A Eu/Tb mixed lanthanide coordination polymer with rare 2D thick layers: Synthesis, characterization and ratiometric temperature sensing

Transformational Modulation of Fluorescence to Room Temperature Phosphorescence in Metal-Organic Frameworks with Flexible C-S-C Bonds

Photoluminescent metal-organic frameworks (MOFs) have been a subject of considerable interest for many years. However, the regulation of excited states of MOFs at the single crystal level remains restricted due to a lack of control methods. The singlet-triplet emissive property can be significantly influenced by crystal conformational distortions. This review introduces an intelligent responsive MOF material, denoted as LIFM-SHL-3a, characterized by flexible C-S-C bonds. LIFM-SHL-3a integrates elastic structural dynamics with fluorescence and room temperature phosphorescence (RTP) modulation under heating conditions. The deformable carbon-sulfur bond essentially propels the distortion of molecular conformation and alters the stacking mode, as illustrated by single-crystal-to-single-crystal transformation detection. The deformation of flexible C-S-C bonds leads to different noncovalent interactions in the crystal system, thereby achieving modulation of the fluorescence (F) and RTP bands. In the final state structure, the ratio of fluorescence is 66.7%, and the ratio of RTP is 32.6%. This stands as a successful demonstration of modulating F/RTP within the dynamic MOF, unlocking potential applications in optical sensing and beyond. Especially, a PL thermometer with a relative sensitivity of 0.096-0.104%·K-1 in the range of 300-380 K and a H2S probe with a remarkably low LOD of 125.80 nM can be obtained using this responsive MOF material of LIFM-SHL-3a.

Achieving gas pressure-dependent luminescence from an AIEgen-based metal-organic framework

Materials exhibiting aggregation-induced emission (AIE) behaviour enable strong emission in solid state and can respond to various external stimuli, which may facilitate the development of materials for optical sensing, bioimaging or optoelectronic devices. Herein, we use an AIE luminogen 2’,5’-diphenyl-[1,1’:4’,1”-terphenyl]-4,4”-dicarboxylic acid as the ligand to prepare an AIEgen-based MOF (metal-organic framework) named FJI-H31. FJI-H31 exhibits bright luminescence under ambient conditions (under air and at room temperature), but almost no emission is observed under vacuum. Our investigation shows that the emission intensity displays a smooth and reversible enhancement with increased gas pressure, which may be attributed to the restriction of intramolecular motion brought by structural deformation under pressure stimulus. Unlike most pressure-responsive MOFs, the luminescence reverts to its original state once gas pressure recovers. By virtue of its unique optical properties, a luminescent MOF with sensing ability of gas-pressure is realized.

Compounds displaying aggregation-induced emission behavior may have application in the preparation of smart materials. Here, the authors report a luminogen-containing metal-organic framework for which luminescence intensity changes are observed in response to gas pressure.

Metallopolymers for advanced sustainable applications

Since the development of metallopolymers, there has been tremendous interest in the applications of this type of materials. The interest in these materials stems from their potential use in industry as catalysts, biomedical agents in healthcare, energy storage and production as well as climate change mitigation. The past two decades have clearly shown exponential growth in the development of many new classes of metallopolymers that address these issues. Today, metallopolymers are considered to be at the forefront for discovering new and sustainable heterogeneous catalysts, therapeutics for drug-resistant diseases, energy storage and photovoltaics, molecular barometers and thermometers, as well as carbon dioxide sequesters. The focus of this review is to highlight the advances in design of metallopolymers with specific sustainable applications.