Continuous MOF Membrane-Based Sensors via Functionalization of Interdigitated Electrodes

Three M-MOF-74 (M = Co, Mg, Ni) metal-organic framework (MOF) thin film membranes have been synthesized through a sensor functionalization method for the direct electrical detection of NO₂. The two-step surface functionalization procedure on the glass/Pt interdigitated electrodes resulted in a terminal carboxylate group, with both steps confirmed through infrared spectroscopic analysis. This surface functionalization allowed the MOF materials to grow largely in a uniform manner over the surface of the electrode forming a thin film membrane over the Pt sensing electrodes. The growth of each membrane was confirmed through scanning electron microscopy (SEM) and X-ray diffraction analysis. The Ni and Mg MOFs grew as a continuous but non-defect free membrane with overlapping polycrystallites across the glass surface, whereas the Co-MOF-74 grew discontinuously. To demonstrate the use of these MOF membranes as an NO₂ gas sensor, Ni-MOF-74 was chosen as it was consistently fabricated as the best thin and homogenous membrane, as confirmed by SEM. The membrane was exposed to 5 ppm NO₂ and the impedance magnitude was observed to decrease 123× in 4 h, with a larger change in impedance and a faster response than the bulk material. Importantly, the use of these membranes as a sensor for NO₂ does not require them to be defect-free, but solely continuous and overlapping growth.

Alkali and alkaline earth coordination polymers constructed from benzene-1,2,4,5-tetracarboxylic acid and flexible dicarboxylate acid ligands: syntheses, structures and spectroscopic and thermal properties

Two new metal coordination complexes, namely, poly[aqua(μ₆-benzene-1,2,4,5-tetracarboxylic acid-κ⁸O¹:O¹,O²:O^2':O⁴:O⁴,O⁵:O^5')(μ-but-2-enedioato-κ²O¹:O⁴)potassium(I)], [K₂(C₄H₂O₄)(C₁₀H₆O₈)(H₂O)₂]_n or [K₂(fum)(H₄btec)(H₂O)₂]_n, (1), and poly[aqua(μ₈-2,5-dicarboxybenzene-1,4-dicarboxylato-κ¹²O¹:O^1',O²:O²,O^2':O^2':O⁴:O^4',O⁵:O⁵,O^5':O^5')(μ-ethanedioato-κ⁴O¹,O²:O^1',O^2')strontium(II)], [Sr₂(C₂O₄)(C₁₀H₄O₈)(H₂O)₂]_n or [Sr₂(ox)(H₂btec)(H₂O)₂]_n, (2) (H₄btec = benzene-1,2,4,5-tetracarboxylic acid, H₂btec = 2,5-dicarboxybenzene-1,4-dicarboxylate, fum = fumarate and ox = oxalate), have been obtained under hydrothermal conditions by reacting the different alkali and alkaline earth metal salts with H₄btec, fumaric acid (H₂fum) and oxalic acid (H₂ox). Complexes (1) and (2) were structurally characterized by single-crystal X-ray diffraction, IR and UV-Vis spectroscopy, powder X-ray diffraction (PXRD) and thermogravimetic analysis-differential scanning calorimetry (TGA-DSC). Complex (1) displays a two-dimensional (2D) layer with the K⁺ ion in a distorted pentagonal bipyramidal geometry and exhibits a uninodal 6-connected hxl/Shubnikov plane net (3,6) with {3⁶.4⁶.5³} topology. Complex (2) displays a three-dimensional (3D) network structure, in which the Sr²⁺ ion is in a distorted monocapped square antiprism geometry. The framework possess a binodal (5,8)-connected net with the Schläfli symbol {3².4¹⁰.5⁸.6⁴.7⁴}{3².4⁶.5²}₂. The 3D Hirshfeld surfaces and 2D fingerprint plots show that the main interactions are the O...H/H...O intermolecular interactions. Moreover, the thermal decompositions of (1) and (2) in the temperature range 303-1273 K revealed that they both decompose in three steps and transform to the corresponding metal oxide.

Construction of thermally robust and porous shrimp ferritin crystalline for molecular encapsulation through intermolecular arginine-arginine attractions

Protein colloid crystals are considered as high porous soft materials, presenting great potentials in nutrients and drug encapsulation, but protein crystal fabrication usually needs precipitant and high protein concentration. Herein, an easy implemented approach was reported for the construction of protein colloid crystals in diluted solution with shimp ferritin as building blocks by taking advantage of the strength of multiple intermolecular arginine-arginine interactions. The X-ray single-crystal structure reveals that a group of exquisite arginine-arginine interactions between two neighboring ferritin enable them self-assembly into long-range ordered protein soft materials. The arginine-arginine interactions mediate crystal generation favored at pH 9.5 with 200 mM NaCl, and the resulting colloid crystals exhibit high thermal stability (90 °C for 30 min). Importantly, the interglobular cavity in colloid crystals is three times larger in volume than that of intrinsic ferritin cavity in each unit cell, which can be used for molecular encapsulation.

Centimeter-Scale Pillared-Layer Metal-Organic Framework Thin Films Mediated by Hydroxy Double Salt Intermediates for CO2 Sensor Applications

Fabrication of metal-organic framework (MOF) thin films over macroscopic surface areas is a subject of great interest for gas sensor application platforms such as optics and microelectronics. However, a direct synthesis of MOF films at ambient conditions, in particular pillared-layer MOF films due to their anisotropic structures, remains a significant challenge. Herein, we demonstrate for the first time a facile construction of dense and continuous pillared-layer MOF thin films on a centimeter scale via an aluminum-doped zinc oxide template and hydroxy double salt (HDS) intermediates at room temperature. A series of Cu(II)-based pillared MOFs with different 1,4-benzenedicarboxylic acid (bdc) ligands were explored for optimizing MOF film formation for CO₂ sensor applications. Nonpolar ligands with lower water solubility preferentially formed crystalline pillared MOF structures from HDS intermediates. A Cu₂(ndc)₂(dabco) (ndc = 1,4-naphthalene-bdc; dabco = 1,4-diazabicyclo[2.2.2]octane) MOF demonstrated the most dense and uniform film growth with micrometer thickness over one square centimeter area. This synthetic approach for growing Cu₂(ndc)₂(dabco) MOF thin films was successfully translated toward two sensing platforms: a quartz crystal microbalance and an optical fiber sensor. These Cu₂(ndc)₂(dabco) MOF-coated sensors displayed sensitivity toward CO₂ and response/recovery time on the scale of seconds, even at moderate humidity levels. This work provides a road map for producing continuous and anisotropic crystalline MOF thin films over a centimeter scale area on various substrates, which will greatly facilitate their utilization in MOF-based sensor devices, among other applications.

A water-stable photochromic MOF with controllable iodine sorption and efficient removal of dichromate

A photochromic cationic MOF with one-dimensional channels was prepared based on a π-conjugated electron-deficient viologen, which exhibits high uptake capacity for Cr2O72− through ion-exchange and controllable iodine adsorption behavior.

Synthesis, structure, and heterogeneous Fenton reaction of new Cu(ii)-based discrete Cu2x coordination complexes

Cu₂L₄ cage and Cu₂L₂ macrocycle were obtained and the heterogeneous Fenton reaction experiments showed that they are good photocatalysts in the photocatalytic degradation process of MB with using hydroxyl radicals and high-valence copper ions.

MOF-on-MOF Membrane with Cascading Functionality for Capturing Dichromate Ions and p-Arsanilic Acid Turn-On Sensing

It is very significant that functional porous metal-organic frameworks are used to manufacture hierarchical components to achieve cascading functions that cannot be achieved by a single-layer metal-organic framework (MOF). Here, we report two cases of novel MOFs constructed by the same ligand, Cu(I)-tpt and Cu(II)-tpt (Htpt = 5-[4(1H-1,2,4-triazol-1-yl)]phenyl-2H-tetrazole), and prepared a Cu(II)-tpt-on-Cu(I)-tpt membrane by a layer-by-layer approach ignoring the lattice mismatch problem. The first Cu(I)-tpt layer is grown on an oriented Cu₂O nanostructured array by a "one-pot" approach. The aligned second Cu(II)-tpt layer can be deposited using liquid-phase epitaxy. Notably, the prepared Cu(II)-tpt-on-Cu(I)-tpt membrane combines adsorption and fluorescence sensing, which exhibited significant adsorption for Cr₂O₇^2- (203.25 mg g^-1) as typical highly poisonous ions with a fluorescence quenching response. Hence, based on the oxidation-reduction between Cr₂O₇^2- and p-arsanilic acid (p-ASA), the Cu(II)-tpt-on-Cu(I)-tpt membrane's ability to adsorb Cr₂O₇^2- could be used to design "on-off-on" mode fluorescence probes to detect p-ASA with high sensitivity (limit of detection (LOD) = 0.0556 μg L^-1). p-ASA can be degraded into highly toxic inorganic arsenic compounds in the natural environment and has received widespread attention. Therefore, the integration of adsorption and fluorescence properties makes the Cu(II)-tpt-on-Cu(I)-tpt membrane a feasible multifunctional material for pollution control and detection.

Polynomials of Degree-Based Indices of Metal-Organic Networks

AIM AND OBJECTIVE

Metal-organic network (MON) is a special class of molecular compounds comprising of groups or metal ion and carbon-based ligand. These chemical compounds are examined employing one, two- or threedimensional formation of porous ore and subfamilies of polymers. Metal-organic networks are frequently utilized in catalysis for the parting & distillation of different gases and by means of conducting solid or super-capacitor. In various scenarios, the compounds are observed balanced in the procedure of deletion or diluter of the molecule and can be rebuilt with another molecular compound. The physical solidity and mechanical characteristics of the metal-organic network have attained great attention due to the mention properties. This study was undertaken to find the polynomials of MON.

METHODS

Topological descriptor is a numerical number that is utilized to predict the natural correlation amongst the physico-chemical properties of the molecular structures in their elementary networks.

RESULTS

After partitioning the vertices based on their degrees, we calculate different degree-based topological polynomials for two distinct metal-organic networks with an escalating number of layers containing both metals and carbon-based ligand vertices.

CONCLUSION

In the analysis of the metal-organic network, topological descriptors and their polynomials play an important part in modern chemistry. An analysis between the calculated various forms of the polynomials and topological descriptors through the numeric values and their graphs is also comprised.

Multifunctional metal-organic frameworks in oil spills and associated organic pollutant remediation

The release of toxic organic compounds into the environment in an event of oil spillage is a global menace due to the potential impacts on the ecosystem. Several approaches have been employed for oil spills clean-up, with adsorption technique proven to be more promising for the total reclamation of a polluted site. Of the several adsorbents so far reported, adsorbent-based porous materials have gained attention for the reduction/total removal of different compounds in environmental remediation applications. The superior potential of mesoporous materials based on metal-organic frameworks (MOFs) against conventional adsorbents is due to their intriguing and enhanced properties. Therefore, this review presents recent development in MOF composites; methods of preparation; and their practical applications towards remediating oil spill, organic pollutants, and toxic gases in different environmental media, as well as potential materials in the possible deployment in reclaiming the polluted Niger Delta due to unabated oil spillage and gas flaring.

Architectural and catalytic aspects of designer materials built using metalloligands of pyridine-2,6-dicarboxamide based ligands

This perspective presents the design, synthesis and crystal structures of a large number of architectures constructed using assorted metalloligands of pyridine-2,6-dicarboxamide based ligands. The metalloligands offered various appended functional groups, whereas design strategies included varying both their position and number. A combination of these parameters resulted in the development of assorted architectures including discrete trinuclear and tetranuclear complexes as well as 1D/2D/3D coordination polymers. The metalloligand strategy not only assisted in the construction of ordered crystalline materials with varied dimensionalities but also judiciously allowed the incorporation of Lewis acidic and redox-active secondary metals in the resultant architectures. As a result, such designer architectures illustrated their noteworthy role both as homogenous and heterogeneous catalysts in different organic transformation reactions.

Electrochemical Applications of Ferrocene-Based Coordination Polymers

Ferrocene and its derivatives, especially ferrocene-based coordination polymers (Fc-CPs), offer the benefits of high thermal stability, two stable redox states, fast electron transfer, and excellent charge/discharge efficiency, thus holding great promise for electrochemical applications. Herein, we describe the synthesis and electrochemical applications of Fc-CPs and reveal how the incorporation of ferrocene units into coordination polymers containing other metals results in unprecedented properties. Moreover, we discuss the usage of Fc-CPs in supercapacitors, batteries, and sensors as well as further applications of these polymers, for example in electrocatalysts, water purification systems, adsorption/storage systems.

In Situ Spectroscopy of Calcium Fluoride Anchored Metal-Organic Framework Thin Films during Gas Sorption

Surface‐mounted metal–organic frameworks (SURMOFs) show promising behavior for a manifold of applications. As MOF thin films are often unsuitable for conventional characterization techniques, understanding their advantageous properties over their bulk counterparts presents a great analytical challenge. In this work, we demonstrate that MOFs can be grown on calcium fluoride (CaF₂) windows after proper functionalization. As CaF₂ is optically (in the IR and UV/Vis range of the spectrum) transparent, this makes it possible to study SURMOFs using conventional spectroscopic tools typically used during catalysis or gas sorption. Hence, we have measured HKUST‐1 during the adsorption of CO and NO. We show that no copper oxide impurities are observed and also confirm that SURMOFs grown by a layer‐by‐layer (LbL) approach possess Cu⁺ species in paddlewheel confirmation, but 1.9 times less than in bulk HKUST‐1. The developed methodology paves the way for studying the interaction of any adsorbed gases with thin films, not limited to MOFs, low temperatures, or these specific probe molecules, pushing the boundaries of our current understanding of functional porous materials.

Growth of Crystalline Bimetallic Metal-Organic Framework Films via Transmetalation

Crystalline films of the Cu₃(BTC)₂ (BTC^3- = 1,3,5-benzenetricarboxylate) metal-organic framework (MOF) have been grown by dip-coating an alumina/Si(111) substrate in solutions of Cu(II) acetate and the organic linker H₃BTC. Atomic force microscopy (AFM) experiments demonstrate that the substrate is completely covered by the MOF film, while grazing incidence wide-angle X-ray scattering (GIWAXS) establishes the crystallinity of the films. Forty cycles of dip-coating results in a film that is ∼70 nm thick with a root mean squared roughness of 25 nm and crystallites ranging from 50-160 nm in height. Co²⁺ ions were exchanged into the MOF framework by immersing the Cu₃(BTC)₂ films in solutions of CoCl₂. By varying the temperature and exchange times, different concentrations of Co were incorporated into the films, as determined by X-ray photoelectron spectroscopy experiments. AFM studies showed that morphologies of the bimetallic films were largely unchanged after transmetalation, and GIWAXS indicated that the bimetallic films retained their crystallinity.

Surface Modifications of Nanofillers for Carbon Dioxide Separation Nanocomposite Membrane

CO2 separation is an important process for a wide spectrum of industries including petrochemical, refinery and coal-fired power plant industries. The membrane-based process is a promising operation for CO2 separation owing to its fundamental engineering and economic benefits over the conventionally used separation processes. Asymmetric polymer–inorganic nanocomposite membranes are endowed with interesting properties for gas separation processes. The presence of nanosized inorganic nanofiller has offered unprecedented opportunities to address the issues of conventionally used polymeric membranes. Surface modification of nanofillers has become an important strategy to address the shortcomings of nanocomposite membranes in terms of nanofiller agglomeration and poor dispersion and polymer–nanofiller incompatibility. In the context of CO2 gas separation, surface modification of nanofiller is also accomplished to render additional CO2 sorption capacity and facilitated transport properties. This article focuses on the current strategies employed for the surface modification of nanofillers used in the development of CO2 separation nanocomposite membranes. A review based on the recent progresses made in physical and chemical modifications of nanofiller using various techniques and modifying agents is presented. The effectiveness of each strategy and the correlation between the surface modified nanofiller and the CO2 separation performance of the resultant nanocomposite membranes are thoroughly discussed.

MOF-Based Membranes for Gas Separations

Metal-organic frameworks (MOFs) represent the largest known class of porous crystalline materials ever synthesized. Their narrow pore windows and nearly unlimited structural and chemical features have made these materials of significant interest for membrane-based gas separations. In this comprehensive review, we discuss opportunities and challenges related to the formation of pure MOF films and mixed-matrix membranes (MMMs). Common and emerging separation applications are identified, and membrane transport theory for MOFs is described and contextualized relative to the governing principles that describe transport in polymers. Additionally, cross-cutting research opportunities using advanced metrologies and computational techniques are reviewed. To quantify membrane performance, we introduce a simple membrane performance score that has been tabulated for all of the literature data compiled in this review. These data are reported on upper bound plots, revealing classes of MOF materials that consistently demonstrate promising separation performance. Recommendations are provided with the intent of identifying the most promising materials and directions for the field in terms of fundamental science and eventual deployment of MOF materials for commercial membrane-based gas separations.

Surface-coordinated metal-organic framework thin films (SURMOFs) for electrocatalytic applications

The design and development of highly efficient electrocatalysts are very important in energy storage and conversion. As a kind of inorganic organic hybrid material, metal-organic frameworks (MOFs) have been used as electrocatalysts in electrocatalytic reactions due to their structural diversities and fascinating functionalities. Particularly, MOF thin films are coordinated on substrate surfaces by a liquid phase epitaxial (LPE) layer by layer (LBL) growth method (called surface-coordinated MOF thin films, SURMOFs), and recently have been studied in various applications due to their precisely controlled thickness, preferred growth orientation and homogeneous surface. In this review, we will summarize the preparation and electrocatalysis of SURMOFs and their derived thin films (SURMOF-D). The SURMOF based thin films possess diverse topological structures and flexible properties, providing abundant catalytically active sites and fast charge transfer for efficient electrocatalytic performance in the oxygen evolution reaction (OER), oxygen reduction reaction (ORR), hydrogen evolution reaction (HER), carbon dioxide reduction reaction (CRR), supercapacitors, tandem electrocatalysis and so on. The research challenges and problems of SURMOFs for electrocatalytic applications are also discussed at the end of the review.

Enhanced proton conductivity in a layered coordination polymer

[Gd(H₄nmp)(H₂O)₂]Cl·2H₂O (1) converts into [Gd₂(H₃nmp)₂]·xH₂O (2) (x = 1 to 4) with a notable increase in proton conductivity.

[Gd(H₄nmp)(H₂O)₂]Cl·2H₂O (1) converts into [Gd₂(H₃nmp)₂]·xH₂O (2) (x = 1 to 4) with a notable increase in proton conductivity. 1 is a charged layered material counter balanced by chloride ions, with proton conductivity values of 1.23 × 10^–5 S cm^–1 at 98% relative humidity (RH) and 40 °C. At 98% RH and 94 °C the observed conductivity is 0.51 S cm^–1, being to date one of the highest values ever reported for a proton-conducting coordination polymer. This increase is observed during a structural transformation into 2 that occurs at high temperature and RH. While this remarkable conductivity is observed only after transformation and by maintaining high humidity conditions, as-synthesized 2 also shows a conductivity value of 3.79 × 10^–2 S cm^–1 at 94 °C and 98% RH, still ranked as one of the highest reported values. Moreover, it is shown that the key factor for high proton conduction is the unusual dynamic structural transformation with water insertion and release of chloride ions.

Polycrystalline Advanced Microporous Framework Membranes for Efficient Separation of Small Molecules and Ions

Advanced porous framework membranes with excellent selectivity and high permeability of small molecules and ions are highly desirable for many important industrial separation applications. There has been significant progress in the fabrication of polycrystalline microporous framework membranes (PMFMs) in recent years, such as metal-organic framework and covalent organic framework membranes. These membranes possess small pore sizes, which are comparable to the kinetic diameter of small molecules and ions on the angstrom scale, very low thickness, down to tens to hundreds of nanometers, highly oriented crystalline structures, hybrid membrane structures, and specific functional groups for enhancing membrane selectivity and permeability. Recent advances in the fabrication methods of advanced PMFMs are summarized. Following this, four emerging separation applications of these advanced microporous framework membranes, including gas separation, water desalination, ion separation, and chiral separation, are highlighted and discussed in detail. Finally, a summary and some perspectives of future developments and challenges in this exciting research field are presented.

Regulating Hydrogenation Chemoselectivity of α,β-Unsaturated Aldehydes by Combination of Transfer and Catalytic Hydrogenation

Two hydrogenation mechanisms, transfer and catalytic hydrogenation, were combined to achieve higher regulation of hydrogenation chemoselectivity of cinnamyl aldehydes. Transfer hydrogenation with ammonia borane exclusively reduced C=O bonds to get cinnamyl alcohol, and Pt-loaded metal-organic layers efficiently hydrogenated C=C bonds to synthesize phenyl propanol with almost 100 % conversion rate. The hydrogenation could be performed under mild conditions without external high-pressure hydrogen and was applicable to various α,β-unsaturated aldehydes.

Metal–Organic Framework Thin Films: Fabrication, Modification, and Patterning

Metal–organic frameworks (MOFs) have been of great interest for their outstanding properties, such as large surface area, low density, tunable pore size and functionality, excellent structural flexibility, and good chemical stability. A significant advancement in the preparation of MOF thin films according to the needs of a variety of applications has been achieved in the past decades. Yet there is still high demand in advancing the understanding of the processes to realize more scalable, controllable, and greener synthesis. This review provides a summary of the current progress on the manufacturing of MOF thin films, including the various thin-film deposition processes, the approaches to modify the MOF structure and pore functionality, and the means to prepare patterned MOF thin films. The suitability of different synthesis techniques under various processing environments is analyzed. Finally, we discuss opportunities for future development in the manufacturing of MOF thin films.

Superwetting Oil/Water Separation Membrane Constructed from In Situ Assembled Metal-Phenolic Networks and Metal-Organic Frameworks

Superwetting membranes with opposite wettability to oil and water have drawn intense attention in recent years for oil/water separation. Superhydrophilic and underwater superoleophobic membranes have shown unique advantages in the efficient treatment of oily wastewater containing oil-in-water emulsions. Facile interfacial engineering and microstructural design of the hierarchical architectures and the hydrophilic chemistry is of significance but still challenging. In this study, a hydrophilic hierarchical hybrid layer derived from metal-phenolic network (MPN)/metal-organic framework (MOF) synergy is constructed on the membrane surface via a proposed coordination-directed alternating assembly strategy. The assembly of MPN multilayers provides a hydrophilic chemical basis, and the assembly of MOF nanocrystals provides a hierarchical structural basis. Notably, the coordination interfacial interaction enables the formation of well-defined hydrophilic hierarchical architectures. The obtained membrane is thus endowed with robust superhydrophilicity, underwater superoleophobicity, and anti-oil-adhesion capability, which make it capable of highly efficient oil-water separation with high water permeance (above 6300 L/m² h), high oil rejection (above 99.4%), and recyclable antifouling property. The high performance of the developed superwetting membrane makes it a competitive candidate for oil/water separation. Additionally, the demonstrated MPN/MOF assembly strategy may offer new prospects for the facile and versatile design of other superwetting materials.

Highly Stable and Rapid Switching Electrochromic Thin Films Based on Metal-Organic Frameworks with Redox-Active Triphenylamine Ligands

Metal-organic frameworks (MOFs), known for their tailorable porous structures and large specific surface areas, are appealing for electrochromic applications as their abundant pores may greatly benefit the charge transport required for electrochromic switching. Herein, for the first time, a simple, scalable, and cost-effective electrochemical deposition method for fabrication of high-performance and durable MOFs-based electrochromic films with redox-active ligands was developed. The fabricated film can achieve rapid switching speed (both coloration and bleaching time <5 s) because the inherent cavities of the MOFs greatly facilitate ion insertion and extraction. In addition, the film constructed with optimized parameters shows a high optical contrast of 65%@700 nm and can be stably switched for 1000 cycles with <5% contrast attenuation, which is by far the best cycling performance for MOFs-based electrochromic materials ever reported. Furthermore, our method enables the scalable preparation of large-area MOFs-based electrochromic thin films without using large high-pressure reaction vessels, and the as-prepared film in this work could be switched well between colored and bleached states. This new method, therefore, opens up a new avenue to broaden the use of MOFs-based thin films for electrochromic applications.

Spectroscopy, microscopy, diffraction and scattering of archetypal MOFs: formation, metal sites in catalysis and thin films

A comprehensive overview of characterization tools for the analysis of well-known metal–organic frameworks and physico-chemical phenomena associated to their applications.

A highly stable 8-hydroxyquinolinate-based metal–organic framework as a selective fluorescence sensor for Fe3+, Cr2O72− and nitroaromatic explosives

A novel 8-hydroxyquinolinate-based metal–organic framework exhibits excellent sensing performance toward Fe³⁺, Cr₂O₇²⁻ and nitroaromatic explosives.

Controlling the morphology of metal–organic frameworks and porous carbon materials: metal oxides as primary architecture-directing agents

We give a comprehensive overview of how the morphology control is an effective and versatile way to control the physicochemical properties of metal oxides that can be transferred to metal–organic frameworks and porous carbon materials.

Formation of Metal-Organic Frameworks on a Metal Ion-Doped Polymer Substrate: In-Depth Time-Course Analysis Using Scanning Electron Microscopy

The growth of metal-organic frameworks (MOFs) on a metal ion-doped polymer as a precursor and support substrate was investigated based on mechanistic and kinetic analyses. The studies were performed by varying the reaction temperature and the concentrations of the organic ligand and nucleation-promoted additive. Using the NH₂-MIL-53(Al) framework as a model system, a systematic study of the mechanism of formation of tetragonal- and rod-shaped NH₂-MIL-53(Al) crystals on the substrate was performed. The nucleation rate in the early stage of the reaction is a major factor in determining the surface morphology of the resultant NH₂-MIL-53(Al) crystal films, as confirmed by changing the concentration of organic ligands and by employing pyridine additives. These results provide a fundamental understanding of the influence of the nucleation rate on the ability to control the morphology and structure of MOF crystal films.

Perspective on the Interfacial Reduction Reaction

Chemical reactions involving oxidation and reduction processes at interfaces may vary from those in conventional liquid-phase or solid-phase reactions and could influence the overall outcome. This article primarily features a study on metal-ligand coordination at the solid-liquid interface. Of particular mention is the spontaneous reduction of Cu(II) to Cu(I) at a solid-liquid interface without the need of any extraneous reducing agent, unlike in the liquid-phase reaction whereby no reduction of Cu(II) to Cu(I) took place. As a consequence of the interfacial reduction reaction (IRR), thin films of Cu-TCNQ (tetracyanoquinodimethane) and Cu-HCF (hexacyanoferrate) were successfully deposited onto a thiol-functionalized Au substrate via a layer-by-layer (LbL) method. IRR is anticipated to be useful in generating new functional and stimuli-responsive materials, which are otherwise difficult to achieve via conventional liquid-phase reactions.

Metal-Organic Frameworks for Food Safety

Food safety is a prevalent concern around the world. As such, detection, removal, and control of risks and hazardous substances present from harvest to consumption will always be necessary. Metal-organic frameworks (MOFs), a class of functional materials, possess unique physical and chemical properties, demonstrating promise in food safety applications. In this review, the synthesis and porosity of MOFs are first introduced by some representative examples that pertain to the field of food safety. Following that, the application of MOFs and MOF-based materials in food safety monitoring, food processing, covering preservation, sanitation, and packaging is overviewed. Future perspectives, as well as potential opportunities and challenges faced by MOFs in this field will also be discussed. This review aims to promote the development and progress of MOF chemistry and application research in the field of food safety, potentially leading to novel solutions.