Recent Progress in 2D Metal-Organic Framework-Related Materials

2D metal-organic frameworks-based (2D MOF-related) materials benefit from variable topological structures, plentiful open active sites, and high specific surface areas, demonstrating promising applications in gas storage, adsorption and separation, energy conversion, and other domains. In recent years, researchers have innovatively designed multiple strategies to avoid the adverse effects of conventional methods on the synthesis of high-quality 2D MOFs. This review focuses on the latest advances in creative synthesis techniques for 2D MOF-related materials from both the top-down and bottom-up perspectives. Subsequently, the strategies are categorized and summarized for synthesizing 2D MOF-related composites and their derivatives. Finally, the current challenges are highlighted faced by 2D MOF-related materials and some targeted recommendations are put forward to inspire researchers to investigate more effective synthesis methods.

Principles of Design and Synthesis of Metal Derivatives from MOFs

Materials derived from metal-organic frameworks (MOFs) have demonstrated exceptional structural variety and complexity and can be synthesized using low-cost scalable methods. Although the inherent instability and low electrical conductivity of MOFs are largely responsible for their low uptake for catalysis and energy storage, a superior alternative is MOF-derived metal-based derivatives (MDs) as these can retain the complex nanostructures of MOFs while exhibiting stability and electrical conductivities of several orders of magnitude higher. The present work comprehensively reviews MDs in terms of synthesis and their nanostructural design, including oxides, sulfides, phosphides, nitrides, carbides, transition metals, and other minor species. The focal point of the approach is the identification and rationalization of the design parameters that lead to the generation of optimal compositions, structures, nanostructures, and resultant performance parameters. The aim of this approach is to provide an inclusive platform for the strategies to design and process these materials for specific applications. This work is complemented by detailed figures that both summarize the design and processing approaches that have been reported and indicate potential trajectories for development. The work is also supported by comprehensive and up-to-date tabular coverage of the reported studies.

Confinement Effects in Well-Defined Metal-Organic Frameworks (MOFs) for Selective CO2 Hydrogenation: A Review

Decarbonization has become an urgent affair to restrain global warming. CO₂ hydrogenation coupled with H₂ derived from water electrolysis is considered a promising route to mitigate the negative impact of carbon emission and also promote the application of hydrogen. It is of great significance to develop catalysts with excellent performance and large-scale implementation. In the past decades, metal-organic frameworks (MOFs) have been widely involved in the rational design of catalysts for CO₂ hydrogenation due to their high surface areas, tunable porosities, well-ordered pore structures, and diversities in metals and functional groups. Confinement effects in MOFs or MOF-derived materials have been reported to promote the stability of CO₂ hydrogenation catalysts, such as molecular complexes of immobilization effect, active sites in size effect, stabilization in the encapsulation effect, and electron transfer and interfacial catalysis in the synergistic effect. This review attempts to summarize the progress of MOF-based CO₂ hydrogenation catalysts up to now, and demonstrate the synthetic strategies, unique features, and enhancement mechanisms compared with traditionally supported catalysts. Great emphasis will be placed on various confinement effects in CO₂ hydrogenation. The challenges and opportunities in precise design, synthesis, and applications of MOF-confined catalysis for CO₂ hydrogenation are also summarized.

MOF-Derived Cu@N-C Catalyst for 1,3-Dipolar Cycloaddition Reaction

Cu(im)2-derived Cu@N-C composites were used for the first time as efficient heterogeneous catalysts for one-pot 1,3-dipolar cycloaddition of terminal alkynes, aryl halides, and sodium azide to preparation of 1,4-disubstituted 1,2,3-triazoles with broad substrate scope and high yields. The catalyst can be easily reused without the changes of structure and morphology, and the heterogeneity nature was confirmed from the catalyst recyclability and metal leaching test.

Metal organic framework derived Zn/N co-doped hydrophilic porous carbon for efficient solid phase microextraction of polar phenols

MOF-derived zink and nitrogen co-doped porous carbon (ZNPC) was synthesized through the pyrolysis of MOF-5-NH₂ and used as a solid-phase microextraction (SPME) coating material. Coupled with gas chromatography-mass spectrometry (GC-MS), headspace SPME (HS-SPME) based on ZNPC was adopted for the determination of phenols in food samples. The co-existence of N and Zn in ZNPC endows the derived carbon superior hydrophilicity, which is highly beneficial for phenols capture. After optimizing the conditions of extraction and desorption, a sensitive analytical method was established with low limits of detections (LODs, 0.73-2.3 ng g^-1) and wide linear ranges (5-5000 ng g^-1). Both the intra-fiber repeatability (RSDs from 2.8-7.3%) and inter-fiber reproducibility (RSDs from 9.7-11.7%) were satisfactory. The established method was applied to phenol determination in beef jerky and duck neck with satisfactory recoveries of 81.2-120.4% and RSDs of 2.8-9.9%, which met well with the requirement of practical application.

Metal-organic framework derived nanomaterials for electrocatalysis: recent developments for CO2 and N2 reduction

In recent years, we are witnessing a substantially growing scientific interest in MOFs and their derived materials in the field of electrocatalysis. MOFs acting as a self-sacrificing template offer various advantages for the synthesis of carbon-rich materials, metal oxides, and metal nanostructures containing graphitic carbon-based materials benefiting from the high surface area, porous structure, and abundance of metal sites and organic functionalities. Yet, despite recent advancement in the field of MOF-derived materials, there are still several significant challenges that should be overcomed, to obtain better control and understanding on the factors determining their chemical, structural and catalytic nature. In this minireview, we will discuss recently reported advances in the development of promising methods and strategies for the construction of functional MOF-derived materials and their application as highly-active electrocatalysts for two important energy-related reactions: nitrogen reduction to produce ammonia, and CO2 reduction into carbon-based fuels. Moreover, a discussion containing assessments and remarks on the possible future developments of MOF-derived materials toward efficient electrocatalysis is included.

Designed Fabrication of Polymer-Mediated MOF-Derived Magnetic Hollow Carbon Nanocages for Specific Isolation of Bovine Hemoglobin

It is highly required to develop well-designed separation materials for the specific isolation of certain proteins in proteomic research. Herein, the new type of metal-organic framework (MOF)-derived polymer-mediated magnetic hollow nanocages was fabricated via stress-induced orientation contraction, which was further applied for specific enrichment of proteins. The core-shell nanocomposites comprised of polymer-mediated ZIF-67 cores and polydopamine (PDA) shells, after annealing, generated magnetic hollow carbon nanocages with hierarchical pores and structures. Particularly, the magnetic carbonized PDA@F127/ZIF-67 hollow nanocages exhibited a remarkable adsorption capacity toward bovine hemoglobin (BHB) up to 834.3 mg g^-1, which was significantly greater than that of the directed carbonized ZIF-67 nanoparticles. The results also exhibited the notable specificity of the obtained nanocages on complex biosamples, including intact mixed proteins and fetal calf serum. The hierarchically hollow porous structure greatly improves the specific surface area and reduces the mass transfer resistance, leading to enhanced high adsorption for target protein BHB. This novel method will be promising for the applications in purification and enrichment of biomacromolecules for complex biosamples, which successfully solve the problem of low adsorption efficiency and tedious separating process of the previous MOF-derived materials.

Three MOF-Templated Carbon Nanocomposites for Potential Platforms of Enzyme Immobilization with Improved Electrochemical Performance

An efficient and facile metal-organic framework (MOF)-template strategy for preparing carbon nanocomposites has been developed. First of all, a series of metal ions, including Fe³⁺, Zr⁴⁺, and La³⁺, were respectively connected with 2-aminoterephthalate (H₂ATA) to form three metal-organic frameworks (MOFs) and then three novel MOF-derived materials were obtained by annealing them at 550 °C under N₂ atmosphere. The morphologies and microstructure results showed that they still retained the original structure of MOFs and formed carbon-supported metal oxide hybrid nanomaterials. Interestingly, it was found that La-MOF-NH₂ and its derived materials were first reported, which had wool-ball-like structure formed by many streaky-shaped particles intertwining each other. Furthermore, these MOF-derived materials were all successfully used as effective immobilization matrixes of acetylcholinesterase (AChE) to construct biosensors for the detection of methyl parathion. Especially, [La-MOF-NH₂]_N2 with wool-ball-like structure not only provided more active sites of multicontents to increase AChE immobilization amount but also facilitated the accessibility of electron transfer and shorten their diffusion length on the surface of electrode. Under optimal conditions, the biosensor based on [La-MOF-NH₂]_N2 displayed the widest linear range of 1.0 × 10^-13-5.0 × 10^-9 g mL^-1 and the lowest detection limit of 5.8 × 10^-14 g mL^-1 in three biosensors. This study illustrates the feasibility and the potential of a series of MOF-derived materials for biosensors with improved electrochemical performance.

Metal-Organic Framework-Derived Materials for Sodium Energy Storage

Recently, sodium-ion batteries (SIBs) are extensively explored and are regarded as one of the most promising alternatives to lithium-ion batteries for electrochemical energy conversion and storage, owing to the abundant raw material resources, low cost, and similar electrochemical behavior of elemental sodium compared to lithium. Metal-organic frameworks (MOFs) have attracted enormous attention due to their high surface areas, tunable structures, and diverse applications in drug delivery, gas storage, and catalysis. Recently, there has been an escalating interest in exploiting MOF-derived materials as anodes for sodium energy storage due to their fast mass transport resulting from their highly porous structures and relatively simple preparation methods originating from in situ thermal treatment processes. In this Review, the recent progress of the sodium-ion storage performances of MOF-derived materials, including MOF-derived porous carbons, metal oxides, metal oxide/carbon nanocomposites, and other materials (e.g., metal phosphides, metal sulfides, and metal selenides), as SIB anodes is systematically and completely presented and discussed. Moreover, the current challenges and perspectives of MOF-derived materials in electrochemical energy storage are discussed.