Synthesis and Electrochemical Performance of SnOx Quantum Dots@ UiO-66 Hybrid for Lithium Ion Battery Applications

A novel method that combines the dehydration of inorganic clusters in metal-organic frameworks (MOFs) with nonaqueous sol-gel chemistry and pyrolysis processes is developed to synthesize SnO_x quantum dots@Zr-MOFs (UIO-66) composites. The size of as-prepared SnO_x nanoparticles is approximately 4 nm. Moreover, SnO_x nanoparticles are uniformly anchored on the surface of the Zr-MOFs, which serves as a matrix to alleviate the agglomeration of SnO_x grains. This structure provides an accessible surrounding space to accommodate the volume change of SnO_x during the charge/discharge process. Cyclic voltammetry and galvanostatic charge/discharge were employed to examine the electrochemical properties of the ultrafine SnO_x@Zr-MOF (UIO-66) material. Benefiting from the advantages of the smaller size of SnO_x nanoparticles and the synergistic effect between SnO_x nanoparticles and the Zr-MOFs, the SnO_x@Zr-MOF composite exhibits enhanced electrochemical performance when compared to that of its SnO_x bulk counterpart. Specifically, the discharge-specific capacity of the SnO_x@Zr-MOF electrode can still remain at 994 mA h g^-1 at 50 mA g^-1 after 100 cycles. The columbic efficiencies can reach 99%.

Ultrahigh adsorption and singlet-oxygen mediated degradation for efficient synergetic removal of bisphenol A by a stable zirconium-porphyrin metal-organic framework

Bisphenol A (BPA), one of 23 most important endocrine disrupting chemicals, was efficiently removed and sequentially photodegraded by a zirconium-porphyrin metal–organic framework (MOF) catalyst under visible light for water treatment. Well control of photodegradation allows the kinetic separation of adsorption step and photodegradation step. Ultrahigh adsorption uptake of 487.69 ± 8.37 mg g⁻¹ is observed, while efficient photodegradation could be observed within 20 min at the rate of 0.004 mg min⁻¹. The synergetic effect boosts the photocatalytic efficiency and confirms that the catalysis happens inside the MOF pores other than in the solution phase. Furthermore, the mechanism was elucidated by diverse control experiments, such as in the conditions of ¹O₂ scavenger, in darkness and with the changes of light sensitizing ligands. It confirmed that BPA was oxidized by the ¹O₂ which was generated from porphyrin ligand within MOFs under visible-light. The excellent reusability and wide range of suitable pH range make the Zr-porphyrin MOFs practical for the photocatalytic water treatment processes.

Ultrasonic synthesis of two nanostructured cadmium(II) coordination supramolecular polymers: Solvent influence, luminescence and photocatalytic properties

Two nanoparticles of cadmium(II) coordination polymers (CPs) formulated as [Cd(L)(DCTP)]_n (1) and [Cd(L)₂(DCTP)·2H₂O]_n (2) (L=1,2-bis(2-methylbenzimidazol-1-ylmethyl)benzene, H₂DCTP=2,5-dichloroterephthalic acid) were prepared by the sonochemical approach in different solvents and characterized by elemental analysis, IR spectra, scanning electron microscopy (SEM), and powder X-ray diffraction. Structural determination reveals that CP 1 displays a 2D four-connected sql net layer, Whilst CP 2 exhibits a 1D "V"-like chain structure. Luminescence properties, thermal behavior, and photocatalytic activities of the nanoparticles of CPs 1 and 2 on the degradation of methylene blue were investigated. The photocatalytic mechanism is carried out by introducing t-butyl alcohol (TBA) as a widely used OH scavenger. Furthermore, the influence of solvents, reaction time, and ultrasound irradiation temperature on the morphology and size of the nanostructure CPs 1 and 2 were investigated. The results indicated that an increase of time and ultrasound irradiation temperature decreased the nanostructured size.

Highly Selective Bifunctional Luminescent Sensor toward Nitrobenzene and Cu2+ Ion Based on Microporous Metal-Organic Frameworks: Synthesis, Structures, and Properties

Two metal-organic frameworks (MOFs), namely, [Ni(DTP)(H₂O)]_n (I) and [Cd₂(DTP)₂(bibp)_1.5]_n (II) (H₂DPT = 4'-(4-(3,5-dicarboxylphenoxy) phenyl)-4,2':6',4″-terpyridine; bibp = 1,3-di(1H-imidazol-1-yl)propane), that present structural diversity were solvothermally prepared. Single-crystal X-ray diffraction analysis indicates that they consist of {NiN₂O₄} building units (for I) and {CdO₄N₂} and {CdO₃N₃} building units (for II), which are further linked by multicarboxylate H₂DPT to construct microporous three-dimensional frameworks. The remarkable character of these frameworks is that coordination polymer II demonstrates highly selective and sensitive bifunctional luminescent sensor toward nitrobenzene and Cu²⁺ ion. The fluorescence quenching mechanism of II caused by nitrobenzene is ascribed to electron transfer from electron-rich (II) to electron-deficient nitrobenzene. The result was also evidenced by the density functional theory. Furthermore, anti-ferromagnetic as well as electrochemical characters of Ni-MOF (I) were also investigated in this paper.

Porous Zirconium-Furandicarboxylate Microspheres for Efficient Redox Conversion of Biofuranics

Biofuranic compounds, typically derived from C₅ and C₆ carbohydrates, have been extensively studied as promising alternatives to chemicals based on fossil resources. The present work reports the simple assembly of biobased 2,5-furandicarboxylic acid (FDCA) with different metal ions to prepare a range of metal-FDCA hybrids under hydrothermal conditions. The hybrid materials were demonstrated to have porous structure and acid-base bifunctionality. Zr-FDCA-T, in particular, showed a microspheric structure, high thermostability (ca. 400 °C), average pore diameters of approximately 4.7 nm, large density, moderate strength of Lewis-base/acid centers (ca. 1.4 mmol g^-1 ), and a small number of Brønsted-acid sites. This material afforded almost quantitative yields of biofuranic alcohols from the corresponding aldehydes under mild conditions through catalytic transfer hydrogenation (CTH). Isotopic ¹ H NMR spectroscopy and kinetic studies verified that direct hydride transfer was the dominant pathway and rate-determining step of the CTH. Importantly, the Zr-FDCA-T microspheres could be recycled with no decrease in catalytic performance and little leaching of active sites. Moreover, good yields of C₅ (i.e., furfural) or C₄ products [i.e., maleic acid and 2(5H)-furanone] could be obtained from furfuryl alcohol without oxidation of the furan ring over these metal-FDCA hybrids. The content and ratio of Lewis-acid/base sites were demonstrated to dominantly affect the catalytic performance of these redox reactions.

The Influence of Intrinsic Framework Flexibility on Adsorption in Nanoporous Materials

For applications of metal–organic frameworks (MOFs) such as gas storage and separation, flexibility is often seen as a parameter that can tune material performance. In this work we aim to determine the optimal flexibility for the shape selective separation of similarly sized molecules (e.g., Xe/Kr mixtures). To obtain systematic insight into how the flexibility impacts this type of separation, we develop a simple analytical model that predicts a material’s Henry regime adsorption and selectivity as a function of flexibility. We elucidate the complex dependence of selectivity on a framework’s intrinsic flexibility whereby performance is either improved or reduced with increasing flexibility, depending on the material’s pore size characteristics. However, the selectivity of a material with the pore size and chemistry that already maximizes selectivity in the rigid approximation is continuously diminished with increasing flexibility, demonstrating that the globally optimal separation exists within an entirely rigid pore. Molecular simulations show that our simple model predicts performance trends that are observed when screening the adsorption behavior of flexible MOFs. These flexible simulations provide better agreement with experimental adsorption data in a high-performance material that is not captured when modeling this framework as rigid, an approximation typically made in high-throughput screening studies. We conclude that, for shape selective adsorption applications, the globally optimal material will have the optimal pore size/chemistry and minimal intrinsic flexibility even though other nonoptimal materials’ selectivity can actually be improved by flexibility. Equally important, we find that flexible simulations can be critical for correctly modeling adsorption in these types of systems.

Thrombin aptasensor enabled by Pt nanoparticles-functionalized Co-based metal organic frameworks assisted electrochemical signal amplification

In this work, a Pt nanoparticles-functionalized Co-based metal organic frameworks (PtNPs@Co(II)MOFs@PtNPs) was synthesized and applied in electrochemical aptasensor for thrombin (TB) detection. First, the Co(II)MOFs@PtNPs were prepared via the mixed solvothermal method, which consists of inner Pt nanoparticles (PtNPs) encapsulated by aminofunctionalized Co(II)MOFs materials. Following that, additional PtNPs were adsorbed on the surface of Co(II)MOFs@PtNPs, resulting in the formation of PtNPs@Co(II)MOFs@PtNPs nanocomposite. The PtNPs@Co(II)MOFs@PtNPs nanocomposites with a large surface area were implimented as nanocarriers to immobilize a mass of TBA II for the formation of the TBA II bioconjugates that could be captured onto the electrode surface by sandwich-type format. Moreover, the PtNPs@Co(II)MOFs@PtNPs nanocomposites could directly use as redox tags for charge-generating and electron-transporting with the electron transfer from Co(II) to Co(III). Furthermore, in the presence of H₂O₂, the PtNPs@Co(II)MOF@PtNPs could effectively catalyze H₂O₂ oxidation with improvement electron transfer of redox probe, resulting in electrochemical signal amplification. Based on the above superior advantages, TB was determined in the concentration range from 0.1pM to 50nM with a detection limit of 0.33fM. Furthermore, the excellent sensitivity and selectivity can be easily established for quantitative analysis of other analytes.

Dynamic behaviours of a rationally prepared flexible MOF by postsynthetic modification of ligand struts

Through postsynthetic modification of ligand struts, controllable conversion of a Zr MOF between rigidity and flexibility is realized. The rationally prepared flexible MOF exhibits interesting dynamic behaviours, such as reversible structural deformation, vapour sorption hysteresis and unexpected adsorption of bulky guest molecules.

Orderly Layered Zr-Benzylphosphonate Nanohybrids for Efficient Acid-Base-Mediated Bifunctional/Cascade Catalysis

The development of functional metal-organic materials that are robust and active for bifunctional/cascade catalysis is of great significance. Herein, a series of mesoporous and orderly layered nanohybrids were synthesized for the first time through simple and template-free assembly of ortho-, meta-, or para-xylylenediphosphonates (o-, p-, or m-PhP) containing zirconium. It was found that m-PhPZr nanoparticles (20-50 nm) with mesopores centered at 7.9 nm and high Lewis acid-base site ratio (1:0.7) showed excellent performance under mild conditions (as low as 82 °C) in transfer hydrogenation of carbonyl compounds, including bioaldehydes and alcohols, with near quantitative yields and little Zr leaching. Isotopic labeling studies indicated the occurrence of direct hydrogen transfer rather than metal hydride route by bifunctional catalysis. Lewis acidic (Zr) and basic (PO₃ ) centers of the heterogeneous catalyst were further revealed to play a synergistic role in one-pot cascade transformations, for example, of ethyl levulinate to γ-valerolactone and glucose to 5-hydroxymethylfurfural.

Nano Metal-Organic Framework-Derived Inorganic Hybrid Nanomaterials: Synthetic Strategies and Applications

Nano- (or micro-scale) metal-organic frameworks (NMOFs), also known as coordination polymer particles (CPPs), have received much attention because of their structural diversities and tunable properties. Besides the direct use, NMOFs can be alternatively used as sacrificial templates/precursors for the preparation of a wide range of hybrid inorganic nanomaterials in straightforward and controllable manners. Distinct advantages of using NMOF templates are correlated to their structural and functional tailorability at molecular levels that is rarely acquired in any other conventional template/precursor. In addition, NMOF-derived inorganic nanomaterials with distinct chemical and physical properties are inferred to dramatically expand the scope of their utilization in many fields. In this review, we aim to provide readers with a comprehensive summary of recent progress in terms of synthetic approaches for the production of diverse inorganic hybrid nanostructures from as-synthesized NMOFs and their promising applications.

Statistical mechanical model of gas adsorption in porous crystals with dynamic moieties

Some nanoporous, crystalline materials possess dynamic constituents, for example, rotatable moieties. These moieties can undergo a conformation change in response to the adsorption of guest molecules, which qualitatively impacts adsorption behavior. We pose and solve a statistical mechanical model of gas adsorption in a porous crystal whose cages share a common ligand that can adopt two distinct rotational conformations. Guest molecules incentivize the ligands to adopt a different rotational configuration than maintained in the empty host. Our model captures inflections, steps, and hysteresis that can arise in the adsorption isotherm as a signature of the rotating ligands. The insights disclosed by our simple model contribute a more intimate understanding of the response and consequence of rotating ligands integrated into porous materials to harness them for gas storage and separations, chemical sensing, drug delivery, catalysis, and nanoscale devices. Particularly, our model reveals design strategies to exploit these moving constituents and engineer improved adsorbents with intrinsic thermal management for pressure-swing adsorption processes.

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.

Design of a flexible organometallic tecton: host–guest chemistry with picric acid and self-assembly of platinum macrocycles

A new “flexible” and ditopic Pt(ii) organometallic compound is a tecton for the self-assembly of neutral metallacycles. It also exhibits significant binding affinity for picric acid.

Two hybrid transition metal triphosphonates decorated with a tripodal imidazole ligand: synthesis, structures and properties

Two transition-metal triphosphonates with pillar-layered structures were synthesized and characterized. The luminescence, magnetic and proton conductive properties were investigated.

Unravelling chromism in metal–organic frameworks

Chromophoric MOFs are reviewed, focussing on those which change colour on application of external stimuli such as heat, pressure, light or chemical environment.

Multifunctional metal–organic framework catalysts: synergistic catalysis and tandem reactions

Various active sites incorporated into metal–organic frameworks (MOFs) are suitable for synergistic catalysis and tandem reactions.

Coordination polymers from a flexible alkyldiamine-derived ligand

A traditionally good chelating motif, propanediamine, has been incorporated into a robust coordination framework with vacant amine sites.

Fabrication of a new metal–organic framework for sensitive sensing of nitroaromatics and efficient dye adsorption

Theoretical calculations indicate that the luminescence quenching in 1 in the presence of NACs can be attributed to an electron and resonance energy transfer between the MOF 1 and nitro analytes.

Luminescent sulfonate coordination polymers: synthesis, structural analysis and selective sensing of nitroaromatic compounds

Enhanced fluorescence intensity of sulfonate coordination polymers on addition of picric acid.

A porous copper–organic framework with intersecting channels and gas adsorption properties

Integration of [CuI2I₂] and [CuII2(COO)₄(H₂O)₂] clusters produces a porous copper–organic framework, exhibiting high H₂ uptake capacity and excellent adsorption selectivity for CO₂ over N₂ and CH₄.