Three Novel Isomeric Zinc Metal–Organic Frameworks from a Tetracarboxylate Linker

Highly fluorescent scandium-tetracarboxylate frameworks: selective detection of nitro-aromatic compounds, sensing mechanism, and their application

Recently, exploring new luminescent metal-organic frameworks (LMOFs) to selectively detect nitro-aromatic compounds (NACs) has been a hot topic of research. Simultaneously, it is still a challenging issue to understand the sensing mechanism of luminescent MOFs interacting with NACs at the molecular level. In this work, highly fluorescent Sc-tetracarboxylate frameworks (Sc-EBTC) have been successfully synthesized through a solvothermal method. The as-prepared Sc-EBTC crystals have good thermal stability, chemical stability as well as strong fluorescence (λ_ex = 320 nm and λ_em = 400 nm), and they can detect various NACs rapidly (as short as 30 s), selectively and efficiently by the "turn-off" fluorescence mechanism. The detection limits of Sc-EBTC toward 2,4-DNP and 4-NP are quantified to be 5.71 ppb and 6.26 ppb, respectively. Furthermore, to better understand the sensing mechanism, we attempt to use solid-state NMR and X-ray photoelectron spectroscopy to vividly characterize the charge transfer caused by the interaction between NAC molecules and the MOF at the molecular level. Additionally, test strips were made successfully for the practical detection of the NACs. This study demonstrates that the MOF constructed from the H₄EBTC ligands might be a promising candidate for the detection of trace NACs.

Two Isostructural URJC-4 Materials: From Hydrogen Physisorption to Heterogeneous Reductive Amination through Hydrogen Molecule Activation at Low Pressure

Herein, two novel isostructural metal-organic frameworks (MOFs) M-URJC-4 (M = Co, Ni; URJC = "Universidad Rey Juan Carlos") with open metal sites, permanent microposity, and large surface areas and pore volumes have been developed. These novel MOFs, with polyhedral morphology, crystallize in the monoclinic P2₁/c space group, exhibiting a three-dimensional structure with microporous channels along the c axis. Initially, they were fully characterized and tested in hydrogen (H₂) adsorption at different conditions of temperature and pressure. The physisorption capacities of both materials surpassed the gravimetric H₂ uptake shown by most MOF materials under the same conditions. On the basis of the outstanding adsorption properties, the Ni-URJC-4 material was used as a catalyst in a one-pot reductive amination reaction using various carbonyl compounds and primary amines. A possible chemical pathway to obtain secondary amines was proposed via imine formation, and remarkable performances were accomplished. This work evidences the dual ability of M-URJC-4 materials to be used as a H₂ adsorbent and a catalyst in reductive amination reactions, activating molecular H₂ at low pressures for the reduction of C═N double bonds and providing reference structural features for the design of new versatile heterogeneous materials for industrial application.

A pair of polymorphous metal–organic frameworks based on an angular diisophthalate linker: synthesis, characterization and gas adsorption properties

A pair of polymorphous MOFs derived from a bent diisophthalate ligand were synthesized by modulating solvothermal conditions, exhibiting comparable gas adsorption properties with respect to C₂H₂, CO₂ and CH₄.

MOF-Derived Flower-like MoS2@TiO2 Nanohybrids with Enhanced Activity for Hydrogen Evolution

A simple hydrothermal method is developed for synthesizing crystalline MoS₂@TiO₂ nanohybrids with metal-organic framework (MOF) as precursor. At an optimal ratio of 14.6 wt % MoS₂, the resultant material exhibits prominent catalytic activity for hydrogen evolution reaction (HER) with a high hydrogen production rate of 10 046 μmol h^-1 g^-1 under visible light illumination with fluorescein as photosensitizer. Furthermore, the synthesized catalyst also possesses an attractive electrocatalytic activity with an onset overpotential of -300 mV (vs RHE) and a Tafel slope of ∼81 mV dec^-1. The enhanced catalyst performances are mainly attributed to the in situ formed active sites, featuring a uniform dispersion and strong connection of MoS₂ and TiO₂, which can facilitate electron transfer. In addition, the MoS₂@TiO₂ nanohybrids are highly stable and completely recyclable over HER.

3,5-Bis((4′-carboxylbenzyl)oxy)benzoilate-based coordination polymers: their synthesis, structural characterization, and sensing properties

The structural characterization of four 3,5-bis((4′-carboxylbenzyl)oxy)benzoilate-based coordination polymers has been reported, and the sensing ability of 2 and 4 on NB has been investigated.

Mixed ligand two dimensional Cd(ii)/Ni(ii) metal organic frameworks containing dicarboxylate and tripodal N-donor ligands: Cd(ii) MOF is an efficient luminescent sensor for detection of picric acid in aqueous media

Two water stable MOFs [M(BrIP)(TIB)]_n [M = Cd(ii), Ni(ii)] have been prepared. Cd(ii) MOF serves as photoluminescent sensor for detection of TNP in aqueous phase.

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.

Template-directed construction of conformational supramolecular isomers for bilayer porous metal–organic frameworks with distinct gas sorption behaviors

Two conformationally isomeric Co(ii)-based bilayer porous coordination frameworks can be prepared using different solvent templates, which show distinct gas sorption behaviors.

Synthesis of a series of coordination polymers based on mixed ligands to tune the structural dimension

Schematic illustrating the 2D network of complex 1. Color code: yellow, Mn; cob²⁻ ligand, red.