Advances in ionic liquids as fluorescent sensors

Ionic liquids (ILs) are a class of liquid salts with characteristics such as a low melting point, an ionic nature, non-volatility, and tunable properties. Because of their adaptability, they have a significant influence in the field of fluorescence. This paper reviews the primary literature on the use of ILs in fluorescence sensing technologies. The kind of target material is utilized to classify the fluorescence sensors made with the use of ILs. They include using ILs as probes for metals, nitro explosives, small organic compounds, anions, and gases. The efficacy of an IL-based fluorescence sensor depends on the precise design to guarantee specificity, sensitivity, and a consistent reaction to the desired analyte. The precise method can differ depending on the chemical properties of the IL, the choice of fluorophore, and the interactions with the analyte. Overall, the viability of the aforementioned materials for chemical analysis is evaluated, and prospective possibilities for further development are identified.

Chiral Metal-Organic Frameworks

In the past two decades, metal-organic frameworks (MOFs) or porous coordination polymers (PCPs) assembled from metal ions or clusters and organic linkers via metal-ligand coordination bonds have captivated significant scientific interest on account of their high crystallinity, exceptional porosity, and tunable pore size, high modularity, and diverse functionality. The opportunity to achieve functional porous materials by design with promising properties, unattainable for solid-state materials in general, distinguishes MOFs from other classes of materials, in particular, traditional porous materials such as activated carbon, silica, and zeolites, thereby leading to complementary properties. Scientists have conducted intense research in the production of chiral MOF (CMOF) materials for specific applications including but not limited to chiral recognition, separation, and catalysis since the discovery of the first functional CMOF (i.e., d- or l-POST-1). At present, CMOFs have become interdisciplinary between chirality chemistry, coordination chemistry, and material chemistry, which involve in many subjects including chemistry, physics, optics, medicine, pharmacology, biology, crystal engineering, environmental science, etc. In this review, we will systematically summarize the recent progress of CMOFs regarding design strategies, synthetic approaches, and cutting-edge applications. In particular, we will highlight the successful implementation of CMOFs in asymmetric catalysis, enantioselective separation, enantioselective recognition, and sensing. We envision that this review will provide readers a good understanding of CMOF chemistry and, more importantly, facilitate research endeavors for the rational design of multifunctional CMOFs and their industrial implementation.

Enantioselective Gel Phase Synthesis of Metal-Organic Materials

We report the asymmetric synthesis of homochiral metal-organic materials (MOMs) in chiral gels from achiral components. The enantioselectivity of MOMs depends on the chirality of the gel, whereas the synthesis performed in solution phase and achiral gels resulted in conglomerates.

Homochiral metal-organic frameworks for enantioseparation

Obtaining homochiral compounds is of high importance to human health and environmental sustainability. Currently, enantioseparation is one of the most effective approaches to obtain homochiral compounds. Thanks to their controlled synthesis and high efficiency, homochiral metal-organic frameworks (HMOFs) are one of the most widely studied porous materials to enable enantioseparation. In this review, we discuss the chiral pocket model in depth as the key to unlock enantioselective separation mechanisms in HMOFs. In particular, we classify our discussion of these chiral pockets (also regarded as "molecular traps") into: (a) achiral/chiral linker based helical channels as a result of packing modality; and (b) chiral pores inherited from chiral ligands. Driven by a number of mechanisms of enantioseparation, conceptual advances have been recently made in the design of HMOFs for achieving high enantioseparation performances. Herein, these are systematically categorised and discussed. Further we elucidate various applications of HMOFs as regards enantioseparation, systematically classifying them into their use for purification and related analytical utility according to the reported examples. Last but not the least, we discuss the challenges and perspectives concerning the rational design of HMOFs and their corresponding enantioseparations.

Synthesis of Chiral MOF-74 Frameworks by Post-Synthetic Modification by Using an Amino Acid

The synthesis of chiral metal-organic frameworks (MOFs) is highly relevant for asymmetric heterogenous catalysis, yet very challenging. Chiral MOFs with MOF-74 topology were synthesised by using post-synthetic modification with proline. Vibrational circular dichroism studies demonstrate that proline is the source of chirality. The solvents used in the synthesis play a key role in tuning the loading of proline and its interaction with the MOF-74 framework. In N,N'-dimethylformamide, proline coordinates monodentate to the Zn2+ ions within the MOF-74 framework, whereas it is only weakly bound to the framework when using methanol as solvent. Introducing chirality within the MOF-74 framework also leads to the formation of defects, with both the organic linker and metal ions missing from the framework. The formation of defects combined with the coordination of DMF and proline within the framework leads to a pore blocking effect. This is confirmed by adsorption studies and testing of the chiral MOFs in the asymmetric aldol reaction between acetone and para-nitrobenzaldehyde.

Chiral covalent organic frameworks: design, synthesis and property

Owing to the unique structural features and facile tunability of the subcomponents and channels, chiral COFs show great potential in heterogeneous catalysis, enantioselective separation, and recognition.

Aqueous-phase detection of antibiotics and nitroaromatic explosives by an alkali-resistant Zn-MOF directed by an ionic liquid

An alkali-resistant 3D anionic Zn-MOF directed by [BMI]Br ionic liquid has been synthesized for aqueous-phase detection of antibiotics and nitroaromatic explosives.

Homochiral coordination polymers constructed from V-shaped oxybisbenzoyl-based amino acid derivatives: structures, magnetic and photoluminescence properties

Five novel amino acid-modified HCPs have been prepared using the V-shaped semi-rigid 4,4′-oxybis(benzoic acid) instead of usual rigid polycarboxylate units.

Synthesis and characterization of two layered aluminophosphates [R-C8H12N]8[H2O]2·[Al8P12O48H4] and [S-C8H12N]8[H2O]2·[Al8P12O48H4] with a mirror symmetric feature and their proton conductivity

Two homochiral aluminophosphates with a mirror symmetric feature were synthesized. H-bond chains play a key role in chirality and proton conductivity.

Achiral aromatic solvent-induced assembly of 3-D homochiral porous 3d–4f heterometallic-organic frameworks based on isonicotinic acid

Via induction of achiral aromatic solvents, two 3-D monochiral 3d–4f MOFs (1 and 2) from the ligand HIN without any chiral auxiliary are uncommonly constructed. And the results show homochirality of 1 and 2 are enantiopurity rather than enantiomeric excess.

pH-Stable Eu- and Tb-organic-frameworks mediated by an ionic liquid for the aqueous-phase detection of 2,4,6-trinitrophenol (TNP)

pH-Stable Eu- and Tb-organic-frameworks mediated by ionic liquids for the aqueous-phase detection of 2,4,6-trinitrophenol (TNP).

Structures of Metal-Organic Frameworks with Rod Secondary Building Units

Rod MOFs are metal-organic frameworks in which the metal-containing secondary building units consist of infinite rods of linked metal-centered polyhedra. For such materials, we identify the points of extension, often atoms, which define the interface between the organic and inorganic components of the structure. The pattern of points of extension defines a shape such as a helix, ladder, helical ribbon, or cylinder tiling. The linkage of these shapes into a three-dimensional framework in turn defines a net characteristic of the original structure. Some scores of rod MOF structures are illustrated and deconstructed into their underlying nets in this way. Crystallographic data for all nets in their maximum symmetry embeddings are provided.

Chiral chemistry of metal-camphorate frameworks

This critical review presents the various synthetic approaches and chiral chemistry of metal-camphorate frameworks (MCamFs), which are homochiral metal-organic frameworks (MOFs) constructed from a camphorate ligand. The interest in this unique subset of homochiral MOFs is derived from the many interesting chiral features for both materials and life sciences, such as asymmetrical synthesis or crystallization, homochiral structural design, chiral induction, absolute helical control and ligand handedness. Additionally, we discuss the potential applications of homochiral MCamFs. This review will be of interest to researchers attempting to design other homochiral MOFs and those engaged in the extension of MOFs for applications such as chiral recognition, enantiomer separation, asymmetric catalysis, nonlinear sensors and devices.

Centric and acentric networks using low-symmetry heterotopic carboxylate/pyridyl ligands

Four isomeric pyridyl/carboxylate ligands demonstrate the appliability of low-symmetry ligands to the formation of chiral materials.

Three different metal-organic frameworks derived from a one-pot crystallization and their controllable synthesis

Three different Co-MOFs, [Co3(L)2(DPDP)]n (1), [Co(HL)(DPDP)]n (2) and {[Co(HL)(1/2DPDP)3(H2O)]·H2O}n (3) (H3L = 4,4',4''-(nitrilotris(methylene))tribenzoic acid, DPDP = 4,4'-(2,5-dibutoxy-1,4-phenylene)dipyridine) have been co-crystallized in a one-pot reaction. Based on the significant differences between the three structures, we adopt solvents to ultimately regulate acquisition of pure crystals of the three compounds.

Spontaneous symmetry breaking of Co(ii) metal–organic frameworks from achiral precursors via asymmetrical crystallization

Enantioenriched 3D pseudo-enantiomorphs integrating porosity, chirality and magnetism together with different colour and morphology were obtained through spontaneous symmetry breaking.

Chiral or achiral: four isomeric Cd(ii) coordination polymers based on phenylenediacrylate ligands

The isomeric coordination polymers derived fromp- andm-phenylenediacrylates contain similar homochiral motifs (hydrogen-bonded layers or μ-O_carboxylatebridged helical chains), but only themligand, with assistance of hydrogen bonds, induces spontaneous resolution to generate 3D homochiral networks.

Influence of ionic liquids on the syntheses and structures of Mn(ii) coordination polymers based on multidentate N-heterocyclic aromatic ligands and bridging carboxylate ligands

[RMI]Br probably serves as a template directing agent for the formation of a cluster helicate in 2, while it serves as a mineralizing agent in 3–6. Additionally, [RMI]Br could obviously improve the crystal yield of 7.

Asymmetric induction in homochiral MOFs: from interweaving double helices to single helices

A pair of homochiral metal–organic frameworks with interweaving double helices from enantiopure ligands and single helices braided by 4,4′-bipyridine and cadmium clusters have been synthesized successfully as a result of asymmetric induction.

Ionic liquid directed syntheses of water-stable Eu– and Tb–organic-frameworks for aqueous-phase detection of nitroaromatic explosives

Ionic liquid directed syntheses of water-stable Eu– and Tb–organic-frameworks for aqueous-phase detection of nitroaromatic explosives.

Chiral template induced homochiral MOFs built from achiral components: SHG enhancement and enantioselective sensing of chiral alkamines by ion-exchange

A homochiral anionic framework built from achiral components was synthesized for enantioselective sensing of chiral alkamines. Ion-exchange with polar or chiral organic cations leads to the enhancement of the SHG efficiency.

Surfactant-thermal method to synthesize a novel two-dimensional oxochalcogenide

A new two-dimensional (2D) oxosulfide, (N2H4)2Mn3Sb4S8(μ3-OH)2 (1), has been successfully synthesized under surfactant-thermal conditions with hexadecyltributylphosphonium bromide as the surfactant. Compound 1 has a layered structure and contains a novel [Mn3(μ3-OH)2]n chain along the b-axis. The photocatalytic activity for compound 1 has been demonstrated under visible-light irradiation and continuous H2 evolution was observed. Our results indicate that surfactant-thermal synthesis could be a promising method for growing novel crystalline oxochalcogenides with interesting structures and properties.