Structures of Metal-Organic Frameworks with Rod Secondary Building Units

A metal-organic framework with rod secondary building unit based on the Boerdijk-Coxeter helix

The renowned aperiodic Boerdijk-Coxeter helix is identified, with a modified, periodic form, in a MOF named ROD-1 [formulated as Cd(L), H₂L = (3,5-dimethyl-1H-(pyrazol-4-yl)-methylene)benzoic acid], which exhibits unusual gas adsorption behaviours attributed to guest-guest interactions, and also interesting structural dynamics responding to temperature variation and gas adsorption.

Insights into the Use of Metal-Organic Framework As High-Performance Anticorrosion Coatings

Metal-organic frameworks (MOFs) have shown great potential in gas storage and separation, energy storage and conversion, vapor sensing, and catalysis. Nevertheless, rare attention has been paid to their anticorrosion performances. At present, substantial hydrophobic and water stable MOFs (like ZIF-8), which are potentially favorable for their applications in anticorrosion industry, have been successfully designed and prepared. In this study, a facile ligand-assisted conversion strategy was employed to fully convert ZnAl-CO₃ layered double hydroxide (LDH) precursor buffer layers to well intergrown ZIF-8 coatings. DC Polarization tests indicated that prepared ZIF-8 coatings showed the corrosive current 4 orders of magnitude lower than that of bare Al substrates, demonstrating that MOF materials were superb candidates for high-performance anticorrosion coatings.

Highly Stable Copper(I)-Based Metal-Organic Framework Assembled with Resorcin[4]arene and Polyoxometalate for Efficient Heterogeneous Catalysis of Azide-Alkyne "Click" Reaction

A new highly stable copper(I)-based metal-organic framework (MOF), namely, [Cu^I₄(SiW₁₂O₄₀)(L)]·6H₂O·2DMF (1), was synthesized by incorporating Keggin-type polyoxometalate (POM) anions and a functionalized wheel-like resorcin[4]arene-based ligand (L) under sovothermal condition. 1 exhibits a charming 3D supramolecular architecture sandwiched by the POM anions. Noticeably, 1 has exceptional chemical stability, especially in organic solvents or aqueous solutions with a wide range of pH values. Considering the catalytically active Cu(I) sites in 1, the azide-alkyne cycloaddition (AAC) reaction was studied by employing 1 as the heterogeneous catalyst. Most strikingly, 1 exhibits excellent catalytic activity as well as recyclability for the AAC reaction.

A high-activity cobalt-based MOF catalyst for [2 + 2 + 2] cycloaddition of diynes and alkynes: insights into alkyne affinity and selectivity control

This work develops a highly efficient metal–organic framework (MOF) catalyst for the straightforward synthesis of functionalized benzenes via [2 + 2 + 2] cycloaddition. As efficient cooperative catalyst for such reactions, Co-MOF-1, shows great sustainability and efficiency. This new catalytic system can lead to the generation of a series of structurally diverse benzenes in good to excellent yields (up to 95%).

Heterogenous catalysis of [2 + 2 + 2] cycloaddition was firstly achieved by a low-cost, air-stable and reusable Co-MOF catalyst, affording structurally diverse functionalized benzenes under mild conditions with high efficiency and selectivity.

Precise Synthesis of Well-Defined Inorganic-Organic Hybrid Particles

Synthesis of hybrid particles toward precisely designed hierarchical nanoarchitectures is summarized. In order to satisfy the demands for a variety of materials' performances, the selection of materials, composition and synthesis is carefully done. Flow reactors are one of the useful synthetic means to prepare hybrid materials, especially those with hierarchically and precisely designed multi-components hybrid particles, owing to the efficient mixing and heat exchange in the reactor as well as its connectable (both parallel and sequential) feature. In this review article, after the summary of the preparation of hybrids based on oxides and organics through conventional batch reactors, the application of flow reactors to the preparation of various hybrid particles is introduced to highlight the present status and future possibility of the flow reactor synthesis.

Novel Prussian-blue-analogue microcuboid assemblies and their derived catalytic performance for effective reduction of 4-nitrophenol

Novel Co–Fe PBA microcuboids (MCBs) were solvothermally synthesized in the presence of PVP for the first time, and the cuboid-derived catalyst, CoFe/NC-MCBs, showed excellent catalytic performance for the reduction of 4-nitrophenol.

A novel polyhedron-based metal–organic framework with high performance for gas uptake and light hydrocarbon separation

A novel Zn-PMOF with high density of OMSs and LBSs was successfully assembled by the SBBs strategy and exhibited high performance for the capture and separation of CO₂ and C₃H₈ over CH₄.

A general and efficient approach for tuning the crystal morphology of classical MOFs

The size/morphology-controlled synthesis of classical MOFs with 2-methylimidazole (2-MI) as a coordination modulator.

Upgrading gasoline to high octane numbers using a zeolite-like metal–organic framework molecular sieve with ana-topology

We report the synthesis of the first zeolite-like metal–organic framework (ZMOF) with ana topology for the selective separation of linear, mono- and dibranched paraffins.

An efficient approach for enhancing the catalytic activity of Ni-MOF-74 via a relay catalyst system for the selective oxidation of benzylic C–H bonds under mild conditions

A facile and efficient approach for enhancing the catalytic activity of Ni-MOF-74 via a relay catalysis strategy with [bmim]Br was developed, which is excellent for the selective oxidation of benzylic C–H bond under mild conditions.

Operando study of palladium nanoparticles inside UiO-67 MOF for catalytic hydrogenation of hydrocarbons

Formation of Pd nanoparticles inside UiO-67 MOF was monitored by in situ X-ray absorption and diffraction.

Actinide-based MOFs: a middle ground in solution and solid-state structural motifs

In this review, we highlight how recent advances in the field of actinide structural chemistry of metal–organic frameworks (MOFs) could be utilized towards investigations relative to efficient nuclear waste administration, driven by the interest towards development of novel actinide-containing architectures as well as concerns regarding environmental pollution and nuclear waste storage.

Assembly of a series of zinc coordination polymers based on 5-functionalized isophthalic acids and dipyridyl

A series of zinc coordination polymers based on 5-functionalized isophthalate and flexible dipyridyl ligands have been prepared. Their thermal and luminescent properties in the solid state were also investigated.

A multifunctional microporous metal–organic framework: efficient adsorption of iodine and column-chromatographic dye separation

In this work, a multifunctional microporous metal–organic framework (MOF), [Cd(ABTC)(H₂O)₂(DMA)]·4DMA (JLNU-4; JLNU = Jilin Normal University; H₄ABTC = 3,3′,5,5′-azobenzenetetracarboxylic acid), has been synthesized based on the ligand H₄ABTC under solvothermal conditions. JLNU-4 shows excellent uptake of iodine both in solution and in the vapor phase, owing to the existence of a microporous structure in JLNU-4. The adsorption kinetics during the process of iodine adsorption were analyzed via a series of qualitative and quantitative analyses, such as the Langmuir and Freündlich adsorption isotherms. In addition, according to UV/vis spectroscopy analysis and the colour variance of JLNU-4, the relatively small sized dye methylene blue (MB) could be efficiently adsorbed by JLNU-4, through size-exclusion effects. Particularly, JLNU-4 can serve as a column-chromatographic filler for the separation of dye molecules. Therefore, JLNU-4 is a multifunctional microporous MOF for iodine adsorption and column-chromatographic dye separation.

JLNU-4 shows excellent uptake of iodine and could selectively adsorb dyes; therefore it can be used for column-chromatographic dye separation.

A water stable microporous metal–organic framework based on rod SBUs: synthesis, structure and adsorption properties

A microporous metal–organic framework based on rod SBUs with high water stability and good selectivity for CO₂ separation has been successfully synthesized.

A novel metal–organic framework based on hexanuclear Co(ii) clusters as an anode material for lithium-ion batteries

A new metal–organic framework, [Co(L)]·1.5H₂O (1), has been successfully synthesized, where its electrochemical application has been investigated.

A [Cr2Ni] coordination polymer: slow relaxation of magnetization in quasi-one-dimensional ferromagnetic chains

The first example of a Ni^II–Cr^III chain to exhibit slow relaxation of magnetization is reported.

Color tuning and white light emission by codoping in isostructural homochiral lanthanide metal–organic frameworks

Pure white-light emission and fluent light-emitting color change can be facilely obtained by codoping isostructural homochiral lanthanide metal–organic frameworks.

Trisiloxane-centred metal–organic frameworks and hydrogen bonded assemblies

A trisiloxane-centred hexacarboxylic acid linker has been synthesized and used in the preparation of new hybrid MOF materials.

Chiral metal–organic frameworks constructed from four-fold helical chain SBUs for enantioselective recognition of α-hydroxy/amino acids

Three chiral 3D metal–carboxylate frameworks have been successfully synthesized, featuring four-fold helical metal chains as SBUs. Co-MOFs could recognize enantio-selectively α-hydroxy/amino acids by the change of CD signals.

Luminescent metal–organic frameworks as chemical sensors: common pitfalls and proposed best practices

In this review we approach the emerging field of sensors based on luminescent metal–organic frameworks from the perspective of the most commonly encountered pitfalls and we suggest best practices so that they can be avoided.

New synthetic strategies to prepare metal–organic frameworks

This critical review summarizes the recent developments in the application of new synthetic strategies for preparing MOFs, including the ionothermal method, deep eutectic solvent usage, surfactant-thermal process, and mechanochemistry.

Resorcin[4]arene-Based Microporous Metal-Organic Framework as an Efficient Catalyst for CO2 Cycloaddition with Epoxides and Highly Selective Luminescent Sensing of Cr2O72

A stable microporous anionic metal-organic framework (MOF), [(CH₃)₂NH₂]₆[Cd₃L(H₂O)₂]·12H₂O (1), has been synthesized via solvothermal assembly of a new resorcin[4]arene-functionalized dodecacarboxylic acid (H₁₂L) and Cd(II) cations. The constructed MOF (1) was characterized by single-crystal X-ray diffraction and other physicochemical analyses. 1 exhibits a fascinating 3D microporous framework structure, in which the free water molecules and the [(CH₃)₂NH₂]⁺ cations were located. Remarkably, the exposed Lewis acid Cd(II) sites of activated 1 make it an efficient heterogeneous catalyst for the cycloaddition of CO₂ with epoxides at 1 and 20 atm. Importantly, the activated samples of 1 can be reused at least five circles with excellent catalytic performance. Moreover, the fluorescence detection of Cr₂O₇^2- and Fe³⁺ was studied by using 1 as a potential luminescent sensor.

Three-Dimensional Networked Metal-Organic Frameworks with Conductive Polypyrrole Tubes for Flexible Supercapacitors

Metal-organic frameworks (MOFs) with high porosity and a regular porous structure have emerged as a promising electrode material for supercapacitors, but their poor electrical conductivity limits their utilization efficiency and capacitive performance. To increase the overall electrical conductivity as well as the efficiency of MOF particles, three-dimensional networked MOFs are developed via using preprepared conductive polypyrrole (PPy) tubes as the support for in situ growth of MOF particles. As a result, the highly conductive PPy tubes that run through the MOF particles not only increase the electron transfer between MOF particles and maintain the high effective porosity of the MOFs but also endow the MOFs with flexibility. Promoted by such elaborately designed MOF-PPy networks, the specific capacitance of MOF particles has been increased from 99.2 F g^-1 for pristine zeolitic imidazolate framework (ZIF)-67 to 597.6 F g^-1 for ZIF-PPy networks, indicating the importance of the design of the ZIF-PPy continuous microstructure. Furthermore, a flexible supercapacitor device based on ZIF-PPy networks shows an outstanding areal capacitance of 225.8 mF cm^-2, which is far above other MOFs-based supercapacitors reported up to date, confirming the significance of in situ synthetic chemistry as well as the importance of hybrid materials on the nanoscale.

Straightforward Loading of Imidazole Molecules into Metal-Organic Framework for High Proton Conduction

A one-step straightforward strategy has been developed to incorporate free imidazole molecules into a highly stable metal-organic framework (NENU-3, ([Cu₁₂(BTC)₈(H₂O)₁₂][HPW₁₂O₄₀])·Guest). The resulting material Im@(NENU-3) exhibits a very high proton conductivity of 1.82 × 10^-2 S cm^-1 at 90% RH and 70 °C, which is significantly higher than 3.16 × 10^-4 S cm^-1 for Im-Cu@(NENU-3a) synthesized through a two-step approach with mainly terminal bound imidazole molecules inside pores. Single crystal structure reveals that imidazole molecules in Im-Cu@(NENU-3a) isolate lattice water molecules and then block proton transport pathway, whereas high concentration of free imidazole molecules within Im@(NENU-3) significantly facilitate successive proton-hopping pathways through formation of hydrogen bonded networks.

Cyclobutane-1,3-Diacid (CBDA): A Semi-Rigid Building Block Prepared by [2+2] Photocyclization for Polymeric Materials

A previously overlooked building block, cyclobutane-1,3-diacid (CBDA), is introduced to materials synthesis due to its great potentials. As an example of CBDA, α-truxillic acid or 2,4-diphenylcyclobutane-1,3-dicarboxylic acid, was readily synthesized from commercially available trans-cinnamic acid. This CBDA showed outstanding stability both in sunlight and upon heating. While its two carboxylic acid groups can be readily utilized in connecting with other molecules to form new materials, the cyclobutane ring was able to tolerate acid and base treatments showing good chemical stability. A series of cyclobutane-containing polymers (CBPs), namely poly-α-truxillates, were obtained by condensation between α-truxillic acid and diols including ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-petanediol, and 1,6-hexanediol. The structures of these poly-α-truxillates were analyzed by NMR, FT-IR, and HRMS. Powder X-ray diffraction results of the poly-α-truxillates indicated that they are semi-crystalline materials. Preliminary thermal, chemical, and photochemical tests showed that the poly-α-truxillates exhibited comparable stabilities to PET.

Flexible Zirconium MOF as the Crystalline Sponge for Coordinative Alignment of Dicarboxylates

Because of their permanent porosity and unparalleled structural diversities, flexible metal-organic frameworks (MOFs) are promising and highly desirable in host-guest chemistry. In this work, we employed a flexible Zr-MOF system, namely PCN-700 species, as the crystalline sponge for guest inclusion. A family of linear dicarboxylate ligands was adsorbed in the void space of PCN-700, which were subsequently confirmed by crystallographic observation. The stretching degree of the PCN-700 series was varied by means of dicarboxylate encapsulation through coordinative alignment.

Valuing Metal-Organic Frameworks for Postcombustion Carbon Capture: A Benchmark Study for Evaluating Physical Adsorbents

The development of practical solutions for the energy-efficient capture of carbon dioxide is of prime importance and continues to attract intensive research interest. Conceivably, the implementation of adsorption-based processes using different cycling modes, e.g., pressure-swing adsorption or temperature-swing adsorption, offers great prospects to address this challenge. Practically, the successful deployment of practical adsorption-based technologies depends on the development of made-to-order adsorbents expressing mutually two compulsory requisites: i) high selectivity/affinity for CO₂ and ii) excellent chemical stability in the presence of impurities. This study presents a new comprehensive experimental protocol apposite for assessing the prospects of a given physical adsorbent for carbon capture under flue gas stream conditions. The protocol permits: i) the baseline performance of commercial adsorbents such as zeolite 13X, activated carbon versus liquid amine scrubbing to be ascertained, and ii) a standardized evaluation of the best reported metal-organic framework (MOF) materials for carbon dioxide capture from flue gas to be undertaken. This extensive study corroborates the exceptional CO₂ capture performance of the recently isolated second-generation fluorinated MOF material, NbOFFIVE-1-Ni, concomitant with an impressive chemical stability and a low energy for regeneration. Essentially, the NbOFFIVE-1-Ni adsorbent presents the best compromise by satisfying all the required metrics for efficient CO₂ scrubbing.