A Versatile Microporous Zinc(II) Metal–Organic Framework for Selective Gas Adsorption, Cooperative Catalysis, and Luminescent Sensing

Porous MOF Featuring 2D Intersecting Channels Based on a Pentanuclear Mn5(COO)10CO3 Cluster with Upgrading of Pipeline Natural Gas

Natural gas plays a crucial role in daily and industrial production, but the impurities contained in natural gas limit its further use. It is very important to develop adsorbents that can separate CH4 from multicomponent mixtures, but there are still many challenges and problems. Herein, a novel porous MOF {[Mn5(pbdia)2(CO3)(H2O)2] ↔ 5H2O ↔ 2DMF}n (pbdia = 2,2'-(5-carboxy-1,3-phenylene)bis(oxy) diterephthalic acid) was successfully synthesized based on a flexible pentacarboxylic acid ligand and a unique pentanuclear Mn5(COO)10CO3 cluster. The MOF reveals a 3D porous structure with 2D intersecting channels, which shows high C3H8, C2H6, and CO2 adsorption capacities and affinities over CH4. Moreover, the ideal adsorption solution theory selectivities of C3H8/CH4, C2H6/CH4, and CO2/CH4 can reach 263.0, 27.0, and 7.7, respectively, suggesting a potential for removing the low content of C3H8, C2H6, and CO2 from pipeline natural gas, which was further confirmed by breakthrough curves and GCMC simulations.

Construction of a 3D Metal-Organic Framework and Its Composite for Water Remediation via Selective Adsorption and Photocatalytic Degradation of Hazardous Dye

In this work, a new bimetallic Na(I)-Zn(II) metal-organic framework (MOF), formulated as [Na₂Zn₃(btc)₂(μ-HCOO)₂(μ-H₂O)₈] _n (1) (H₃btc = benzene tricarboxylic acid), and its composite (ZnO@1) have been successfully synthesized using solvothermal and mechanochemical solid grinding methods. 1 and ZnO@1 were characterized by diffraction [single-crystal X-ray diffraction (XRD) and powder XRD], spectroscopic (ultraviolet-visible diffuse reflectance spectroscopy and Fourier transform infrared spectroscopy), microscopic (transmission electron microscopy), and thermal (thermogravimetric analysis) methods. The surface area and porosity of 1 were determined using a Brunauer-Emmett-Teller analyzer. Single-crystal diffraction of 1 confirms that Na1 and Zn2 have octahedral coordination environments, whereas Zn1 has a tetrahedral coordination geometry. Topological simplification of 1 shows a 3,6-connected kgd net. Na(I)-Zn(II) MOF (1) is crystallized with slight porosity and exhibits good tendency toward the encapsulation of zinc oxide nanoparticles (ZnO NPs). The photocatalytic behaviors of 1 and its composite (ZnO@1) were investigated over MB dye under sunlight illumination with promising degradation efficiencies of 93.69% for 1 and 97.53% for ZnO@1 in 80 min.

A Dihydrotetrazine-Functionalized Metal-Organic Framework as a Highly Selective Luminescent Host-Guest Sensor for Detection of 2,4,6-Trinitrophenol

Pore decoration of metal-organic frameworks (MOFs) with functional groups is a useful strategy to attain high selectivity toward specific analytes, especially in the presence of interfering molecules with similar structures and energy levels, through selective host-guest interactions. In this work, we applied a dihydrotetrazine-decorated MOF, TMU-34, with the formula [Zn(OBA)(H₂DPT)_0.5]_n·DMF, where H₂OBA is 4,4'-oxybis(benzoic acid) and H₂DPT is 3,6-bis(pyridin-4-yl)-1,4-dihydro-1,2,4,5-tetrazine, for the highly selective detection of phenolic NACs, especially TNP (94% quenching efficiency, detection limit 8.1 × 10^-6 M, K_SV = 182663 mol L^-1), in the presence of other substituted NACs especially -NH₂-substituted NACs. Investigations reveal that the quenching mechanism is dominated by photoinduced MOF-to-TNP electron transfer through possible hydrogen-bonding interactions between the phenolic hydroxyl group of TNP and dihydrotetrazine functions of TMU-34. Despite extensive publications on the detection of TNP in the presence of other NACs, the significance of this work will be elucidated if attention is paid to the fact that TMU-34 is among the rare and highly selective MOF-based TNP sensors in the presence of -NH₂-substituted NACs as the serious interferers.

Wireless Volatile Organic Compound Detection for Restricted Internet of Things Environments Based on Cataluminescence Sensors

Cataluminescence-based sensors do not require external light sources and complex circuitry, which enables them to avoid light scattering with high sensitivity, selectivity, and widely linear range. In this study, a wireless sensor system based on hierarchical CuO microspheres assembled from nano-sheets was constructed for Volatile Organic Compound (VOC) online detection. Through sensor characteristics and data process analysis, the results showed that the luminous sensor system has good luminous characteristics, including the intensity of visible light, high signal/noise (S/N) values, and very short response and recovery times. Different VOC concentration values can be detected on multiple wavelength channels and different Cataluminescence signal spectra separations can process multiple sets of Cataluminescence data combinations concurrently. This study also briefly studied the mechanism action of the Cataluminescence sensor, which can specifically be used for VOC detecting.

Current and future perspectives on catalytic-based integrated carbon capture and utilization

There exist several well-known methods with varying maturity for capturing carbon dioxide from emission sources of different concentrations, including absorption, adsorption, cryogenics and membrane separation, among others. The capture and separation steps can produce almost pure CO₂, but at substantial cost for being conditioned for transport and final utilization, with high economical risks to be considered. A possible way for the elimination of this conditioning and cost is direct CO₂ utilization, whether on-site in a further process but within the same plant, or in-situ, coupling both capture and conversion in the same unit. This approach is usually called integrated carbon capture and utilization (ICCU) or integrated carbon capture and conversion (ICCC), and has lately started receiving considerable attention in many circles. As CO₂ is already industrially employed in other sectors, such as food preservation, water treatment and conversion to high added-value chemicals and fuels such as methanol, methane, etc., among others, it is of great interest to explore the global ICCC approach. Catalytic-based processes play a key role in CO₂ conversion, and different technologies are gaining great attention from both academia and industry. However, the 'big picture of ICCU' and in which technology the efforts should focus on at large scale is still unclear. This review analyzes some promising concepts of ICCU specifically on CO₂ catalytic conversion, highlighting their current commercial relevance as well as challenges that have to be faced today and in the next future.

Applications of MOFs as Luminescent Sensors for Environmental Pollutants

The environmental pollution has become a serious issue because the pollutants can cause permanent damage to the DNA, nervous system, and circulating system, resulting in various incurable diseases, such as organ failure, malformation, angiocardiopathy, and cancer. The effective detection of environmental pollutants is urgently needed to keep them far away from daily life. Among the reported pollutant sensors, luminescent metal-organic frameworks (LMOFs) with tunable structures have attracted remarkable attention to detect the pollutants because of their excellent selectivity, sensitivity, and recyclability. Although lots of metal-organic framework (MOF)-based luminescent sensors have been summarized and discussed in previous reviews, the detection of environmental pollutants, especially radioactive ions and heavy metal ions, still have not been systematically presented. Here, the sensing mechanisms and construction principles of luminescent MOFs are discussed, and the state-of-the-art MOF-based luminescent sensors of environmental pollutants, including pesticides, antibiotics, explosives, VOCs, toxic gas, toxic small molecules, radioactive ions, and heavy metal ions are highlighted. This comprehensive review may further guide the development of luminescent MOFs and promote their practical applications for sensing environmental pollutants.

General synthesis of hierarchical sheet/plate-like M-BDC (M = Cu, Mn, Ni, and Zr) metal-organic frameworks for electrochemical non-enzymatic glucose sensing

Two-dimensional metal-organic frameworks (2D MOFs) are an attractive platform to develop new kinds of catalysts because of their structural tunability and large specific surface area that exposes numerous active sites. In this work, we report a general method to synthesize benzene dicarboxylic acid (BDC)-based MOFs with hierarchical 3D morphologies composed of 2D nanosheets or nanoplates. In our proposed strategy, acetonitrile helps solvate the metal ions in solution and affects the morphology, while polyvinylpyrrolidone (PVP) serves as a shape-control agent to assist in the nucleation and growth of MOF nanosheets. PVP also acts as a depletion agent to drive the assembly of the hierarchical sheet/plate-like M-BDC under solvothermal conditions. Further, we also demonstrate the flexibility of the proposed method using numerous coordinating metal ions (M = Cu, Mn, Ni, and Zr). The potential of these MOFs for electrochemical glucose sensing is examined using the hierarchical sheet-like Ni-BDC MOF as the optimum sample. It drives the electrocatalytic oxidation of glucose over a wide range (0.01 mM to 0.8 mM) with high sensitivity (635.9 μA mM-1 cm-2) in the absence of modification with carbon or the use of conductive substrates. It also demonstrates good selectivity with low limit of detection (LoD = 6.68 μM; signal/noise = 3), and fast response time (<5 s).

Triggering Lewis Acidic Nature through the Variation of Coordination Environment of Cd-Centers in 2D-Coordination Polymers

The rational design and successful synthesis of novel functional metal-organic frameworks relies on careful selection of metals and versatile organic ligands. A newly designed pyrazole-based dicarboxylate ligand, 5-(3,5-dimethyl-1H-pyrazol-1-yl) 1,3-benzenedicarboxylic acid (H₂L), was utilized to obtain two new Cd-based coordination polymers I [Cd(L)(H₂O)]·H₂O and II [Cd(L)] under similar reaction conditions via solvothermal strategy. Single-crystal X-ray data confirmed that compound I exhibits a two-dimensional (2D) skeleton comprising pentagonal bipyramidal Cd-ions and an organic ligand moiety. Compound II has also formed a two-dimensional layer arrangement with the connectivity between trigonal bipyramidal Cd-ions and the organic ligand. Topological analysis revealed that compound I has formed unique 4³.6³ net topology while compound II has displayed a 4⁴.6² sql net topology with 2D frameworks. The Lewis acidic nature of both I and II containing a Cd²⁺ metal center has been correlated with the coordination number through dye adsorption-desorption and catalysis studies. The selective adsorption of anionic dye and the extent of adsorption are interrelated with the Cd-ion geometry. For the first time, the role of coordinated water molecule has been analyzed through heterogeneous catalysis reaction (i.e., cyanosilylation) with Cd-based 2D-coordination polymers (CPs). The plausible mechanisms have been proposed to explain the subsequent role of coordination number and environment in CPs.

Design and Construction of a Metal-Organic Framework as an Efficient Luminescent Sensor for Detecting Antibiotics

We first design and synthesize a dendritic aromatic 6-carboxyl linker (H₆TDCPB), which is successfully assembled with Cd(II) ion to construct a porous metal-organic framework with a raw Cd₆ cluster, {[Cd₃(TDCPB)·2DMAc]·DMAc·4H₂O}_n (namely, complex 1). More interestingly, six adjacent linkers are packed together by π-π-stacking interactions to form an amazing six-molecule accumulation in the crystal structure. By virtue of high stability and luminescent properties, the as-synthesized sample not merely owns an excellent detectable ability but also possesses an outstanding selectivity for nitrofurans with remarkable recursitivity.

The synthesis of metal-organic frameworks with template strategies

The synthesis of metal-organic frameworks (MOFs) with a template strategy is still fascinating and has received considerable attention from structural chemists. In this review, developments in tuning MOF hosts or pore structures with a template strategy in the past decades are summarized. By adding templates into MOF precursors, novel template@MOF materials can always be obtained, which cannot be accessed by traditional synthesis procedures. Template@MOF materials can be structurally characterized to help understand the interactions between host frameworks and guest templates. On the other hand, changing the species or amount of template may lead to a pore structure change that can be used as a molecular container to load functional guest molecules with matching sizes for specific applications. It is hoped that this review will provide future researchers with new insight into the design and synthesis of MOF materials by applying suitable templates.

Two novel lead-based coordination polymers for luminescence sensing of anions, cations and small organic molecules

A novel lead-based compound is reported as a multi-responsive luminescent sensor for detecting anions, cations and small organic molecules, especially Cr₂O₇²⁻, CrO₄²⁻, Fe³⁺ and nitrobenzene.

Constructing an Interpenetrated NiII-Based Coordination Polymer Based on a Flexible Dicarboxylate Ligand and an N-Donor Ligand: Preparation, Topological Diversity, and Catalytic Properties

A novel coordination polymer (CP) was constructed using 1,3-bis(4-carboxyphenoxy) propane (H2bcp), 1,4-bis(1-imidazol-yl)-2,5-dimethyl benzene (bimb), and NiII ions. [Ni(bcp)(bimb)]·H2O]n (1) shows an interesting 2D+2D → 3D inclined polyrotaxane topology. The structure was characterised by many methods. This work indicates that the flexible and neutral pyridine ligand plays a significant role in constructing CPs. Furthermore, 1 is a highly efficient catalyst for the reaction of CO2 and epoxides.

Coordinatively unsaturated metal sites (open metal sites) in metal–organic frameworks: design and applications

The defined synthesis of OMS in MOFs is the basis for targeted functionalization through grafting, the coordination of weakly binding species and increased (supramolecular) interactions with guest molecules.

Metal–organic frameworks for the energy-related conversion of CO2 into cyclic carbonates

MOFs are promising heterogeneous catalysts for chemical fixation of CO₂ and epoxides into cyclic carbonates.

Sensing organic analytes by metal–organic frameworks: a new way of considering the topic

In this review, our goal is comparison of advantageous and disadvantageous of MOFs about signal-transduction in different instrumental methods for detection of different categories of organic analytes.

A stimuli responsive multifunctional ZMOF based on an unorthodox polytopic ligand: reversible thermochromism and anion triggered metallogelation

A novel Cd(ii)-ZMOF with a unique sodalite topology has been successfully designed and synthesized using a flexible polytopic compartmental ligand. The microporous complex contains 1D hexagonal channels with large void space for the accommodation of guest molecules. This work demonstrates a new paradigm for designing and functionalizing zeolite-type frameworks. The triconnected linker forms coordination polymer gels in the presence of Cd2+ and the gelation was controlled by the presence of specific anions. They possess good thermal stability and exhibit thixotropic behavior. Optical properties revealed that the complex is exclusively thermochromic and undergoes a reversible transition at 80 °C, changing its color from yellow to orange red. Owing to the large voids in the framework, the complex can serve as a host for use in dye adsorption. Thus this paper offers a new MOF material with exceptional chromic behavior, gelation properties and adsorption capability for the development of high performance multifunctional materials.

A Water-Stable Terbium(III)-Organic Framework as a Chemosensor for Inorganic Ions, Nitro-Containing Compounds and Antibiotics in Aqueous Solutions

Effective detection of organic/inorganic pollutants, such as antibiotics, nitro-compounds, excessive Fe³⁺ and MnO₄ ^- , is crucial for human health and environmental protection. Here, a new terbium(III)-organic framework, namely [Tb(TATAB)(H₂ O)]⋅2H₂ O (Tb-MOF, H₃ TATAB=4,4',4''-s-triazine-1,3,5-triyltri-m-aminobenzoic acid), was assembled and characterized. The Tb-MOF exhibits a water-stable 3D bnn framework. Due to the existence of competitive absorption, Tb-MOF has a high selectivity for detecting Fe³⁺ , MnO₄ ^- , 4-nirophenol and nitroimidazole (ronidazole, metronidazole, dimetridazole, ornidazole) in aqueous through luminescent quenching. The results suggest that Tb-MOF is a simple and reliable reagent with multiple sensor responses in practical applications. To the best of our knowledge, this work represents the first Tb^III -based MOF as an efficient fluorescent sensor for detecting metal ions, inorganic anions, nitro-compounds, and antibiotics simultaneously.

A 4'-(4-carboxyphenyl)-3,2':6',3''-terpyridine-based luminescent cadmium(II) coordination polymer for the detection of 2,4,6-trinitrophenol

The title coordination polymer, poly[bis[μ3-4-(3,2':6',3''-terpyridin-4'-yl)benzoato]cadmium(II)], [Cd(C₂₂H₁₄N₃O₂)₂]_n or [Cd(3-cptpy)₂]_n, (I), has been synthesized solvothermally and characterized by IR spectroscopy, thermogravimetric analysis, and single-crystal and powder X-ray diffraction. The structure is composed of 3-cptpy^- ligands bridging Cd atoms, with each Cd atom coordinated by six ligands and each ligand coordinating to three Cd atoms. Each Cd atom is in a slightly distorted trans-N₂O₄ octahedral environment, forming a two-dimensional layer structure with a (3,6)-connected topology. Layers are linked to each other by π-π stacking, resulting in a three-dimensional supramolecular framework. The strong luminescence and good thermal stability of (I) indicate that it can potentially be used as a luminescence sensor. The compound also shows a highly selective and sensitive response to 2,4,6-trinitrophenol through the luminescence quenching effect.

Crystal structure of diaqua-dichlorido-bis(μ3-6,6′-(hydrazine-1,2-diylidenebis(methanylylidene))bis(2-methoxyphenolato)κ6 O,N:N′,O′,O′:O′′)trizinc(II) - ethanol (1/2), C36H44Cl2N4O12Zn3

C36H44Cl2N4O12Zn3, orthorhombic, Pbca (no. 61), a = 8.3378(8) Å, b = 21.188(2) Å, c = 22.802(2) Å, Z = 4, V = 4028.3(7) Å3, R gt(F) = 0.0513, wR ref(F 2) = 0.1193, T = 296(2) K.