize the recent progress in the use of porous MOFs for the separation and purification of acetylene (C2H2) and ethylene (C2H4) based on selectivity-reversed adsorption and multicomponent separation strategies. Moreover, we highlight the advances over the past three years in the field of MOF-based luminescent materials for thermometry, turn-on sensing, and information encryption.