Ultrafine Pt Nanoparticles and Amorphous Nickel Supported on 3D Mesoporous Carbon Derived from Cu-Metal-Organic Framework for Efficient Methanol Oxidation and Nitrophenol Reduction

Quaternization of a Triphenylamine-Based Conjugated Porous Organic Polymer to Immobilize PtCl62- for the Photocatalytic Reduction of 4-Nitrophenol

Photocatalytic reduction of 4-nitrophenol (4-NP) for converting it to nontoxic 4-aminophenol (4-AP) is one of the most efficient approaches for removing toxic 4-NP. Using porous organic polymers (POPs) as the support to immobilize noble metal catalysts has exhibited remarkable reduction performance but is rarely reported. Herein, a cationic triphenylamine-based POP was synthesized by quaternization to immobilize PtCl62- to prepare an efficient photocatalyst named DCM-TPA-Pt for the reduction of 4-NP to 4-AP in the presence of NaBH4. Different from reported methods which realize immobilization by doping or complexing, the support and PtCl62- are combined through electrostatic interaction with milder reaction conditions to produce a photocatalyst in this work. DCM-TPA-Pt shows excellent photocatalytic reduction performance, reaching 99.9% conversion within 3 min, and its pseudo-first-order constant is 0.0305 s-1, surpassing most of the reported photocatalysts. Moreover, DCM-TPA-Pt also exhibits equal reduction efficiency after five continuous cycles, which highlights its potential utilization in practical applications.

Advancements in Noble Metal-Decorated Porous Carbon Nanoarchitectures: Key Catalysts for Direct Liquid Fuel Cells

Noble-metal nanocrystals have emerged as essential electrode materials for catalytic oxidation of organic small molecule fuels in direct liquid fuel cells (DLFCs). However, for large-scale commercialization of DLFCs, adopting cost-effective techniques and optimizing their structures using advanced matrices are crucial. Notably, noble metal-decorated porous carbon nanoarchitectures exhibit exceptional electrocatalytic performances owing to their three-dimensional cross-linked porous networks, large accessible surface areas, homogeneous dispersion (of noble metals), reliable structural stability, and outstanding electrical conductivity. Consequently, they can be utilized to develop next-generation anode catalysts for DLFCs. Considering the recent expeditious advancements in this field, this comprehensive review provides an overview of the current progress in noble metal-decorated porous carbon nanoarchitectures. This paper meticulously outlines the associated synthetic strategies, precise microstructure regulation techniques, and their application in electrooxidation of small organic molecules. Furthermore, the review highlights the research challenges and future opportunities in this prospective research field, offering valuable insights for both researchers and industry experts.

Polymerization Induced Microphase Separation for the Fabrication of Nanostructured Materials

Polymerization induced microphase separation (PIMS) is a strategy used to develop unique nanostructures with highly useful morphologies through the microphase separation of emergent block copolymers during polymerization. In this process, nanostructures are formed with at least two chemically independent domains, where at least one domain is composed of a robust crosslinked polymer. Crucially, this synthetically simple method is readily used to develop nanostructured materials with the highly coveted co-continuous morphology, which can also be converted into mesoporous materials by selective etching of one domain. As PIMS exploits a block copolymer microphase separation mechanism, the size of each domain can be tightly controlled by modifying the size of block copolymer precursors, thus providing unparalleled control over nanostructure and resultant mesopore sizes. Since its inception 11 years ago, PIMS has been used to develop a vast inventory of advanced materials for an extensive range of applications including biomedical devices, ion exchange membranes, lithium-ion batteries, catalysis, 3D printing, and fluorescence-based sensors, among many others. In this review, we provide a comprehensive overview of the PIMS process, summarize latest developments in PIMS chemistry, and discuss its utility in a wide variety of relevant applications.

Pt-C interactions in carbon-supported Pt-based electrocatalysts

Carbon-supported Pt-based materials are highly promising electrocatalysts. The carbon support plays an important role in the Pt-based catalysts by remarkably influencing the growth, particle size, morphology, dispersion, electronic structure, physiochemical property and function of Pt. This review summarizes recent progress made in the development of carbon-supported Pt-based catalysts, with special emphasis being given to how activity and stability enhancements are related to Pt-C interactions in various carbon supports, including porous carbon, heteroatom doped carbon, carbon-based binary support, and their corresponding electrocatalytic applications. Finally, the current challenges and future prospects in the development of carbon-supported Pt-based catalysts are discussed.

Sputtered Cu-doped NiO thin films as an efficient electrocatalyst for methanol oxidation

The efficient electrocatalysts for direct methanol oxidation play an essential role in the electrochemical energy conversion systems for their application in a wide range of portable applications. Consequently, Cu-doped NiO thin films on fluorine-doped tin oxide (FTO) were successfully prepared by the co-sputtering deposition technique, using various deposition times (300, 600, 900, and 1200 seconds), and producing films of different thicknesses (30, 55, 90, and 120 nm, respectively). X-ray diffraction (XRD) revealed the ideal crystallinity of the structure of the prepared films and was used to observe the effect of the thickness of the films on the crystal size. Energy-dispersive X-ray spectroscopy (EDS) confirmed the purity of the deposited film without any contamination. Field emission scanning electron microscopy (FESEM) images confirmed the film thickness increase with increasing deposition time. The surface roughness value of the Cu-NiO 1200 film was found to be 3.2 nm based on the atomic force microscopy (AFM) measurements. The deposited thin films of different thicknesses have been used as electrocatalysts for methanol oxidation at various concentrations of methanol (0, 0.5, 1, and 2 M), and displayed the highest electrocatalytic performance in 1 M methanol. Cu-doped NiO thin films have the advantage as electrocatalysts where they can be used directly without adding any binder or conducting agents, this is because Cu-doped NiO is deposited with high adhesion and strong electrical contact to the FTO substrate. A clear impact on the catalytic activity with increasing film thickness and a correlation between the film thickness and its catalytic activity was observed. The current density increased by about 60% for the Cu-NiO 1200 sample compared to Cu-NiO 300 sample, with the lowest onset potential of 0.4 V vs. Ag/AgCl. All deposited thin films of different thicknesses exhibited high stability at 0.6 V in 1 M methanol. This will open the window toward using physical deposition techniques for optimizing the electrocatalytic activity of different catalysts for electrocatalytic applications.

Facile in Situ Transformation of NiOOH into MOF-74(Ni)/NiO OH Heterogeneous Composite for Enchancing Electrocatalytic Methanol Oxidation

A new MOF-74(Ni)/NiOOH heterogeneous composite was synthesized via NiOOH microsphere precursor. The electrocatalytic methanol oxidation reactions' (MOR) performance was assessed. The as-prepared MOF-74(Ni)/NiOOH exhibited excellent activity with high peak current density (27.62 mA·cm^-2) and high mass activity (243.8 mA·mg^-1). The enhanced activity could be a result of the synergistic effect of the MOF-74(Ni)/NiOOH heterocomposite providing more exposed active sites, a beneficial diffusion path between the catalyst surface and electrolyte, and improved conductivity, favorable for improving MOR performance.

General Method for Synthesizing Effective and Durable Electrocatalysts Derived from Cellulose for Microbial Fuel Cells

Microbial fuel cells (MFCs) can be capable of both wastewater treatment and electricity generation, which necessarily depends on the increasing cathodic performances and stability at low cost to realize industrialization. Herein, cellulose, a commercially available and sustainable material, was oxidized as a carbon precursor to produce the oxygen species synergizing the nitrogen-doped carbon (CON-900) catalyst by a facile in situ nitrogen doping method. The incorporation of nitrogen and oxygen with a high content creates more active centers. Meanwhile, the hierarchical porosity of CON-900 contributes to a high specific surface area (652 m² g^-1) and the exposure of accessible active sites. As expected, CON-900 exhibits considerable activity for the oxygen reduction reaction, excellent operating stability, and high poisoning resistance. In addition, the MFC fabricated with CON-900 as a cathode catalyst demonstrates a maximum power density of 1014 ± 23 mW m^-2, which is comparable with that of the Pt/C cathode (1062 ± 14 mW m^-2). This work offers a facile and versatile strategy for various biomass materials to develop low-cost and high-efficiency carbon-based catalysts for MFCs and beyond.

Aluminum Doping and Nanostructuring Enabled Designing of Magnetically Recoverable Hexaferrite Catalysts

We demonstrate an approach based on substituting a magnetic cation with a carefully chosen isovalent non-magnetic cation to derive catalytic activity from otherwise catalytically inactive magnetic materials. Using the model system considered, the results illustratively present that the catalytically inactive but highly magnetic strontium hexaferrite (SrFe₁₂O₁₉; SFO) system can be transformed into a catalytically active system by simply replacing some of the magnetic cation Fe³⁺ by a non-magnetic cation Al³⁺ in the octahedral coordination environment in the SFO nanocrystals. The intrinsic SFO and Al-doped SrFe₁₂O₁₉ (SrFe_11.5Al_0.5O₁₉; Al-SFO) nanomaterials were synthesized using a simple, eco-friendly tartrate-gel technique, followed by thermal annealing at 850 °C for 2 h. The SFO and Al-SFO were thoroughly characterized for their structure, phase, morphology, chemical bonding, and magnetic characteristics using X-ray diffraction, Fourier-transform infrared spectroscopy, and vibrating sample magnetometry techniques. Catalytic performance evaluated toward 4-nitrophenol, which is the toxic contaminant at pharmaceutical industries, reduction reaction using NaBH₄ (mild reducing agent), the Al-doped SFO samples exhibit a reasonably good performance compared to intrinsic SFO. The results indicate that the catalytic activity of Al-SFO is due to Al-ions occupying the octahedral sites of the hexaferrite lattice; as these sites are on the surface of the catalyst, they facilitate electron transfer. Furthermore, surface/interface characteristics of nanocrystalline Al-SFO coupled with magnetic properties facilitate the catalyst recovery by simple, inexpensive methods while readily allowing the reusability. Moreover, the activity remains the same even after five successive cycles of experiments. Deriving the catalytic activity from otherwise inactive compounds as demonstrated in the optimized, engineered nanoarchitecture of Al-doped-Sr-hexaferrite may be useful in adopting the approach in exploring further options and designing inexpensive and recyclable catalytic materials for future energy and environmental technologies.

Self-supporting CoP-C nanosheet arrays derived from a metal-organic framework as synergistic catalysts for efficient water splitting

Here, a new strategy that combines accessible active sites and multiphase synergy in a simple process is developed for constructing bifunctional electrocatalysts toward overall water splitting. By using metal-organic framework (MOF) nanosheets hydrothermally grown on pre-oxidized nickel foam (denoted by Co₂(OH)₂(BDC)/NiO/NF) as a precursor, two novel heterogeneous nanosheet arrays including a cobalt phosphide nanoparticle embedded carbon nanotube nanosheet array supported by phosphorized nickel foam (denoted by CoP-CNT/Ni₂P/NF) and a cobalt phosphide nanorod decorated carbon nanosheet array supported by oxidized nickel foam (denoted by CoP-C/NiO/NF) are prepared. Both were confirmed to be highly efficient for hydrogen and oxygen evolution reactions. In particular, CoP-C/NiO/NF exhibits higher catalytic activity toward the hydrogen evolution reaction (η₁₀₀ = -131 mV), promoted by the synergy of oxidized nickel foam. CoP-CNT/Ni₂P/NF performs better in the oxygen evolution reaction (η₅₀ = 301 mV), benefiting mainly from its improved electrochemically active surface area. The two catalysts match well in overall water splitting with satisfactory activity (η₁₀ = 1.57 V) and stability when directly applied in a two-electrode cell. This method will bring new inspiration to maximize the electrocatalytic efficiency of MOF-derived catalysts for energy conversion applications in the future.

A Type of MOF-Derived Porous Carbon with Low Cost as an Efficient Catalyst for Phenol Hydroxylation

Using MOF-5 as a template, the porous carbon (MDPC-600) possessing high specific surface area was obtained after carbonization and acid washing. After MDPC-600 was loaded with Cu ions, the catalyst Cu/MDPC-600 was acquired by heat treatment under nitrogen atmosphere. The catalyst was characterized by X-ray powder diffraction (XRD), N2 physical adsorption (BET), field emission electron microscope (SEM), energy spectrum, and transmission electron microscope (TEM). The results show that the Cu/MDPC-600 catalyst prepared by using MOF-5 as the template has a very high specific surface area, and Cu is uniformly supported on the carrier. The catalytic hydrogen peroxide oxidation reaction of phenol hydroxylation was investigated and exhibits better catalytic activity and stability in the phenol hydroxylation reaction. The catalytic effect was best when the reaction temperature was 80°C, the reaction time was 2 h, and the amount of catalyst was 0.05 g. The conversion rate of phenol was 47.6%; the yield and selectivity of catechol were 37.8% and 79.4%, respectively. The activity of the catalyst changes little after three cycles of use.

Recent Progress in Metal-Organic Framework-Derived Nanostructures in the Removal of Volatile Organic Compounds

Air is the most crucial and life-supporting input from nature to the living beings of the planet. The composition and quality of air significantly affects human health, either directly or indirectly. The presence of some industrially released gases, small particles of anthropogenic origin, and the deviation from the normal composition of air from the natural condition causes air pollution. Volatile organic compounds (VOCs) are common contaminants found as indoor as well as outdoor pollutants. Such pollutants represent acute or chronic health hazards to the human physiological system. In the environment, such polluted gases may cause chemical or photochemical smog, leading to detrimental effects such as acid rain, global warming, and environmental pollution through different routes. Ultimately, this will propagate into the food web and affect the ecosystem. In this context, the efficient removal of volatile organic compounds (VOCs) from the environment remains a major threat globally, yet satisfactory strategies and auxiliary materials are far from being in place. Metal–organic frameworks (MOFs) are known as an advanced class of porous coordination polymers, a smart material constructed from the covalently bonded and highly ordered arrangements of metal nodes and polyfunctional organic linkers with an organic–inorganic hybrid nature, high porosities and surface areas, abundant metal/organic species, large pore volumes, and elegant tunability of structures and compositions, making them ideal candidates for the removal of unwanted VOCs from air. This review summarizes the fundamentals of MOFs and VOCs with recent research progress on MOF-derived nanostructures/porous materials and their composites for the efficient removal of VOCs in the air, the remaining challenges, and some prospective for future efforts.

Bifunctional Pd@RhPd Core-Shell Nanodendrites for Methanol Electrolysis

Methanol electrolysis is a promising strategy to achieve energy-saving and efficient electrochemical hydrogen (H₂) production. In this system, the advanced electrocatalysts with high catalytic performance for both the methanol oxidation reaction (MOR) and hydrogen evolution reaction (HER) are highly desirable. Inspired by the complementary catalytic properties of rhodium (Rh) and palladium (Pd) for MOR and HER, herein, several Pd core-RhPd alloy shell nanodendrites (Pd@RhPd NDs) are synthesized through the galvanic replacement reaction between Pd nanodendrites (Pd NDs) and rhodium trichloride. For MOR, Pd@RhPd NDs exhibit Rh content-determined catalytic activity, in which Pd@Rh_0.07Pd NDs have an optimal combination of oxidation potential and oxidation current due to the synergistic catalytic process of Pd/Rh double active sites. For HER, the introduction of Rh greatly improves the catalytic activity of Pd@RhPd NDs compared to that of Pd NDs, suggesting that Rh is the main activity site for HER. Unlike MOR, however, the HER activity of Pd@RhPd NDs is not sensitive to the Rh content. Using Pd@Rh_0.07Pd NDs as robust bifunctional electrocatalysts, the as-constructed two-electrode methanol electrolysis cell shows a much lower voltage (0.813 V) than that of water electrolysis (1.672 V) to achieve electrochemical H₂ production at 10 mA cm^-2, demonstrating the application prospect of methanol electrolysis for H₂ production.

Controlled growth of ultrafine metal nanoparticles mediated by solid supports

As a unique class of nanomaterials with a high surface-area-to-volume ratio and narrow size distribution, ultrafine metal nanoparticles (UMNPs) have shown exciting properties in many applications, particularly in the field of catalysis. Growing UMNPs in situ on solid supports enables precise control of the UMNP size, and the supports can effectively prevent the aggregation of UMNPs and maintain their high catalytic activity. In this review, we summarize the recent research progress in controlled growth of UMNPs using various solid supports and their applications in catalysis.

Defect engineering and characterization of active sites for efficient electrocatalysis

Electrocatalysis plays a decisive role in various energy-related applications. Engineering the active sites of electrocatalysts is an important aspect to promote their catalytic performance. In particular, defect engineering provides a feasible and efficient approach to improve the intrinsic activities and increase the number of active sites in electrocatalysts. In this review, recent investigations on defect engineering of a wide range of electrocatalysts such as metal-free carbon materials, transition metal oxides, transition metal dichalcogenides and metal-organic frameworks (MOFs) will be summarized. Different defect creation strategies will be outlined, for example, heteroatom doping and removal, plasma irradiation, hydrogenation, amorphization, phase transition and reduction treatment. In addition, we will overview the commonly used advanced characterization techniques that could confirm the existence and identify the detailed structures, types and concentration of defects in electrocatalysts. The defect characterization tools are beneficial for gaining an in-depth understanding of defects on electrocatalysis and thus could reveal the structure-performance relationship. Finally, the major challenges and future development directions on defect engineering of electrocatalysts will be discussed.

Metal–organic framework (MOF)-derived catalysts for chemoselective hydrogenation of nitroarenes

The MOFs derived catalysts conducted in the chemoselective hydrogenation of substituted nitroarenes, including pyrolysis and confined catalyst, are reviewed.

Convenient synthesis of polymetallic metal–organic gels for efficient methanol electro-oxidation

Novel Ni-based AlNiCu-MOG and AB&AlNiCu-MOG composite materials were successfully fabricated, which exhibited superior MOR activities with a current density of 17.1 and 33.24 mA cm⁻², respectively.

A nickel ion-incorporating zinc-mesoporous metal organic framework thin film nanocomposite modified glassy carbon electrode for electrocatalytic oxidation of methanol in alkaline media

In this work, we have successfully synthesized a nickel ion-incorporating zinc-mesoporous metal–organic framework thin films (Zn-mMOFTFs) modified glassy carbon electrode (GCE), Ni/Zn-mMOFTFs/GCE, for electrooxidation of methanol in alkaline solution.

Controlled Preparation of Hollow and Porous Co9S8 Microplate Arrays for High-Performance Hybrid Supercapacitors

The design and controlled preparation of hollow and porous metal sulfide arrays are an important issue for electrochemical energy storage and conversion because of their unique structural merits including large surface areas, shortened diffusion paths, and rich reaction sites. Herein, a hollow and porous Co₉S₈ microplate array (MPA) was successfully fabricated by a facile self-sacrifice template strategy, which involved the uniform growth of a metal-organic framework microplate template on Ni foam (NF) and annealing in air, followed by an anion-exchange reaction with S^2- ions. The resulting Co₉S₈-MPA/NF as a binder-free electrode for a supercapacitor shows a high specific capacitance of 1852 F g^-1 (926 C g^-1) at 1 A g^-1 and an excellent cycling stability (86% retention after 5000 cycles at 20 A g^-1). Moreover, a hybrid supercapacitor (HSC) constructed with Co₉S₈-MPA/NF and activated carbon exhibits an outstanding energy density of 25.49 Wh kg^-1 at a high power density of 800 W kg^-1 and a long-term stability of 92% capacitance retention after 5000 cycles at 10 A g^-1. It is worth noting that the prepared all-solid-state HSC can light a red light-emitting diode for 2 min, proving to be a great practical application prospect. These excellent electrochemical behaviors show that this effective conversion strategy offers more possibilities for the development of high-performance energy storage metal sulfide materials.

Bimetallic Metal-Organic Framework Mediated Synthesis of Ni-Co Catalysts for the Dry Reforming of Methane

Dry reforming of methane (DRM) involves the conversion of CO2 and CH4, the most important greenhouse gases, into syngas, a stoichiometric mixture of H2 and CO that can be further processed via Fischer–Tropsch chemistry into a wide variety of products. However, the devolvement of the coke resistant catalyst, especially at high pressures, is still hampering commercial applications. One of the relatively new approaches for the synthesis of metal nanoparticle based catalysts comprises the use of metal-organic frameworks (MOFs) as catalyst precursors. In this work we have explored MOF-74/CPO-27 MOFs as precursors for the synthesis of Ni, Co and bimetallic Ni-Co metal nanoparticles. Our results show that the bimetallic system produced through pyrolysis of a Ni-Co@CMOF-74 precursor displays the best activity at moderate pressures, with stable performance during at least 10 h at 700 °C, 5 bar and 33 L·h−1·g−1.

Unusual Effect of Trace Water on the Structure and Activity of Nix Co1-x Electrocatalysts for the Methanol Oxidation Reaction

Highly active Ni-based catalysts have attracted much attention but are still facing challenges owing to the immature synthetic method. Herein, polyhedral Ni_x Co_1-x alloy was prepared by a facile modified polyol method in which a trace amount of water could halve the particle size of the alloy. The Ni/Co ratios in Ni_x Co_1-x alloy strictly depended on the used amount of water owing to the different solubilities of the precursors. Among them, the Ni_0.6 Co_0.4 nanoparticles obtained with 70 μL of deionized water exhibited the best performance in the methanol oxidation reaction with a peak current density of 116 mA cm^-2 in the presence of 1 m NaOH+0.5 m CH₃ OH solution, which is higher than those of Ni_0.7 Co_0.3 (80 mA cm^-2 ) and Ni_0.5 Co_0.5 (33 mA cm^-2 ). The excellent performance of Ni_0.6 Co_0.4 is attributed to the unique structure with appropriate Ni/Co ratio, which elongates the C-O bond in methanol and lowers the reaction free energy according to DFT calculations.

Sea-Island-Like Morphology of CuNi Bimetallic Nanoparticles Uniformly Anchored on Single Layer Graphene Oxide as a Highly Efficient and Noble-Metal-Free Catalyst for Cyanation of Aryl Halides

Aryl nitriles are versatile compounds that can be synthesized via transition-metal-mediated cyanation of aryl halides. Most of the supported-heterogeneous catalysts are noble-metals based and there are very limited numbers of efficient non-noble metal based catalysts demonstrated for the cyanation of aryl halides. Herein, bimetallic CuNi-oxide nanoparticles supported graphene oxide nanocatalyst (CuNi/GO-I and CuNi/GO-II) has been demonstrated as highly efficient system for the cyanation of aryl halides with K₄[Fe(CN)₆] as a cyanating agent. Metal-support interaction, defect ratio and synergistic effect with the bimetallic nanocatalyst were investigated. To our delight, the CuNi/GO-I system activity transformed a wide range of substrates such as aryl iodides, aryl bromides, aryl chlorides and heteroaryl compounds (Yields: 95-71%, TON/TOF: 50-38/2 h^-1). Moreover, enhanced catalytic performance of CuNi/GO-I and CuNi/GO-II in reduction of 4-nitropehnol with NaBH₄ was also confirmed (k_app = 18.2 × 10^-3 s^-1 with 0.1 mg of CuNi/GO-I). Possible mechanism has been proposed for the CuNi/GO-I catalyzed cyanation and reduction reactions. Reusability, heterogeneity and stability of the CuNi/GO-I are also found to be good.

Rational Localization of Metal Nanoparticles in Yolk-Shell MOFs for Enhancing Catalytic Performance in Selective Hydrogenation of Cinnamaldehyde

The development of sustainable catalysts to simultaneously improve activity and selectivity remains a challenge. Herein, it is demonstrated that metal nanoparticles (MNPs) can be encapsulated into a yolk-shell metal-organic framework (MOF) with controllable spatial localization to optimize catalytic performance. When the MNPs are located in the void space between the shell and the core of the MOF, the resulting MNPs@MOF composites show both high catalytic activity and selectivity toward the hydrogenation of α,β-unsaturated aldehydes. In particular, the easily recoverable and stable Pt_void @MOF(Y) shows an exceptionally high selectivity of 98.2 % for cinnamyl alcohol at a high conversion of 97 %. The excellent performance can be attributed to easy diffusion of the reactants to access highly exposed MNPs in the MOF support, as well as the improved adsorption of the reactant and desorption of the product due to the appropriate metal-support interaction and rich void space between core and shell.

The crystal structure of poly[(m4-4-bromoisophthalato-κ4O: O′:O′′:O′′′)zinc(II)], C8H3BrO4Zn

C8H3BrO4Zn, monoclinic, P21/c (no. 14), a = 4.7134(4) Å, b = 15.4354(13) Å, c = 12.0064(9) Å, β = 98.942(8)°, V = 862.89(12) Å3, Z = 4, Rgt(F) = 0.0445, wRref(F2) = 0.1193, T = 292.67(10) K.