Synthesis,Structure, and Magnetic Properties of a Copper(II) Metal‐Organic Framework with Biphenyl‐2,2′,4,4′‐tetracarboxylic Acid

The 2D Cu^II metal‐organic framework [Cu₂(bptc)(H₂O)₄]_n · 4nH₂O ( 1 ) (H₄bptc = biphenyl‐2,2′,4,4′‐tetracarboxylic acid) was hydrothermally synthesized and characterized by single‐crystal X‐ray diffraction and magnetic measurements. In the structure, bptc^4– serves as a twisted Π‐shaped organic building block to connect paddlewheel [Cu₂(COO)₄] dinuclear units and mononuclear units through 2‐/2′‐carboxylate and 4‐/4′‐carboxylate, respectively. According to the magnetic analysis using a dimer‐plus‐monomer model, strong antiferromagnetic coupling is operative within the dinuclear unit (J = –311 cm^–1 based on H = –J S ₁ S ₂), and the compound behaves like a mononuclear molecule at low temperature.     

A Microporous Anionic Metal–Organic Framework for Sensing Luminescence of Lanthanide(III) Ions and Selective Absorption of Dyes by Ionic Exchange

Herein, a novel anionic framework with primitive centered cubic (pcu) topology, [(CH₃)₂NH₂]₄[(Zn₄dttz₆)Zn₃]?15 DMF?4.5 H₂O, ( IFMC‐2 ; H₃dttz=4,5‐di(1H‐tetrazol‐5‐yl)‐2H‐1,2,3‐triazole) was solvothermally isolated. A new example of a tetranuclear zinc cluster {Zn₄dttz₆} served as a secondary building unit in IFMC‐2 . Furthermore, the metal cluster was connected by Zn^II ions to give rise to a 3D open microporous structure. The lanthanide(III)‐loaded metal–organic framework (MOF) materials Ln³⁺@IFMC‐2 , were successfully prepared by using ion‐exchange experiments owing to the anionic framework of IFMC‐2 . Moreover, the emission spectra of the as‐prepared Ln³⁺@IFMC‐2 were investigated, and the results suggested that IFMC‐2 could be utilized as a potential luminescent probe toward different Ln³⁺ ions. Additionally, the absorption ability of IFMC‐2 toward ionic dyes was also performed. Cationic dyes can be absorbed, but not neutral and anionic dyes, thus indicating that IFMC‐2 exhibits selective absorption toward cationic dyes. Furthermore, the cationic dyes can be gradually released in the presence of NaCl.     

Synthesis,Structure, and Characterization of a Microporous Metal‐Organic Framework with PtS Topology

The microporous metal‐organic framework Cd₂(ABTC)(H₂O)(DMA)₂ · H₂O · 3DMA ( 1 ) (H₄ABTC = 3, 3′,5, 5′‐azobenzenetetracarboxylic acid; DMA = N,N′‐dimethylacetamide) was prepared by solvothermal reaction and characterized. X‐ray structure analysis revealed that compound 1 is a three‐dimensional (3D) open framework with 2D channels. The topology is based on a PtS net, constructed of 4‐connected rectangular ABTC^4– units with 4‐connected tetrahedral dinuclear Cd₂(CO₂)₄(H₂O)(DMA)₂ secondary building units (SBUs). The solid‐state excitation‐emission spectra showed that the strongest emission peak is at 403 nm upon excitation at λ = 287 nm.     

Antiperovskite Intermetallic Nanoparticles for Enhanced Oxygen Reduction

Antiperovskite Co₃InC_0.7N_0.3 nanomaterials with highly enhanced oxygen reduction reaction (ORR) performance were prepared by tuning nitrogen contents through a metal–organic framework (MOF)‐derived strategy. The nanomaterial surpasses all reported noble‐metal‐free antiperovskites and even most perovskites in terms of onset potential (0.957 V at J=0.1 mA cm^?2) and half‐wave potential (0.854 V). The OER and zinc–air battery performance demonstrate its multifunctional oxygen catalytic activities. DFT calculation was performed and for the first time, a 4 e^? dissociative ORR pathway on (200) facets of antiperovskite was revealed. Free energy studies showed that nitrogen substitution could strengthen the OH desorption as well as hydrogenation that accounts for the enhanced ORR performance. This work expands the scope for material design via tailoring the nitrogen contents for optimal reaction free energy and hence performance of the antiperovskite system.     

Magnetic Coupling between Metal Spins through the 7,7,8,8‐Tetracyanoquinodimethane (TCNQ) Dianion

A family of magnetic metal–organic frameworks, (Ph₃PMe)₂[M₂(TCNQ)₃] {M=Fe²⁺, Co²⁺, Ni²⁺ and Zn²⁺} have been prepared and structurally characterized. The honeycomb‐like “layers” consist of M^II ions doubly bridged with dinitrilomethane moieties of two 7,7,8,8‐tetracyanoquinodimethane (TCNQ) dianions which are further connected through phenyl rings to form a 3D dianionic framework [M₂TCNQ₃]^2? with Ph₃PMe⁺ cations filling cavities that run along the c axis. Studies of the magnetic coupling through the TCNQ dianion in these structures revealed that it can promote long‐range magnetic ordering despite the long coupling pathway.     

Poly[μ3‐hydroxido‐μ6‐sulfato‐μ3‐(1,2,4‐triazolato‐κ3N1:N2:N4)‐dicadmium(II)]: a cadmium–triazolate coordination polymer with a pseudo‐cubane‐like tetranuclear cluster

The title complex, [Cd₂(C₂H₂N₃)(OH)(SO₄)]_n, is a three‐dimensional metal–organic framework consisting of pseudo‐cubane‐like tetranuclear cadmium clusters, which are formed by four Cd^II atoms, two sulfate groups and two hydroxide groups. The tetranuclear cadmium clusters are connected into a layered substructure by Cd—O bonds and adjacent layers are linked by triazolate ligands into a three‐dimensional network. A photoluminescent study revealed that the complex exhibits a strong emission in the visible region which probably originates from a π–π* transition.     

Conversion from Heterometallic to Homometallic Metal–Organic Frameworks

Two new heterometallic metal–organic frameworks (MOFs), LnZnTPO 1 and 2 , and two homometallic MOFs, LnTPO 3 and 4 (Ln=Eu for 1 and 3 , and Tb for 2 and 4 ; H₃TPO=tris(4-carboxyphenyl)phosphine oxide) were synthesized, and their structures and properties were analyzed. They were prepared by solvothermal reaction of the C₃-symmetric ligand H₃TPO with the corresponding metal ion(s) (a mixture of Ln³⁺ and Zn²⁺ for 1 and 2 , and Ln³⁺ alone for 3 and 4 ). Single-crystal XRD (SXRD) analysis revealed that 1 and 3 are isostructural to 2 and 4 , respectively. TGA showed that the framework is thermally stable up to about 400 °C for 1 and 2 , and about 450 °C for 3 and 4 . PXRD analysis showed their pore-structure distortions without noticeable framework–structure changes during drying processes. The shapes of gas sorption isotherms for 1 and 3 are almost identical to those for 2 and 4 , respectively. Solvothermal immersion of 1 and 2 in Tb³⁺ and Eu³⁺ solutions resulted in the framework metal-ion exchange affording 4 and 3 , respectively, as confirmed by photoluminescence (PL), PXRD, IR, inductively coupled plasma atomic emission spectroscopy (ICP-AES), and energy-dispersive X-ray (EDX) analyses.     

Self‐Assembly versus Stepwise Synthesis: Heterometal–Organic Frameworks Based on Metalloligands with Tunable Luminescence Properties

A new family of heterometal–organic frameworks has been prepared by two synthesis strategies, in which IFMC‐26 and IFMC‐27 are constructed by self‐assembly and IFMC‐28 is obtained by stepwise synthesis based on the metalloligand (IFMC=Institute of Functional Material Chemistry). IFMC‐26 is a (3,6)‐connected net and IFMC‐27 is a (4,8)‐connected 3D framework. The metalloligands {Ni(H₄L)}(NO₃)₂ are connected by binuclear lanthanide clusters giving rise to a 2D sheet structure in IFMC‐28 . Notably, IFMC‐26‐Eu _x Tb _y and IFMC‐28‐Eu _x Tb _y have been obtained by changing the molar ratios of raw materials. Owing to the porosity of IFMC‐26 , Tb³⁺@IFMC‐26‐Eu and Eu³⁺@IFMC‐26‐Tb are obtained by postencapsulating Tb^III and Eu^III ions into the pores, respectively. Tunable luminescence in metal–organic frameworks is achieved by the two kinds of doping methods. In particular, the quantum yields of heterometal–organic frameworks are apparently enhanced by postencapsulation of Ln^III ions.     

Crystal structure and pale‐yellow emitting properties of K3Gd1–xDyxB6O12 solid solutions

A new potassium dysprosium polyborate, K₃DyB₆O₁₂, has been prepared via the high‐temperature molten salt method and structurally characterized by single‐crystal X‐ray diffraction analysis. The structure can be described as a three‐dimensional framework composed of isolated bicyclic [B₅O₁₀]^5? groups and Dy³⁺ and K⁺ ions. The Fourier transform IR (FT–IR) and ultraviolet–visible (UV–Vis) spectra were investigated. A series of K₃Gd_1–xDy_xB₆O₁₂ phosphors was prepared and their photoluminescence properties were studied. The K₃Gd_1–xDy_xB₆O₁₂ phosphors exhibit a strong yellow emission band at 577 nm (the ⁴F_9/2→⁶H_13/2 transition of Dy³⁺) under UV excitation of 275 nm (the ⁸S_7/2→⁶I_J transition of Gd³⁺), suggesting the occurrence of the energy transfer Gd³⁺→Dy³⁺. The optimized doping concentration of the Dy³⁺ ion was 8 mol%. We may expect that K₃Gd_1–xDy_xB₆O₁₂ is a promising pale‐yellow emission phosphor for visual displays or solid‐state lighting.     

A Stable Polyoxometalate‐Pillared Metal–Organic Framework for Proton‐Conducting and Colorimetric Biosensing

A stable metal–organic framework pillared by Keggin‐type polyoxometalate, Cu₆(Trz)₁₀(H₂O)₄[H₂SiW₁₂O₄₀]?8 H₂O (Trz=1,2,4‐triazole) ( 1 ), has been prepared under hydrothermal condition. The 2D layer structure with a 22‐member ring was formed by Cu²⁺ ions, which are connected with each other via the Trz ligands on the ab plane. Thus, the 2D layers are further interconnected through Keggin polyoxoanions to generate a 3D porous network with a small 1D channel. Moreover, the presence of polyoxoanions make it exhibit selective adsorption of water and proton‐conducting properties. Additionally it showed efficient intrinsic peroxidase‐like activity, providing a simple and sensitive colorimetric assay to detect H₂O₂.     

Highly Selective Detection of 2,4,6‐Trinitrophenol and Cu2+ Ions Based on a Fluorescent Cadmium–Pamoate Metal–Organic Framework

A luminescent cadmium–pamoate metal–organic framework, [Cd₂(PAM)₂(dpe)₂(H₂O)₂]?0.5(dpe) ( 1 ), has been synthesized under hydrothermal conditions by using π‐electron‐rich ligands 4,4′‐methylenebis(3‐hydroxy‐2‐naphthalenecarboxylic acid) (H₂PAM) and 1,2‐di(4‐pyridyl)ethylene (dpe). Its structure is composed of both mononuclear and dinuclear Cd^II building units, which are linked by the PAM and dpe ligands, resulting in a (4,8)‐connected 3D framework. The π‐conjugated dpe guests are located in a 1D channel of 1 . The strong emission of 1 could be quenched efficiently by trace amounts of 2,4,6‐trinitrophenol (TNP), even in the presence of other competing analogues such as 4‐nitrophenol, 2,6‐dinitrotoluene, 2,4‐dinitrotoluene, nitrobenzene, 1,3‐dinitrobenzene, hydroquinone, dimethylbenzene, and bromobenzene. The high sensitivity and selectivity of the fluorescence response of 1 to TNP shows that this framework could be used as an excellent sensor for identifying and quantifying TNP. In the same manner, 1 also exhibits superior selectivity and sensitivity towards Cu²⁺ compared with other metal ions such as Zn²⁺, Mn²⁺, Mg²⁺, K⁺, Na⁺, Ni²⁺, Co²⁺, and Ca²⁺. This is the first MOF that can serve as a dual functional fluorescent sensor for selectively detecting trace amounts of TNP and Cu²⁺.     

Microwave‐Assisted Modular Fabrication of Nanoscale Luminescent Metal‐Organic Framework for Molecular Sensing

Miniaturizing the size of metal‐organic framework (MOF) crystals to the nanometer scale is challenging, but it provides more advanced applications without changing the characteristic features itself. It is especially useful to investigate the correlation between the porous properties and the interfacial structures of nanocrystals. Using amino acids as capping agents, nanoscale Tb‐MOF‐76 is fabricated rapidly by means of microwave‐assisted methods. Both the modular effects of the amimo acids and the acid–base environment of the reaction medium have an important impact on the morphologies and dimensions of Tb‐MOF‐76. The structures of the samples are confirmed by powder X‐ray diffraction, and the morphologies are characterized by SEM. Photoluminescence studies reveal that these Tb‐MOF‐76 materials exhibit a green emission corresponding to the transition ⁵D₄→⁷F_J of Tb³⁺ ions under UV‐light excitation, which is sensitive to small organic molecules in solution.     

An Americium‐Containing Metal–Organic Framework: A Platform for Studying Transplutonium Elements

The synthesis, structure, and spectroscopic characterization of the first transplutonium metal–organic framework (MOF) is described. The preparation and structure of Am‐GWMOF‐6, [Am₂(C₆H₈O₄)₃(H₂O)₂][(C₁₀H₈N₂)], is analogous to that of the isostructural trivalent lanthanide‐only containing material GWMOF‐6. The presented MOF architecture is used as a platform to probe Am³⁺ coordination chemistry and guest‐enhanced luminescent emission, whereas the framework itself provides a means to monitor the effects of self‐irradiation upon crystallinity over time. Presented here is a discussion of these properties and the opportunities that MOFs provide in the structural and spectroscopic study of actinides.     

Selective Sensing of Fe3+ and Al3+ Ions and Detection of 2,4,6‐Trinitrophenol by a Water‐Stable Terbium‐Based Metal–Organic Framework

A water‐stable luminescent terbium‐based metal–organic framework (MOF), {[Tb(L₁)_1.5(H₂O)] ? 3 H₂O}_n (Tb‐MOF), with rod‐shaped secondary building units (SBUs) and honeycomb‐type tubular channels has been synthesized and structurally characterized by single‐crystal X‐ray diffraction. The high green emission intensity and the microporous nature of the Tb‐MOF indicate that it can potentially be used as a luminescent sensor. In this work, we show that Tb‐MOF can selectively sense Fe³⁺ and Al³⁺ ions from mixed metal ions in water through different detection mechanisms. In addition, it also exhibits high sensitivity for 2,4,6‐trinitrophenol (TNP) in the presence of other nitro aromatic compounds in aqueous solution by luminescence quenching experiments.     

Magnetic Properties of a Single‐Molecule Lanthanide–Transition‐Metal Compound Containing 52 Gadolinium and 56 Nickel Atoms

Monodisperse metal clusters provide a unique platform for investigating magnetic exchange within molecular magnets. Herein, the core–shell structure of the monodisperse molecule magnet of [Gd₅₂Ni₅₆(IDA)₄₈(OH)₁₅₄(H₂O)₃₈]@SiO₂ ( 1 a @SiO₂) was prepared by encapsulating one high‐nuclearity lanthanide–transition‐metal compound of [Gd₅₂Ni₅₆(IDA)₄₈(OH)₁₅₄(H₂O)₃₈]?(NO₃)₁₈?164 H₂O ( 1 ) (IDA=iminodiacetate) into one silica nanosphere through a facile one‐pot microemulsion method. 1 a @SiO₂ was characterized using transmission electron microscopy, N₂ adsorption–desorption isotherms, and inductively coupled plasma‐atomic emission spectrometry. Magnetic investigation of 1 and 1 a revealed J₁=0.25 cm^?1, J₂=?0.060 cm^?1, J₃=?0.22 cm^?1, J₄=?8.63 cm^?1, g=1.95, and z J=?2.0×10^?3 cm^?1 for 1 , and J₁=0.26 cm^?1, J₂=?0.065 cm^?1, J₃=?0.23 cm^?1, J₄=?8.40 cm^?1 g=1.99, and z J=0.000 cm^?1 for 1 a @SiO₂. The z J=0 in 1 a @SiO₂ suggests that weak antiferromagnetic coupling between the compounds is shielded by silica nanospheres.     

Metal‐Ion Metathesis in Metal–Organic Frameworks: A Synthetic Route to New Metal–Organic Frameworks

A porous metal–organic framework, Mn(H₃O)[(Mn₄Cl)₃(hmtt)₈] (POST‐65), was prepared by the reaction of 5,5′,10,10′,15,15′‐hexamethyltruxene‐2,7,12‐tricarboxylic acid (H₃hmtt) with MnCl₂ under solvothermal conditions. POST‐65(Mn) was subjected to post‐synthetic modification with Fe, Co, Ni, and Cu according to an ion‐exchange method that resulted in the formation of three isomorphous frameworks, POST‐65(Co/Ni/Cu), as well as a new framework, POST‐65(Fe). The ion‐exchanged samples could not be prepared by regular solvothermal reactions. The complete exchange of the metal ions and retention of the framework structure were verified by inductively coupled plasma–atomic emission spectrometry (ICP‐AES), powder X‐ray diffraction (PXRD), and Brunauer–Emmett–Teller (BET) surface‐area analysis. Single‐crystal X‐ray diffractions studies revealed a single‐crystal‐to‐single‐crystal (SCSC)‐transformation nature of the ion‐exchange process. Hydrogen‐sorption and magnetization measurements showed metal‐specific properties of POST‐65.     

An Ideal Detector Composed of Two‐Dimensional Cd(II)–Triazole Frameworks for Nitro‐Compound Explosives and Potassium Dichromate

The two‐dimensional (2D) metal–organic framework (MOF) [Cd(TPTZ)(H₂O)₂(HCOOH)(IPA)₂]_n ( 1 ; TPTZ={4‐[4‐(1H‐1,2,4‐triazol‐1‐yl)phenyl]phenyl}‐1H‐1,2,4‐triazole, IPA=isophthalic acid) has been constructed with the π‐electron‐rich aromatic ligand TPTZ, auxiliary ligand IPA, and the metal Cd²⁺ ion with a d¹⁰ configuration under solvothermal conditions. Complex 1 exhibits a strong ligand‐originated photoluminescence emission, which is selectively sensitive toward electron‐deficient nitroaromatic compounds, such as nitrobenzene (NB), 1,3‐dinitrobenzene (m‐DNB), and 1,4‐dinitrobenzene (p‐DNB), and nitro‐aliphatic compounds, such as nitromethane (NM) and tris(hydroxymethyl)nitromethane. This property makes complex 1 a potential fluorescence sensor for these chemicals. Single‐crystal X‐ray diffraction studies revealed that dinuclear cadmium building units were further bridged by TPTZ ligands to give a four‐connected uninodal net with the Schläfli symbol of [4.6₃.4.6₃.6₂.6₄].     

Oxidation reactions catalysed by molybdenum(VI) complexes grafted on UiO‐66 metal–organic framework as an elegant nanoreactor

A heterogeneous catalyst was synthesized by immobilizing Mo(CO)₃ in a UiO‐66 metal–organic framework. The benzene ring of the organic linker in UiO‐66 was modified via liquid‐phase deposition of molybdenum hexacarbonyl, Mo(CO)₆, as starting precursor to form the (arene)Mo(CO)₃ species inside the framework. The structure of this catalyst was characterized using X‐ray diffraction, and chemical integrity was confirmed using Fourier transform infrared and diffuse reflectance UV–visible spectroscopic methods. The metal content was analysed with inductively coupled plasma. Field emission scanning electron microscopy was used to measure particle size and N₂ adsorption measurements to characterize the specific surface area. This catalytic system was efficiently applied for epoxidation of alkenes and oxidation of sulfides. The Mo‐containing metal–organic framework was reused several times without any appreciable loss of its efficiency.     

Selective Host–Guest Interaction between Metal Ions and Metal–Organic Frameworks Using Dynamic Nuclear Polarization Enhanced Solid‐State NMR Spectroscopy

The host–guest interaction between metal ions (Pt²⁺ and Cu²⁺) and a zirconium metal–organic framework (UiO‐66‐NH₂) was explored using dynamic nuclear polarization‐enhanced ¹⁵N{¹H} CPMAS NMR spectroscopy supported by X‐ray absorption spectroscopy and density functional calculations. The combined experimental results conclude that each Pt²⁺ coordinates with two NH₂ groups from the MOF and two Cl^? from the metal precursor, whereas Cu²⁺ do not form chemical bonds with the NH₂ groups of the MOF framework. Density functional calculations reveal that Pt²⁺ prefers a square‐planar structure with the four ligands and resides in the octahedral cage of the MOF in either cis or trans configurations.     

A new luminescent anionic metal–organic framework based on heterometallic zinc(II)–barium(II) for selective detection of Fe3+ and Cu2+ ions in aqueous solution

Over the past two decades, the development of novel inorganic–organic hybrid porous crystalline materials or metal–organic frameworks (MOFs) using crystal engineering has provoked significant interest due to their potential applications as functional materials. In this context, luminescent MOFs as fluorescence sensors have recently received significant attention for the sensing of ionic species and small molecules. In this work, a new luminescent heterometallic zinc(II)–barium(II)‐based anionic metal–organic framework, namely poly[imidazolium [triaqua(μ₆‐benzene‐1,3,5‐tricarboxylato)bariumtrizinc] tetrahydrate], {(C₃H₄N₂)[BaZn₃(C₉H₃O₆)₃(H₂O)₃]·4H₂O}_n ( 1 ), was synthesized under hydrothermal conditions and characterized. Compound 1 presents a three‐dimensional framework with an unprecedented (3,5)‐connected topology of the point symbol (3.9²).(3³.4².5.9³.10), and exhibits `turn‐off' luminescence responses for the Cu²⁺ and Fe³⁺ ions in aqueous solution based on significantly different quenching mechanisms.