A Stable Metal-Organic Framework Featuring a Local Buffer Environment for Carbon Dioxide Fixation

Progress of MOF-Derived Functional Materials Toward Industrialization in Solar Cells and Metal-Air Batteries

The cutting-edge photovoltaic cells are an indispensable part of the ongoing progress of earth-friendly plans for daily life energy consumption. However, the continuous electrical demand that extends to the nighttime requires a prior deployment of efficient real-time storage systems. In this regard, metal-air batteries have presented themselves as the most suitable candidates for solar energy storage, combining extra lightweight with higher power outputs and promises of longer life cycles. Scientific research over non-precious functional catalysts has always been the milestone and still contributing significantly to exploring new advanced materials and moderating the cost of both complementary technologies. Metal-organic frameworks (MOFs)-derived functional materials have found their way to the application as storage and conversion materials, owing to their structural variety, porous advantages, as well as the tunability and high reactivity. In this review, we provide a detailed overview of the latest progress of MOF-based materials operating in metal-air batteries and photovoltaic cells.

Rational design and synthesis of a stable pillar-layer NaI-organic framework as a multi-responsive luminescent sensor in aqueous solutions

A stable pillar-layer Na^I-organic framework, [Na₂(DCPB)∙(H₂O)₂]_n (namely 1), was rationally designed and synthesized by the assemble process of Na^I and 1,3-di(4'-carboxyl-phenyl)benzene (H₂DCPB). Benefiting from the luminescent property and high stability in water, the as-synthesized 1 is a potential multi-responsive luminescent sensor material toward Cr₂O₇^2-, Fe³⁺, and nitrofurazone (NFZ) in water. Ground 1 not only has the excellent detectability and selectivity but also possesses outstanding stability and circularity. The calculated K_sv values of 1 are 8.8×10³ for Fe³⁺, 9.9×10³ for Cr₂O₇^2-, and 2.7×10⁴ M^-1 for NFZ in aqueous solutions, respectively. Furthermore, 1 is able to accurately detect NFZ in real bovine serum samples through luminescence detection technology.

Spatially Ordered Arrangement of Multifunctional Sites at Molecule Level in a Single Catalyst for Tandem Synthesis of Cyclic Carbonates

With fossil energy resources increasingly drying up and gradually causing serious environmental impacts, pursuing a tandem and green synthetic route for a complex and high-value-added compound by using low-cost raw materials has attracted considerable attention. In this regard, the selective and efficient conversion of light olefins with CO₂ into high-value-added organic cyclic carbonates (OCCs) is of great significance owing to their high atom economy and absence of the isolation of intermediates. To fulfill this expectation, a multifunctional catalytic system with controllable spatial arrangement of varied catalytic sites and stable texture, in particular, within a single catalyst, is generally needed. Here, by using a stepwise electrostatic interaction strategy, imidazolium-based ILs and Au nanoparticles (NPs) were stepwise immobilized into a sulfonic group grafted MOF to construct a multifunctional single catalyst with a highly ordered arrangement of catalytic sites. The Au NPs and imidazolium cation are separately responsible for the selective epoxidation and cycloaddition reaction. The mesoporous cage within the MOF enriches the substrate molecules and provides a confined catalytic room for the tandem catalysis. More importantly, the highly ordered arrangement of the varied active sites and strong electrostatic attraction interaction result in the intimate contact and effective mass transfer between the catalytic sites, which allow for the highly efficient (>74% yield) and stable (repeatedly usage for at least 8 times) catalytic transformation. The stepwise electrostatic interaction strategy herein provides an absolutely new approach in fabricating the controllable multifunctional catalysts, especially for tandem catalysis.

Metal-Organic Frameworks of Cu(II) Constructed from Functionalized Ligands for High Capacity H2 and CO2 Gas Adsorption and Catalytic Studies

Two Cu(II)-based metal-organic frameworks (MOFs) having paddle-wheel secondary building units (SBUs), namely, 1_Me and 1_ipr, were synthesized solvothermally using two new bent di-isophthalate ligands incorporating different substituents. The MOFs showed high porosity (BET surface area, 2191 m²/g for 1_Me and 1402 m²/g for 1_ipr). For 1_Me, very high CO₂ adsorption (98.5 wt % at 195 K, 42.9 wt % at 273 K, 23.3 wt % at 298 K) at 1 bar was found, while for 1_ipr, it was significantly less (14.3 wt % at 298 K and 1 bar, 54.4 wt % at 298 K at 50 bar). 1_Me exhibited H₂ uptake of 3.2 wt % at 77 K and 1 bar of pressure, which compares well with other benchmark MOFs. For 1_ipr, the H₂ uptake was found to be 2.54 wt % under similar experimental conditions. The significant adsorption of H₂ and CO₂ for 1_Me could be due to the presence of micropores as well as unsaturated metal sites in these MOFs besides the presence of substituents that interact with the gas molecules. The experimental adsorption behavior of the MOFs could be justified by theoretical calculations. Additionally, catalytic conversions of CO₂ and CS₂ into useful chemicals like cyclic carbonates, cyclic trithiocarbonates, and cyclic dithiocarbonates could be achieved.

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.

Epitaxial Growth of Highly Transparent Metal-Porphyrin Framework Thin Films for Efficient Bifacial Dye-Sensitized Solar Cells

Bifacial dye-sensitized solar cells (DSSCs) are regarded as promising solar energy conversion devices with high efficiency and less resource consumption. In this work, a highly transparent and efficient counter electrode (CE) is fabricated by introducing highly dispersed single Pt atoms doped into the van der Waals layer-by-layer epitaxially grown Zn-TCPP thin film (Zn-TCPP-Pt). The resulting Zn-TCPP-Pt CE has similar catalytic activity to commercial Pt CE but shows a better light transmission capacity in the range of visible light. The bifacial DSSC with Zn-TCPP-Pt thin film CE achieves high power conversion efficiencies of 5.48 and 4.88% under front-side and rear-side irradiation, respectively. With maximized atomic efficiency, excellent performance was obtained with about 1% Pt content and highly transparent CEs. Therefore, the light energy resource utilization rate of such less Pt and transparence CE is greatly improved in bifacial dye-sensitized solar cells, making it a promising candidate to replace Pt CE.

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.

Open metal site (OMS) and Lewis basic site (LBS)-functionalized copper–organic framework with high CO2 uptake performance and highly selective CO2/N2 and CO2/CH4 separation

A robust porous metal–organic framework with dual functionalities of open metal sites (OMSs) and O-rich Lewis basic sites (LBSs) has been designed and synthesized, and shows high CO₂ uptake and excellent selectivity for CO₂ over N₂ and CH₄.

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.

Rational Construction of a 2D PbII Coordination Polymer as a Sensitive Turn-Off Fluorescent Switch for Fe3+, Cr2O72−, and NFT

A PbII coordination polymer, [Pb(L)2]n (denoted as complex 1), was generated successfully by the assembly process of PbII and 5-fluoronicotinic acid (HL) under solvothermal synthesis. The obtained 1 was characterised by element analysis, powder and single-crystal X-ray diffraction, thermogravimetric analysis, and UV-vis and fluorescent spectroscopy. The resultant 1 has an outstanding application as a fluorescent sensor for Fe3+, Cr2O72−, and NFT with excellent selectivity and reusability.

State of the art methods and challenges of luminescent metal–organic frameworks for antibiotic detection

This review focuses on recent developments in the design and synthesis of luminescence MOFs for monitoring antibiotics.

A historical overview of the activation and porosity of metal–organic frameworks

A historical overview of the activation and porosity of MOFs including strategies to design and preserve permanent porosity in MOFs.

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.

Formation of CX Bonds in CO2 Chemical Fixation Catalyzed by Metal-Organic Frameworks

Transformation of CO₂ based on metal-organic framework (MOF) catalysts is becoming a hot research topic, not only because it will help to reduce greenhouse gas emission, but also because it will allow for the production of valuable chemicals. In addition, a large number of impressive products have been synthesized by utilizing CO₂ . In fact, it is the formation of new covalent bonds between CO₂ and substrate molecules that successfully result in CO₂ solidly inserting into the products, and only four types of new CX bonds, including CH, CC, CN, and CO bonds, are observed in this exploration. An overview of recent progress in constructing CX bonds for CO₂ conversion catalyzed by various MOF catalysts is provided. The catalytic mechanism of generating different CX bonds is further discussed according to both structural features of MOFs and the interactions among CO₂ , substrates, as well as MOFs. The future opportunities and challenges in this field are also tentatively covered.

Highly Stable Copper(I)-Thiacalix[4]arene-Based Frameworks for Highly Efficient Catalysis of Click Reactions in Water

Environmentally friendly metal-organic frameworks (MOFs) have gained considerable attention for their potential use as heterogeneous catalysts. Herein, two Cu^I -based MOFs, namely, [Cu₄ Cl₄ L]⋅CH₃ OH⋅1.5 H₂ O (1-Cl) and [Cu₄ Br₄ L]⋅DMF⋅0.5 H₂ O (1-Br), were assembled with new functionalized thiacalix[4]arenes (L) and halogen anions X^- (X=Cl and Br) under solvothermal conditions. Remarkably, catalysts 1-Cl and 1-Br exhibit great stability in aqueous solutions over a wide pH range. Significantly, MOFs 1-Cl and 1-Br, as recycled heterogeneous catalysts, are capable of highly efficient catalysis for click reactions in water. The MOF structures, especially the exposed active Cu^I sites and 1D channels, play a key role in the improved catalytic activities. In particular, their catalytic activities in water are greatly superior to those in organic solvents or even in mixed solvents. This work proposes an attractive route for the design and self-assembly of environmentally friendly MOFs with high catalytic activity and reusability in water.

Atomic- and Molecular-Level Design of Functional Metal-Organic Frameworks (MOFs) and Derivatives for Energy and Environmental Applications

Continuing population growth and accelerated fossil-fuel consumption with recent technological advancements have engendered energy and environmental concerns, urging researchers to develop advanced functional materials to overcome the associated problems. Metal-organic frameworks (MOFs) have emerged as frontier materials due to their unique porous organic-inorganic hybrid periodic assembly and exceptional diversity in structural properties and chemical functionalities. In particular, the modular nature and modularity-dependent activity of MOFs and MOF derivatives have accentuated the delicate atomic- and molecular design and synthesis of MOFs, and their meticulous conversion into carbons and transition-metal-based materials. Synthetic control over framework architecture, content, and reactivity has led to unprecedented merits relevant to various energy and environmental applications. Herein, an overview of the atomic- and molecular-design strategies of MOFs to realize application-targeted properties is provided. Recent progress on the development of MOFs and MOF derivatives based on these strategies, along with their performance, is summarized with a special emphasis on design-structure and functionality-activity relationships. Next, the respective energy- and environmental-related applications of catalysis and energy storage, as well as gas storage-separation and water harvesting with close association to the energy-water-environment nexus are highlighted. Last, perspectives on current challenges and recommendations for further development of MOF-based materials are also discussed.

Multifunctional Polymolybdate-Based Metal-Organic Framework as an Efficient Catalyst for the CO2 Cycloaddition and as the Anode of a Lithium-Ion Battery

A three-dimensional polymolybdate-based metal-organic framework (POMOF) consisting of Zn-ε-Keggin unit and organic linker, {[PMo₈^VMo₄^VIO₃₇(OH)₃Zn₄][BPE]₂}·[BPE] (1), was successfully obtained by the hydrothermal method. Compound 1 is composed of Zn-ε-Keggin units and BPE ligands, featuring a fascinating 5-fold interpenetrating framework with dia topology. The catalytic performance of compound 1 was investigated, and experiments showed that 1 could effectively facilitate the cycloaddition reaction of CO₂ with epoxides as Lewis acid heterogeneous catalyst. Moreover, compound 1 also was studied as LIBs anode material, and it showed reversible capacity of 546 mA h g^-1 at 100th cycle.

UiO-type metal-organic frameworks with NHC or metal-NHC functionalities for N-methylation using CO2 as the carbon source

We demonstrate the first metal-organic framework (MOF) that catalyzes N-methylation of amines using 1 atm CO2 and phenylsilane under ambient conditions. Compared with its homogeneous analog, the incorporation of N-heterocyclic carbene (NHC) into the MOF provides more efficient catalysis with improved reaction kinetics, turnover numbers and recyclability. Moreover, the metalated NHC functionalized MOF achieves direct N-methylation of amines bearing carboxylate moieties, which are common building blocks in pharmaceutical chemistry.

Improving MOF stability: approaches and applications

This review summarizes recent advances in the design and synthesis of stable MOFs and highlights the relationships between the stability and functional applications.

Metal–organic frameworks (MOFs) have been recognized as one of the most important classes of porous materials due to their unique attributes and chemical versatility. Unfortunately, some MOFs suffer from the drawback of relatively poor stability, which would limit their practical applications. In the recent past, great efforts have been invested in developing strategies to improve the stability of MOFs. In general, stable MOFs possess potential toward a broader range of applications. In this review, we summarize recent advances in the design and synthesis of stable MOFs and MOF-based materials via de novo synthesis and/or post-synthetic structural processing. Also, the relationships between the stability and functional applications of MOFs are highlighted, and finally, the subsisting challenges and the directions that future research in this field may take have been indicated.

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.