One-dimensional metal-organic frameworks for electrochemical applications

Revolutionizing wastewater treatment: A review on the role of advanced functional bio-based hydrogels

Water contamination poses a significant challenge to environmental and public health, necessitating sustainable wastewater treatment solutions. Adsorption is one of the most widely used techniques for purifying water, as it effectively removes contaminants by transferring them from the liquid phase to a solid surface. Bio-based hydrogel adsorbents are gaining popularity in wastewater treatment due to their versatility in fabrication and modification methods, which include blending, grafting, and crosslinking. Owning to their unique structure and large surface area, modified hydrogels containing reactive groups like amino, hydroxyl, and carboxyl, or functionalized hydrogels with inorganic nanoparticles particularly graphene nanomaterials, have demonstrated promising adsorption capabilities for both inorganic and organic contaminants. Bio-based hydrogels have excellent physicochemical properties and are non-toxic, environmentally friendly, and biodegradable, making them extremely effective at removing contaminants like heavy metal ions, dyes, pharmaceutical pollutants, and organic micropollutants. The versatility of hydrogels allows for various forms to be used, such as films, beads, and nanocomposites, providing flexibility in handling different contaminants like dyes, radionuclides, and heavy metals. Additionally, researchers also have shown the potential for recycling and regenerating post-treatment hydrogels. This approach not only addresses the challenges of wastewater treatment but also offers sustainable and effective solutions for mitigating water pollution.

Superlong Metal-Organic Framework Nanowire Fabricated via Steam-Assisted Conversion

1D nanomaterials have attracted great attention due to their outstanding anisotropic and linear structures. A facile method is developed to fabricate 1D copper metal-organic framework nanowires (Cu-MOF-NW) through steam-assisted conversion from Cu-MOF precursors. During the steam-assisted conversion, Cu-MOF precursor gradually dissolves in methanol steam, and then recrystallized into Cu-MOF-NW, which shows high aspect ratio of about 600 and identical crystal structure of MOF-74. As-prepared Cu-MOF-NW with multiscale porous structure can effectively remove cationic dyes even in dye mixture. Moreover, Cu-MOF-NW, as an ideal template, is calcined to form Cu nanoparticle-doped carbon nanofiber with maintaining its 1D morphology, which shows excellent electrocatalytic activity for the non-enzymatic sensing of glucose.

Engineering organic polymers as emerging sustainable materials for powerful electrocatalysts

Cost-effective and high-efficiency catalysts play a central role in various sustainable electrochemical energy conversion technologies that are being developed to generate clean energy while reducing carbon emissions, such as fuel cells, metal-air batteries, water electrolyzers, and carbon dioxide conversion. In this context, a recent climax in the exploitation of advanced earth-abundant catalysts has been witnessed for diverse electrochemical reactions involved in the above mentioned sustainable pathways. In particular, polymer catalysts have garnered considerable interest and achieved substantial progress very recently, mainly owing to their pyrolysis-free synthesis, highly tunable molecular composition and microarchitecture, readily adjustable electrical conductivity, and high stability. In this review, we present a timely and comprehensive overview of the latest advances in organic polymers as emerging materials for powerful electrocatalysts. First, we present the general principles for the design of polymer catalysts in terms of catalytic activity, electrical conductivity, mass transfer, and stability. Then, the state-of-the-art engineering strategies to tailor the polymer catalysts at both molecular (i.e., heteroatom and metal atom engineering) and macromolecular (i.e., chain, topology, and composition engineering) levels are introduced. Particular attention is paid to the insightful understanding of structure-performance correlations and electrocatalytic mechanisms. The fundamentals behind these critical electrochemical reactions, including the oxygen reduction reaction, hydrogen evolution reaction, CO2 reduction reaction, oxygen evolution reaction, and hydrogen oxidation reaction, as well as breakthroughs in polymer catalysts, are outlined as well. Finally, we further discuss the current challenges and suggest new opportunities for the rational design of advanced polymer catalysts. By presenting the progress, engineering strategies, insightful understandings, challenges, and perspectives, we hope this review can provide valuable guidelines for the future development of polymer catalysts.

Recent insights on the use of modified Zn-based catalysts in eCO2RR

Converting CO2 into valuable chemicals can provide a new path to mitigate the greenhouse effect, achieving the aim of "carbon neutrality" and "carbon peaking". Among numerous electrocatalysts, Zn-based materials are widely distributed and cheap, making them one of the most promising electrocatalyst materials to replace noble metal catalysts. Moreover, the Zn metal itself has a certain selectivity for CO. After appropriate modification, such as oxide derivatization, structural reorganization, reconstruction of the surfaces, heteroatom doping, and so on, the Zn-based electrocatalysts can expose more active sites and adjust the d-band center or electronic structure, and the FE and stability of them can be effectively improved, and they can even convert CO2 to multi-carbon products. This review aims to systematically describe the latest progresses of modified Zn-based electrocatalyst materials (including organic and inorganic materials) in the electrocatalytic carbon dioxide reduction reaction (eCO2RR). The applications of modified Zn-based catalysts in improving product selectivity, increasing current density and reducing the overpotential of the eCO2RR are reviewed. Moreover, this review describes the reasonable selection and good structural design of Zn-based catalysts, presents the characteristics of various modified zinc-based catalysts, and reveals the related catalytic mechanisms for the first time. Finally, the current status and development prospects of modified Zn-based catalysts in eCO2RR are summarized and discussed.

Progress and Perspectives on Promising Covalent-Organic Frameworks (COFs) Materials for Energy Storage Capacity

In recent years, a new class of highly crystalline advanced permeable materials covalent-organic frameworks (COFs) have garnered a great deal of attention thanks to their remarkable properties, such as their large surface area, highly ordered pores and channels, and controllable crystalline structures. The lower physical stability and electrical conductivity, however, prevent them from being widely used in applications like photocatalytic activities and innovative energy storage and conversion devices. For this reason, many studies have focused on finding ways to improve upon these interesting materials while also minimizing their drawbacks. This review article begins with a brief introduction to the history and major milestones of COFs development before moving on to a comprehensive exploration of the various synthesis methods and recent successes and signposts of their potential applications in carbon dioxide (CO2 ) sequestration, supercapacitors (SCs), lithium-ion batteries (LIBs), and hydrogen production (H2 -energy). In conclusion, the difficulties and potential of future developing with highly efficient COFs ideas for photocatalytic as well as electrochemical energy storage applications are highlighted.

Modulating Electronic Structure of PtCo-Ptrich Nanowires with Ru atoms for Boosted Hydrogen Evolution Catalysis

Rational design and development of highly efficient hydrogen evolution reaction (HER) electrocatalysts is of great significance for the development of green water electrolysis hydrogen production technology. Ru-engineered 1D PtCo-Ptrich nanowires (Ru-Ptrich Co NWs) are fabricated by a facile electrodeposition method. The rich Pt surface on 1D Pt3 Co contributes to the fully exposed active sites and enhanced intrinsic catalytic activity (co-engineered by Ru and Co atoms) for HER. The incorporation of Ru atoms can not only accelerate the water dissociation in alkaline condition to provide sufficient H* but also modulate the electronic structure of Pt to achieve optimized H* adsorption energy. As a result, Ru-Ptrich Co NWs have exhibited ultralow HER overpotentials (η) of 8 and 112 mV to achieve current densities of 10 and 100 mA cm-2 in 1 m KOH, respectively, which far exceed those of commercial Pt/C catalyst (η10  = 29 mV, η100  = 206 mV). Density functional theory (DFT) calculations further demonstrate that the incorporated Ru atoms possess strong water adsorption capacity (-0.52 vs -0.12 eV for Pt), facilitating water dissociation. The Pt atoms in the outermost Pt-rich skin of Ru-Ptrich Co NWs achieve optimized H* adsorption free energy (ΔGH* ) of -0.08 eV, boosting hydrogen generation.

Phosphorus-Doped directly interconnected networks of amorphous Metal-Organic framework nanowires for efficient methanol oxidation

Developing high-performance and low-cost electrocatalysts toward methanol oxidation reaction (MOR) is essential for fuel cell applications. Herein, we report a defect engineering strategy integrating amorphization and phosphorization to construct directly interconnected networks of amorphous NiCo-based metal-organic framework nanowires (a-NiCo-MOFNWs) with phosphorus (P) doping. The resulting P-doped a-NiCo-MOFNWs (a-NiCo-MOFNWs-P) network displays superior MOR efficiency and long-term durability over 1000 cyclic voltammetry (CV) measurements. The special structure of directly interconnected networks and the synergistic effect between the amorphous MOFs and dispersed phosphorus species give rise to abundant exposed active sites, accelerated electron transport, and increased porosity for mass transfer, thus boosting the reaction kinetics of MOR. This work provides additional insights into the network assembly and structural evolution of one-dimensional (1D) MOFs, and also opens up new avenues for the design of highly reactive and robust non-precious metal-based electrocatalysts.

Metal-organic frameworks-derived layered double hydroxides: From controllable synthesis to various electrochemical energy storage/conversion applications

Over the past years, metal-organic frameworks (MOF) have been directly used as electrodes or as a precursor for MOF-derived materials in energy storage and conversion systems. In the wide range of existing MOF derivatives, MOF-derived layered double hydroxides (LDHs) are determined to be promising materials due to their unique structure and features. However, MOF-derived LDHs (MDL) materials can suffer from insufficient intrinsic conductivity and agglomeration during formation. Various techniques and approaches were designed and applied to tackle these problems, such as using ternary LDHs, ion-doping, sulphurization, phosphorylation, selenization, direct growth, and conductive substrates. All the mentioned enhancement techniques aim to create the ideal electrode materials with maximum performance. In this review, we gathered and discussed the most recent progressive advances, different synthesis methodologies, unsolved challenges, applications, and electrochemical and electrocatalytic performance of MDL materials. We hope this work will be a reliable source for future progress and synthesis of these materials.

Enhancing the Photocatalytic Degradation Efficiency of Dyes of Copper-Based Metal-Organic Frameworks through a Dimension-Induced Structural Strategy

Photocatalytic degradation of pollutants is an effective environment purification strategy. Metal-organic frameworks (MOFs) have attracted extensive attention in the field of photocatalysis owing to their structural diversity, uniform cavity, and large specific surface area. However, poor electrical conductivity, light absorption, and water stability restrict their development. The tailorable structure of MOFs may effectively overcome these limitations. Herein, three Cu-based MOFs (complexes 1-3) with one-dimensional (1D), two-dimensional (2D), and three-dimensional (3D) structures, respectively, were successfully prepared by introducing different uncoordinated ligands and adjusting the ligand/metal salt ratio. Among them, complex 1 with a 1D chain was constructed as a typical J-type aggregation by π-π stacking interactions between adjacent naphthalene rings. This intermolecular aggregation mode enhances strong exciton coupling between conjugated rings, reduces the transition energy, expands the intrinsic light absorption edge, and provides a channel for electron transport, thus improving the charge-separation efficiency. As expected, complex 1 with a 1D chain structure exhibited excellent Fenton-like catalytic activity. The apparent reaction rates were 3.2 and 2.0 times higher than those of 2D and 3D MOFs, respectively.

Hotspots analysis and perspectives of Prussian blue analogues (PBAs) in environment and energy in recent 20 years by CiteSpace

Prussian blue analogs (PBAs), a type of metal-organic frameworks (MOFs), have attracted much attention because of their large specific surface area, high porosity, easy synthesis, and low cost. This paper presents the first review of PBAs by applying the bibliometric visualization software CiteSpace. The co-occurrence, co-citation, and clustering analysis of 2214 articles in the Web of Science database on the topic of "Prussian blue analogs" over the past 20 years were performed. The results provide a comprehensive overview of the evolution of the research hotspots for this material, and most importantly, it is identified that the research hotspots and trends for PBAs materials are concentrated in the environmental and energy fields. For example, the material is used as an adsorbent or catalyst to reduce pollutants, produce clean energy, or for energy storage applications such as batteries or supercapacitors. Finally, some outlooks are provided on the future research trends of this material in the environmental and energy fields, presenting the challenges faced by this material. For instance, the conductivity and corrosion resistance of the material needs to be improved and secondary contamination should be decreased or even avoided. It is believed that this paper would provide a comprehensive, systematic, and dynamic overview of the research of PBAs, and promote the future research of PBAs in the fields of environment and energy.

Facile Synthesis of 4,4'-biphenyl Dicarboxylic Acid-Based Nickel Metal Organic Frameworks with a Tunable Pore Size towards High-Performance Supercapacitors

Metal-organic frameworks (MOFs) have attracted significant research interest for supercapacitor applications due to their high-tunable conductivity and their structure’s pore size. In this work, we report a facile one-step hydrothermal method to synthesize nickel-based metal-organic frameworks (MOF) using organic linker 4,4′-biphenyl dicarboxylic acid (BPDC) for high-performance supercapacitors. The pore size of the Ni-BPDC-MOF nanostructure is tuned through different synthesization temperatures. Among them, the sample synthesized at 180 °C exhibits a nanoplate morphology with a specific surface area of 311.99 m²·g⁻¹, a pore size distribution of 1–40 nm and an average diameter of ~29.2 nm. A high specific capacitance of 488 F·g⁻¹ has been obtained at a current density of 1.0 A·g⁻¹ in a 3 M KOH aqueous electrolyte. The electrode shows reliable cycling stability, with 85% retention after 2000 cycles. The hydrothermal process Ni-BPDC-MOF may provide a simple and efficient method to synthesize high-performance hybrid MOF composites for future electrochemical energy storage applications.

Superhydrophobic modular cryogel with variable magnetic-actuated motion direction for discrete small-scale oil spill cleanup

Smart superhydrophobic sorbents are in high demand for cleaning oil spills that could endanger the aquatic ecosystem. Herein, we demonstrated the fabrication of a superhydrophobic and magnetic modular cryogel (SNS@Fe-PSC) containing three starch-based modules, namely, a superhydrophobic nano-coating, a magnetic nanocomposite insertion, and a high-strength starch/polyvinyl alcohol composite substrate. The surface chemical composition and hierarchical micro/nanostructures of this material were investigated in detail. The modular cryogel had a high water contact angle (>151°) and low sliding angle (<9°), as well as excellent water-repellent, self-cleaning, and anti-fouling properties. This material also exhibited good durability owing to its stable chemical bonding and structural support. SNS@Fe-PSC could be applied to remove oil from water effectively. Moreover, the magnetic module (saturation magnetization, 5.04 emu/g) allowed the as-obtained material to be propelled and controlled by a magnet on the surface of water. Variable magnetic-actuated motion direction could be realized by adjusting the position and amount of magnetic modules inserted to the cryogel.

Magnetic UiO-66 functionalized with 4,4'-diamino-2,2'-stilbenedisulfonic as a highly recoverable acid catalyst for the synthesis of 4H-chromenes in green solvent

According to 4H-chromenes importance, we synthesized a novel magnetic UiO-66 functionalized with 4,4′-diamino-2,2′-stilbenedisulfonic as an efficient and reusable solid acid catalyst for synthesizing 4H-chromene skeletons via a one-pot three components reaction in a green solvent. The structure of the synthesized catalyst was confirmed by various techniques including FT-IR, XRD, BET, TGA, TEM, EDX, and SEM, and also the product yields were obtained in 83–96% of yields for all the reactions and under mild conditions. The reported procedure presents an environmentally friendly approach for synthesizing a significant number of 4H-chromene derivatives. Correspondingly, MOF-based catalyst makes it easy to separate from reaction media and reuse in the next runs.

Metal-organic frameworks and their derivatives as electrode materials for Li-ion batteries: a mini review

In recent decades, in order to obtain more excellent performance and wider application of rechargeable lithium-ion batteries (LIBs), researchers have been exploring potential electrode materials. MOFs possess attractive features, such...