Size- and Emission-Controlled Synthesis of Full-Color Luminescent Metal-Organic Frameworks for Tryptophan Detection

The development of nanoscaled luminescent metal-organic frameworks (nano-LMOFs) with organic linker-based emission to explore their applications in sensing, bioimaging and photocatalysis is of great interest as material size and emission wavelength both have remarkable influence on their performances. However, there is lack of platforms that can systematically tune the emission and size of nano-LMOFs with customized linker design. Herein two series of fcu- and csq-type nano-LMOFs, with precise size control in a broad range and emission colors from blue to near-infrared, were prepared using 2,1,3-benzothiadiazole and its derivative based ditopic- and tetratopic carboxylic acids as the emission sources. The modification of tetratopic carboxylic acids using OH and NH2 as the substituent groups not only induces significant emission bathochromic shift of the resultant MOFs, but also endows interesting features for their potential applications. As one example, we show that the non-substituted and NH2 -substituted nano-LMOFs exhibit turn-off and turn-on responses for highly selective and sensitive detection of tryptophan over other nineteen natural amino acids. This work sheds light on the rational construction of nano-LMOFs with specific emission behaviours and sizes, which will undoubtedly facilitate their applications in related areas.

Building an emission library of donor–acceptor–donor type linker-based luminescent metal–organic frameworks

An emission library was built for donor–acceptor–donor type linker-based LMOFs, which can be used to rationally design organic linkers to prepare LMOFs with emission from deep blue to near-infrared.

Coordination Polymers Based on Highly Emissive Ligands: Synthesis and Functional Properties

Coordination polymers are constructed from metal ions and bridging ligands, linking them into solid-state structures extending in one (1D), two (2D) or three dimensions (3D). Two- and three-dimensional coordination polymers with potential voids are often referred to as metal-organic frameworks (MOFs) or porous coordination polymers. Luminescence is an important property of coordination polymers, often playing a key role in their applications. Photophysical properties of the coordination polymers can be associated with intraligand, metal-centered, guest-centered, metal-to-ligand and ligand-to-metal electron transitions. In recent years, a rapid growth of publications devoted to luminescent or fluorescent coordination polymers can be observed. In this review the use of fluorescent ligands, namely, 4,4'-stilbenedicarboxylic acid, 1,3,4-oxadiazole, thiazole, 2,1,3-benzothiadiazole, terpyridine and carbazole derivatives, naphthalene diimides, 4,4',4''-nitrilotribenzoic acid, ruthenium(II) and iridium(III) complexes, boron-dipyrromethene (BODIPY) derivatives, porphyrins, for the construction of coordination polymers are surveyed. Applications of such coordination polymers based on their photophysical properties will be discussed. The review covers the literature published before April 2020.

A dual-responsive luminescent sensor based on a water-stable Cd(ii)-MOF for the highly selective and sensitive detection of acetylacetone and Cr2O72− in aqueous solutions

Two water-stable cadmium(ii) MOFs were synthesized and characterized. 1 is the first dual-function Cd(ii)-MOF luminescent sensor for sensing acetylacetone and Cr₂O₇²⁻ in aqueous solution with high sensitivity and selectivity and good recyclability.

Fluorescent metal–organic frameworks based on mixed organic ligands: new candidates for highly sensitive detection of TNP

Novel metal–organic frameworks have been constructed based on fluorescent mixed ligands, which can be employed as efficient sensors.

Chemical Sensors Based on Metal-Organic Frameworks

Metal-organic frameworks (MOFs) as chemical sensors have developed rapidly in recent years. There have been many papers concerning this field and interest is still growing. The reason is that the specific merits of MOFs can be utilized to enhance sensitivity and selectivity by various energy/charge transfers occurring among different ligands, ligand, and metal centers, such as from ligands to metal centers or metal centers to ligands, as well as from MOF skeletons to guest species. This review intends to provide an update on recent progress in various applications of different MOF-based sensors on the basis of their luminescent and electrochemical responses towards small molecules, gas molecules, ions (cations and anions), pH, humidity, temperature, and biomolecules. MOF-based sensors function by utilizing different mechanisms, including luminescent responses of "turn-on" and "turn-off", as well as electrochemical responses.

Novel luminescent β-ketoimine derivative of 2,1,3-benzothiadiazole: synthesis, complexation with Zn(ii) and photophysical properties in comparison with related compounds

2,1,3-Benzothiadiazoles and their Zn complexes show fluorescence in different wavelength regions, one of the complexes reveals white emission.

Pillared metal organic frameworks for the luminescence sensing of small molecules and metal ions in aqueous solutions

Two pillared-layer MOFs as luminescent probes with multifunctional sensitivities to detect metal ions and small molecules were reported. Our results show that the luminescence intensities of 1a and 2a are highly sensitive to Fe³⁺ and Cd²⁺ ions and small molecules such as acetone and nitrobenzene.

Three 3D coordination polymers based on [1,1′:4′,1′′-terphenyl]-2′,4,4′′,5′-tetracarboxylate demonstrating magnetic properties and selective sensing of Al3+/Fe3+over mixed ions

Three 3D coordination polymers have been synthesized by using the 1,1′:4′,1′′-terphenyl]-2′,4,4′′,5′-tetracarboxylate acid and Cd(ii),Co(ii) and Mn(ii), the Cd(ii) complex shows selective sensing Al³⁺/Fe³⁺ over the mixed metal ions.

Assembly of Zn-metal organic frameworks based on a N-rich ligand: selective sorption for CO2 and luminescence sensing of nitro explosives

Two novel Zn(ii)-MOF have been successfully obtained. 1 exhibits a 3D framework with square channels and 2 shows a bi-pillared-layer type 3D framework. Furthermore, 1 exhibits selective CO₂/N₂ adsorption capacity and luminescence quenched toward acetone and nitrobenzene.

A dual-functional Cd(ii)–organic-framework demonstrating selective sensing of Zn2+ and Fe3+ ions exclusively and size-selective catalysis towards cyanosilylation

A dual-functional metal–organic-framework can selectively sense Zn²⁺ and Fe³⁺ ions over mixed metal ions and displays size-selective catalysis towards cyanosilylation of aldehydes.

Deprotonation-triggered Stokes shift fluorescence of an unexpected basic-stable metal-organic framework

A new three-dimensional porous metal-organic framework, JUC-119, constructed by a pyrene-based dendritic organic linker, H8TIAPy (H8TIAPy = 1,3,6,8-tetrakis(3,5-isophthalic acid)pyrene), and Eu(III) has been synthesized successfully. JUC-119 shows unexpected stability under a wide range of basic conditions from 0 to 0.01 M NaOH. Furthermore, with two carboxyl groups uncoordinated in each ligand, the crystals of JUC-119 show deprotonation-triggered Stokes shift fluorescence under basic conditions. As the concentration of base increases from 0 to 0.01 M NaOH, the luminescence emission of JUC-119 becomes gradually red shifted from 455 to 485 nm. In addition, the Stokes shift shows a good linear relationship to -log[OH(-)], which makes JUC-119 promising for base sensing.