Fabrication Methods of Continuous Pure Metal-Organic Framework Membranes and Films: A Review.

Metal-organic frameworks (MOFs) have drawn intensive attention as a class of highly porous, crystalline materials with significant potential in various applications due to their tunable porosity, large internal surface areas, and high crystallinity. This paper comprehensively reviews the fabrication methods of pure MOF membranes and films, including in situ solvothermal synthesis, secondary growth, electrochemical deposition, counter diffusion growth, liquid phase epitaxy and solvent-free synthesis in the category of different MOF families with specific metal species, including Zn-based, Cu-based, Zr-based, Al-based, Ni-based, and Ti-based MOFs.

One-Step Synthesis of Al-Doped UiO-66 Nanoparticle for Enhanced Removal of Organic Dyes from Wastewater.

In this study, a series of Al-doped metal-organic frameworks (AlZr-UiO-66) were synthesized through a one-step solvothermal method. Various characterization techniques, including X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and N sorption measurement, suggested that the Al doping was uniform and barely influenced the crystallinity, chemical stability, and thermal stability of the materials. Two cationic dyes, safranine T (ST) and methylene blue (MB), were selected for investigating the adsorption performances of Al-doped UiO-66 materials.

Highly efficient lithium adsorption and stable isotope separation by metal-organic frameworks.

The effects of a series of MOFs on the adsorption and separation of lithium isotopes were investigated in this paper. Seven kinds of MOF were prepared, and the characterization studies of MIL-100(Fe) before and after adsorption by X-ray photoelectron spectroscopy (XPS) demonstrated the potential chemical interaction between Fe and Li. The influence of metal ions, counter-ions and solvents on the adsorption capacity and separation factor was investigated.

Novel Fluorine-Pillared Metal-Organic Framework for Highly Effective Lithium Enrichment from Brine.

The continuously developing lithium battery market makes seeking a reliable lithium supply a top priority for technology companies. Although metal-organic frameworks have been extensively researched as adsorbents owing to their exceptional properties, lithium adsorption has been scarcely investigated. Herein, we prepared a novel cuboid rod-shaped three-dimensional framework termed composed of fluorine-pillared coordination layers of Fe-O inorganic chains and benzene-1,3,5-tricarboxylate (BTC) linkages.

Structural Diversity of Zirconium Metal-Organic Frameworks and Effect on Adsorption of Toxic Chemicals.

While linkers with various conformations pose challenges in the design and prediction of metal-organic framework (MOF) structures, they ultimately provide great opportunities for the discovery of novel structures thereby enriching structural diversity. Tetratopic carboxylate linkers, for example, have been widely used in the formation of Zr-based MOFs due to the ability to target diverse topologies, providing a promising platform to explore their mechanisms of formation. However, it remains a challenge to control the resulting structures when considering the complex assembly of linkers with unpredicted conformations and diverse Zr node connectivities.

Node-Accessible Zirconium MOFs.

High-stability, zirconium-based metal-organic frameworks are attractive as heterogeneous catalysts and as model supports for uniform arrays of subsequently constructed heterogeneous catalysts-for example, MOF-node-grafted metal-oxy and metal-sulfur clusters. For hexa-Zr(IV)-MOFs characterized by nodes that are less than 12-connected, sites not used for linkers are ideally occupied by reactive and displaceable OH/HO pairs. The desired pairs are ideal for grafting the aforementioned catalytic clusters, while aqua-ligand lability renders them effective for exposing highly Lewis-acidic Zr(IV) sites (catalytic sites) to candidate reactants.

Fabrication of a sandwiched silicalite-1 membrane in a 2D confined space for enhanced alcohol/water separation.

A dense zeolite layer with a thickness of approximately 500 nm was demonstrated by a confined-space strategy in a sandwiched mode of (SiO2)/(silicalite-1)/(SiO2). The gel-free secondary growth methodology bypasses the post-calcination step, avoiding excess energy consumption and possible film damage. Significantly enhanced pervaporation separation was observed with separation factors of 136 and 113, and fluxes of 2.

Phase Transitions in Metal-Organic Frameworks Directly Monitored through In Situ Variable Temperature Liquid-Cell Transmission Electron Microscopy and In Situ X-ray Diffraction.

Zr-based metal-organic frameworks (MOFs) with tetratopic organic linkers have been extensively investigated owing to their versatile structural tunability. While diverse topologies and polymorphism in the resulting MOFs are often encountered with tetratopic linkers and Zr nodes, reports on phase transitions within these systems are rare. Thus, we have a limited understanding of polymorph transformations, hindering the rational development of pure phase materials.

Modular Synthesis of Highly Porous Zr-MOFs Assembled from Simple Building Blocks for Oxygen Storage.

The last decade has witnessed significant advances in the scale-up synthesis of metal-organic frameworks (MOFs) using commercially available and affordable organic linkers. However, the synthesis of MOFs using elongated and/or multitopic linkers to access MOFs with large pore volume and/or various topologies can often be challenging due to multistep organic syntheses involved for linker preparation. In this report, a modular MOF synthesis strategy is developed by utilizing the coordination and covalent bonds formation in one-pot strategy where monoacid-based ligands reacted to form ditopic ligands, which then assembled into a three-dimensional MOF with Zr clusters.

Vanadium Catalyst on Isostructural Transition Metal, Lanthanide, and Actinide Based Metal-Organic Frameworks for Alcohol Oxidation.

The understanding of the catalyst-support interactions has been an important challenge in heterogeneous catalysis since the supports can play a vital role in controlling the properties of the active species and hence their catalytic performance. Herein, a series of isostructural mesoporous metal-organic frameworks (MOFs) based on transition metals, lanthanides, and actinides (Zr, Hf, Ce, Th) were investigated as supports for a vanadium catalyst. The vanadium species was coordinated to the oxo groups of the MOF node in a single-ion fashion, as determined by single-crystal X-ray diffraction, diffuse reflectance infrared Fourier transform spectroscopy, and diffuse reflectance UV-vis spectroscopy.

Topology and porosity control of metal-organic frameworks through linker functionalization.

Tetratopic organic linkers have been extensively used in Zr-based metal-organic frameworks (MOFs) where diverse topologies have been observed. Achieving meticulous control over the topologies to tune the pore sizes and shapes of the resulting materials, however, remains a great challenge. Herein, by introducing substituents to the backbone of tetratopic linkers to affect the linker conformation, phase-pure Zr-MOFs with different topologies and porosity were successfully obtained under the same synthetic conditions.

Porosity Dependence of Compression and Lattice Rigidity in Metal-Organic Framework Series.

Porous materials, including metal-organic frameworks (MOFs), are known to undergo structural changes when subjected to applied hydrostatic pressures that are both fundamentally interesting and practically relevant. With the rich structural diversity of MOFs, the development of design rules to better understand and enhance the mechanical stability of MOFs is of paramount importance. In this work, the compressibilities of seven MOFs belonging to two topological families (representing the most comprehensive study of this type to date) were evaluated using in situ synchrotron X-ray powder diffraction of samples within a diamond anvil cell.

Exploiting π-π Interactions to Design an Efficient Sorbent for Atrazine Removal from Water.

The United States Environmental Protection Agency (EPA) recognizes atrazine, a commonly used herbicide, as an endocrine disrupting compound. Excessive use of this agrochemical results in contamination of surface and ground water supplies via agricultural runoff. Efficient removal of atrazine from contaminated water supplies is paramount.

Linker Competition within a Metal-Organic Framework for Topological Insights.

Efforts toward predictive topology within the design and synthesis of metal-organic frameworks (MOFs) have been extensively studied. Herein, we report an investigation of a linker competition for the nucleation of a Zr-based mixed linker MOF. By varying the relative additions of two linkers and introducing prior seeding to the system, we discern that the scu topology is the kinetic product of the two competing linkers.

A Flexible Metal-Organic Framework with 4-Connected Zr Nodes.

Zr-based metal-organic frameworks (MOFs) have been known for their excellent stability; however, due to the high connectivity of the Zr nodes, it is challenging to introduce flexibility into Zr-MOFs. Here we present a flexible Zr-MOF named NU-1400 comprising 4-connected Zr nodes and tetratopic linkers. It exhibits guest-dependent structural flexibility with up to 48% contraction in the unit cell volume as evidenced by single-crystal X-ray diffraction studies.