Tailoring Hybrid Aluminoborate Frameworks by Incorporating Multicomponent Cadmium-Amine Complexes with Various Conformations

Inorganic-organic hybrid aluminoborates represent a subclass of porous materials, which rely on effective construction method and structure-directing agents. Herein, we prepared a series of hybrid aluminoborates through covalent decoration of unsaturated Cd²⁺ complexes, whose formation take advantage of chelating amine and long-chain diamine as mixed ligands. These isolated compounds, that is, [Cd(en)(1,4-dab)_0.5][AlB₅O₁₀] (1a; its analogue with discrete complex [Cd(en)(dien)H₂O][AlB₅O₁₀] is denoted as 1b), [Cd(1,2-dap)_1.5(1,4-dabH)_0.5]{Al[B₅O₈(OH)₂](B₅O₁₀)_0.5} (2), and [Cd(en)(1,3-dap)][AlB₅O₁₀] (3) feature open frameworks (1a, 1b, and 3) or a sandwich-like porous layer (2) that are constructed by AlO₄ tetrahedra and [B₅O₁₀]^5-/[B₅O₈(OH)₂]^3- clusters. However, they exhibit different structural features in interconnection, channel environment, and topology as a result of diversified interactions between unsaturated complexes and aluminoborate frameworks, that is, through forming two Cd-O bonds with (i) a pair of neighboring BO₃ and AlO₄, (ii) the same AlO₄, or (iii) the same BO₃. The variation in connection mode exerts essential influence on binding effects and steric hindrance that are reflected by changes in interatomic distance, bond angle, window configuration, and interlinkage of units. In addition, the incorporation of unsaturated Cd²⁺ complexes endows these aluminoborate materials with photoluminescence function. Compound 3 with a noncentrosymmetric structure exhibits second harmonic generation (SHG) response approximately 0.7 times that of KDP. The preparation strategy for hybrid aluminoborates proposed here combines well molecular design with templating assembly, whose synergistic effect would be crucial for drawing a rational pathway for inorganic synthesis, especially with focus on structural and functional innovation.

Chiral Fluorescent Metal-Organic Framework with a Pentanuclear Copper Cluster as an Efficient Luminescent Probe for Dy3+ Ion and Cyano Compounds

Luminescent probes have been used for the detection of various heavy metals and toxic compounds. A novel sensor with excellent sensitivity and selectivity is in high demand. Herein, we designed and synthesized a three-dimensional copper-organic framework of "pcu" α-Po primitive cubic topology with a Schläfli symbol of {4.4.4.4.4.4.4.4.4.4.4.4.*.*.*}. By taking advantage of metal clusters and a triazole ligand as the metal-organic framework (MOF) components, the newly obtained MOF is stable in various environments and can be potentially used as the sensor. Remarkably, this MOF-based sensor shows high sensitivity and selectivity toward a dysprosium ion (Dy³⁺) in a multiple-lanthanide mixed solution. Besides, it exhibits luminescent quenching toward various cyano compounds. This chiral cluster-based network provides a potential luminescent probe for various inorganic and organic compounds with high sensitivity and selectivity.

SC-SC Anion-Assisted Linker Exchange within a Three-Dimensional Cu(II)-Triazole Framework: A Luminescent Probe for S2

A three-dimensional (3D) binodal 3,5-connected net, {[Cu(MTP)(H2O)](NO3)}n (1) with the Schläfli symbol of {3·72}{32·75·83} can be transformed into a two-dimensional (2D) kagóme network with the Schlafli symbol of {32·62·72} in an irreversible single crystal-single crystal (SC-SC) guest-assisted linker exchange process. The product of this SC-SC represents the first luminescent probe for S2- based on triazole ligand.

Coordination-Bond-Driven Dissolution-Recrystallization Structural Transformation with the Expansion of Cuprous Halide Aggregate

Metal-organic frameworks (MOFs) with cuprous-halide-aggregates have shown superiority as organic LED (OLED) and semiconductor materials, while engineering MOF flexibility by involving the expansion of cuprous aggregates remains a great challenge. In this particular work, a dissolution-recrystallization structural transformation (DRST) with the dramatic growth of Cu^I-I aggregates, from 2D NJNU-100 to 3D NJNU-101 has been successfully realized. The unsaturated coordination nodes (2-positional nitrogen atoms) in NJNU-100 have been demonstrated to be the driven force for DRST to NJNU-101 via the formation of coordination bonds. The structural transformation process was irreversible and observed with optical microscopy and powder XRD. The expansion of Cu^I-I aggregates was also computational simulated accompanying with the rotation of the neutral tripodal TTTMB ligand (1,3,5-tris(1,2,4-triazol-1-ylmethyl)-2,4,6-trimethylbenzene) and the reduction of Cu^II to Cu^I. Moreover, the intermediate product NJNU-102 was captured by adding the planar molecular anthrancene to shut down the reaction, where only partial 2-positional nitrogen atoms coordinated to the aggregates and the anthrancene was oxidized to anthraquinone. NJNU-102 has further confirmed that DRST involved the breakage and recombination of coordination bonds and the electron transfer. NJNU-100 and NJNU-101 could be applied as semiconductor and OLED materials. This work has provided insights for crystal engineering, especially for the construction of the Cu^I_xX_y aggregates, and illustrated that DRST could be controlled with a rational design (as the unsaturated coordination modes).

Interpol review of detection and characterization of explosives and explosives residues 2016-2019

This review paper covers the forensic-relevant literature for the analysis and detection of explosives and explosives residues from 2016-2019 as a part of the 19th Interpol International Forensic Science Managers Symposium. The review papers are also available at the Interpol website at: https://www.interpol.int/Resources/Documents#Publications.

Ligand-Rearrangement-Induced Transformation from a 3D Supramolecular Network to a Discrete Octanuclear Cluster: A Good Detector for Pb2+ and Cr2O7 2

A three-dimensional supramolecular framework containing both left- and right-handed helixes, {[Zn(TTPA)Cl₂]·1.63H₂O} _n (1), has been converted to a novel octanuclear cluster containing a metal-organic framework, [Zn₈(ptptp)₆Cl₂](ClO₄)₂·4CH₃OH·2H₂O (1b), induced by ligand rearrangement during a solvothermal process. The luminescent properties of 1b indicate that the material can act as a selective probe toward Pb²⁺ and Cr₂O₇ ^2-.

A Pillar-Layered Zn-LMOF with Uncoordinated Carboxylic Acid Sites: High Performance for Luminescence Sensing Fe3+ and TNP

By using the mixed-linker strategy, a new pillar-layered luminescence Zn-LMOF (JLU-MOF71) ([Zn₂Na₂(TPHC)(4,4-Bipy)(DMF)]·8H₂O) (TPHC = [1,1':2',1″-terphenyl]-3,3″,4,4',4″,5'-hexacarboxylic acid, 4,4-bipy = 4,4-bipyridine, DMF = N, N-dimethylformamide) was successfully synthesized and structurally characterized. JLU-MOF71 is constructed by the 4,4-bipy pillars and 2D layers which consist of Zn²⁺ and TPHC ligands, and displays a rare fsh topology. Benefiting from the uncoordinated carboxylate sites in the framework, JLU-MOF71 not only can sensitively detect trace amounts of individual Fe³⁺ and 2,4,6-trinitrophenol (TNP) through luminescence quenching but also exhibits high selectivity when other competing analytes exist. Besides, TNP can also be effectively monitored with the help of the shifting direction of luminescent spectra (red shift) which has rarely been reported before. On the basis of the aforementioned, JLU-MOF71 can be considered as a potential luminescence sensor for detecting Fe³⁺ and TNP.

A "turn-on" fluorescent probe for the detection of permanganate in aqueous media

A novel carbazole-based probe was synthesized and found to exhibit fluorescence upon introduction to potassium permanganate in aqueous media. Guided by a series of experimental studies and DFT calculations, the underlying mechanism is proposed to proceed through a series of tandem proton and electron transfer processes.

Solvent-induced SC–SC transformation within the ZnII–triazole system: a promising MnO4− selective luminescent probe

The solvent-induced SC–SC transformation within the Zn^II–triazole system has generated a 3D network containing corrugated ladders of 4a. The luminescence properties indicated that 4a could be considered as a MnO₄⁻ selective luminescent probe.

Zinc(ii)–organic framework as a multi-responsive photoluminescence sensor for efficient and recyclable detection of pesticide 2,6-dichloro-4-nitroaniline, Fe(iii) and Cr(vi)

A stable Zn-MOF acts as a multi-responsive luminescent sensor for efficient and recyclable detection of organochlorine pesticide 2,6-dichloro-4-nitroaniline, Fe(iii) and Cr(vi) with high selectivity and sensitivity.

Adsorption and Detection of Hazardous Trace Gases by Metal-Organic Frameworks

The quest for advanced designer adsorbents for air filtration and monitoring hazardous trace gases has recently been more and more driven by the need to ensure clean air in indoor, outdoor, and industrial environments. How to increase safety with regard to personal protection in the event of hazardous gas exposure is a critical question for an ever-growing population spending most of their lifetime indoors, but is also crucial for the chemical industry in order to protect future generations of employees from potential hazards. Metal-organic frameworks (MOFs) are already quite advanced and promising in terms of capacity and specific affinity to overcome limitations of current adsorbent materials for trace and toxic gas adsorption. Due to their advantageous features (e.g., high specific surface area, catalytic activity, tailorable pore sizes, structural diversity, and range of chemical and physical properties), MOFs offer a high potential as adsorbents for air filtration and monitoring of hazardous trace gases. Three advanced topics are considered here, in applying MOFs for selective adsorption: (i) toxic gas adsorption toward filtration for respiratory protection as well as indoor and cabin air, (ii) enrichment of hazardous gases using MOFs, and (iii) MOFs as sensors for toxic trace gases and explosives.

Four 3D coordination polymers based on layers with single syn-anti carboxylate bridges: synthesis, structures, and magnetic properties

Four novel coordination polymers (CPs) based on a new 4-(3,5-dicarboxylphenyl) picolinic acid ligands (H3L), [M3(L)2(H2O)6]·4H2O (M3 = Mn3, 1; Co3, 2; Ni3, 3, Co1.01Ni1.99, 4), have been hydrothermally synthesized, and structurally and magnetically characterized. In these isomorphous CPs, octahedrally coordinated metal ions are linked by the single syn-anti carboxylate bridge (μ-COO) to give linear trinuclear motifs. The motifs are connected through the other single syn-anti carboxylate bridge (μ-COO) to give a 2D (4,4) layer, and the layers are interlinked by the L ligands into 3D frameworks. Magnetic measurement indicates that antiferromagnetic interactions between metal ions are mediated through the single syn-anti carboxylate bridges in 1 and 2, while the same carboxylate bridges in 3 transmit ferromagnetic couplings. The bimetallic CP 4 shows interesting complicated magnetic behaviors due to the competition effect of Co(ii) and Ni(ii) ions.

Explosives in the Cage: Metal-Organic Frameworks for High-Energy Materials Sensing and Desensitization

An overview of the current status of coordination polymers and metal-organic frameworks (MOFs) pertaining to the field of energetic materials is provided. The explosive applications of MOFs are discussed from two aspects: one for detection of explosives, and the other for explosive desensitization. By virtue of their adjustable pore/cage sizes, high surface area, tunable functional sites, and rich host-guest chemistry, MOFs have emerged as promising candidates for both explosive sensing and desensitization. The challenges and perspectives in these two areas are thoroughly discussed, and the processing methods for practical applications are also discussed briefly.

Anion exchange coupled with the reduction and dimerisation of a copper(ii) nitrate complex of tripyridyl dithioether via a single-crystal-to-single-crystal transformation

It is a challenge to develop methodologies involving multiple transformations for preparing new materials that cannot be obtained via direct synthesis. Herein, we report an anion exchange process accompanying cation reduction and dimerisation via a single-crystal-to-single-crystal transformation. First, a direct reaction of the flexible tripyridyl dithioether ligand L with CuI afforded a mixture of four bis(ligand) complexes (1a-1d). To avoid the formation of undesired mixed products, a copper(ii) nitrate complex-mediated approach involving anion exchange and cation reduction was employed to generate a monomeric complex, [CuII(L)NO3]NO3·toluene (2). When the dark blue crystals of 2 were immersed in an aqueous NaI solution, the crystals were transformed to a pale yellow dimeric copper(i) iodide complex, [(μ-CuI2I2)(L)2] (3). The observed anion exchange promotes the reduction of copper(ii) to copper(i) at the expense of I-/I3- oxidation as well as dimerisation via the formation of a Cu2I2 cluster. This result corresponds to the synthesis of a compound that otherwise was not able to be prepared via a direct synthetic procedure.

Synthesis, structures and magnetic properties of two chiral mixed-valence iron(ii,iii) coordination networks

Two rare chiral mixed-valence iron(ii,iii) coordination networks have been synthesized through spontaneous asymmetrical crystallization from achiral units in the assembly process.