Recent Progress on Engineering Highly Efficient Porous Semiconductor Photocatalysts Derived from Metal-Organic Frameworks

FeSe2 nanosheets as a bifunctional platform for synergistic tumor therapy reinforced by NIR-II light

Multi-functionality has been a constant pursuit in the development of next-generation drug carriers, as it will bring the potential for combination therapy by integrating diverse therapeutic modes. In this work, FeSe₂ nanosheets (NSs) have been prepared as a bifunctional platform to investigate their use in synergistic cancer therapy. Bifunctional FeSe₂ NSs exhibit exceptional Fenton-like activity that generates cytotoxic hydroxyl radical (˙OH) and strong broad photothermal performance including the second-infrared (NIR-II) spectral range, wherein the ˙OH production can be enhanced by NIR-II light irradiation. Furthermore, doxorubicin (DOX) was conjugated onto NSs via a pH-responsive hydrazone bond to achieve preferential drug release in an acidic microenvironment. Upon intratumoral administration, these bifunctional drug-carrying FeSe₂ NSs showed an NIR-II irradiation-reinforced strong tumor suppression effect, and no obvious toxicity to normal tissues was observed. This study provides a new paradigm for the design of advanced drug carriers relying on their inherent physicochemical properties.

Recent Advances in Metal-Organic Frameworks Derived Nanocomposites for Photocatalytic Applications in Energy and Environment

Solar energy is a key sustainable energy resource, and materials with optimal properties are essential for efficient solar energy-driven applications in photocatalysis. Metal-organic frameworks (MOFs) are excellent platforms to generate different nanocomposites comprising metals, oxides, chalcogenides, phosphides, or carbides embedded in porous carbon matrix. These MOF derived nanocomposites offer symbiosis of properties like high crystallinities, inherited morphologies, controllable dimensions, and tunable textural properties. Particularly, adjustable energy band positions achieved by in situ tailored self/external doping and controllable surface functionalities make these nanocomposites promising photocatalysts. Despite some progress in this field, fundamental questions remain to be addressed to further understand the relationship between the structures, properties, and photocatalytic performance of nanocomposites. In this review, different synthesis approaches including self-template and external-template methods to produce MOF derived nanocomposites with various dimensions (0D, 1D, 2D, or 3D), morphologies, chemical compositions, energy bandgaps, and surface functionalities are comprehensively summarized and analyzed. The state-of-the-art progress in the applications of MOF derived nanocomposites in photocatalytic water splitting for H2 generation, photodegradation of organic pollutants, and photocatalytic CO2 reduction are systemically reviewed. The relationships between the nanocomposite properties and their photocatalytic performance are highlighted, and the perspectives of MOF derived nanocomposites for photocatalytic applications are also discussed.

Design and Synthesis of Zinc-Activated Cox Ni2-x P/Graphene Anode for High-Performance Zinc Ion Storage Device

Zinc ion capacitors (ZICs) composed of capacitor-type cathodes and battery-type anodes have attracted widespread attention thanks to the huge potential in the next generation of low-cost energy-storage devices. It is a challenge to explore a universal anode for aqueous ZICs with high-efficiency energy-storage characteristics. In this work, the double-transition-metal composite Co_x Ni_2-x P/reduced graphene oxide (rGO) with sufficient electrochemical activity and charge-transfer kinetics was successfully synthesized. The Zn@CoNiP/rGO anode obtained by zinc-ion activation and a biomass-derived porous carbon cathode (PC) were assembled into an aqueous ZIC (CNP-ZIC) in 2 m ZnSO₄ . Finally, the CNP-ZIC reveals excellent energy and power densities with a working potential range of 0.2-1.9 V. CNP-ZICs shows high capacitance of up to 356.6 F g^-1 at 0.5 A g^-1 (based on the mass of active material on the PC cathode), which is far superior to the performance of conventional asymmetric energy storage devices (CoNiP/rGO//PC and Co₂ P/rGO//PC). The CNP-ZIC exhibits both a very high energy density of 143.14 Wh kg^-1 and good cycling life (∼92.2 % retention after 10000 charge-discharge cycles at 7.5 A g^-1 ). There is no doubt that this work provides a promising strategy for assembling novel zinc ion hybrid supercapacitors with high efficiency and stable output.

Catalysis based on ferroelectrics: controllable chemical reaction with boosted efficiency

Catalysts, which can accelerate chemical reactions, show promising potential to alleviate environmental pollution and the energy crisis. However, their wide application is severely limited by their low efficiency and poor selectivity due to the recombination of photogenerated electron-hole pairs, the back-reaction of interactants. Accordingly, ferroelectrics have emerged as promising catalysts to address these issues with the advantages of promoted light adsorption, boosted catalytic efficiency as a result of their intrinsic polarization, suppressed electron-hole pair recombination, and superior selectivity via the ferroelectric switch. This review summarizes the recent research progress of catalytic studies based on ferroelectric materials and highlights the controllability of catalytic activity by the ferroelectric switch. More importantly, we also comprehensively highlight the underlying working mechanism of ferroelectric-controlled catalysis to facilitate a deep understanding of this novel chemical reaction and guide future experiments. Finally, the perspectives of catalysis based on ferroelectrics and possible research opportunities are discussed. This review is expected to inspire wide research interests and push ferroelectric catalysis to practical applications.

Recent progress in electrochemical performance of binder-free anodes for potassium-ion batteries

Potassium ion batteries (PIBs) are regarded as one of the most promising candidates for large-scale stationary energy storage beyond lithium-ion batteries (LIBs), owing to the abundance of potassium resources and low cost. Unfortunately, the practical application of PIBs is severely restricted by their poor rate capacity and unsatisfactory cycle performance. In traditional electrodes, a binder usually plays an important role in integrating individual active materials with conductive additives. Nevertheless, binders are not only generally electrochemically inactive but also insulating, which is unfavorable for improving overall energy density and cycling stability. To this end, in terms of both improved electronic conductivity and electrochemical reaction reversibility, binder-free electrodes offer great potential for high-performance PIBs. Moreover, the anode is a crucial configuration to determine full cell electrochemical performance. Therefore, this review analyzes in detail the electrochemical properties of the different type binder-free anodes, including carbon-based substrates (graphene, carbon nanotubes, carbon nanofibers, and so on), MXene-based substrates and metal-based substrates (Cu and Ni). More importantly, the recent progress, critical issues, challenges, and perspectives in binder-free electrodes for PIBs are further discussed. This review will provide theoretical guidance for the synthesis of high-performance anode materials and promote the further development of PIBs.

Electrochemical Injection Oxygen Vacancies in Layered Ca2Mn3O8 for Boosting Zinc-Ion Storage

Manganese-based compounds have emerged as attractive cathode materials for zinc-ion batteries owing to their high operating voltage, large specific capacity, and no pollution. However, the structural collapse and sluggish kinetics of manganese-based compounds are major obstacles that hinder their practical applications. Here, a kind of novel layered Ca₂Mn₃O₈ with a low ion diffusion barrier and high structural stability has been achieved through an electrochemical charging process with in situ injecting oxygen vacancies. This greatly increases the electrochemical active area and improves the Zn ions diffusion coefficient by 2 orders of magnitude, which significantly enhances the reaction kinetics, pseudocapacitance properties, and capacity. As a result, the cathode containing oxygen vacancies present an impressive reversible capacity of 368 mAh g^-1, an unprecedented energy density of 512 Wh kg^-1, and superior capacity retention of 92.3% at a high current density of 5 A g^-1 after 3000 cycles. This work unveils an effective method for vacancy regulation of electrode materials, paving a new way to improve the electrochemical performance of zinc-ion batteries.

Nacre-inspired composite films with high mechanical strength constructed from MXenes and wood-inspired hydrothermal cellulose-based nanofibers for high performance flexible supercapacitors

Two dimensional MXenes with fascinating characteristics of high electrical conductivity, high density and electroactivity show promising applications in various fields. However, the direct applications of MXenes have been limited due to their inferior mechanical properties and easy restacking. Herein, a kind of nacre-like composite film constructed with Ti3C2Tx, cellulose nanofiber (HCNF) and sodium lignosulfonate (Lig) obtained through the hydrothermal process, named Ti3C2Tx/HCNF@Lig, has been successfully synthesized. The hydrothermal cellulose nanofiber (HCNF) film shows an enhanced mechanical strength (114 MPa) compared to that of the CNF film (95 MPa). Wood-inspired HCNF@Lig composite films present an enhanced mechanical tensile strength of up to 133 MPa. Nacre-like deformable Ti3C2Tx/HCNF@Lig(3@1) composite films exhibit high conductivity (up to 1.75 × 105 S m-1) and mechanical properties (up to 258 MPa). The electrodes of Ti3C2Tx/HCNF@Lig(3@1)97/3 composite film assembled flexible solid-state supercapacitors possess an excellent volumetric specific capacitance of 748.96 F cm-3. The corresponding deformable supercapacitors show an excellent energy density of 16.2 W h L-1 and outstanding electrochemical cycling stability. The as-prepared nacre-like Ti3C2Tx/HCNF@Lig composite films with high mechanical properties and electrochemical performance are expected to be practically applied in flexible/wearable energy storage devices.

Fish bone-derived interconnected carbon nanofibers for efficient and lightweight microwave absorption

In this work, we demonstrated a simple method for preparing three-dimensional interconnected carbon nanofibers (ICNF) derived from fish bone as an efficient and lightweight microwave absorber. The as-obtained ICNF exhibits excellent microwave absorption performance with a maximum reflection loss of –59.2 dB at the filler content of 15 wt%. In addition, the effective absorption bandwidth can reach 4.96 GHz at the thickness of 2 mm. The outstanding microwave absorption properties can be mainly ascribed to its well-defined interconnected nanofibers architecture and the doping of nitrogen atoms, which are also better than most of the reported carbon-based absorbents. This work paves an attractive way for the design and fabrication of highly efficient and lightweight electromagnetic wave absorbers.

Recent advances in the adsorptive remediation of wastewater using two-dimensional transition metal carbides (MXenes): a review

MXenes, since their discovery in 2011, have garnered significant research attention for a variety of applications due to their exciting physico-chemical properties.

Metal–organic framework derived carbon supported Cu–In nanoparticles for highly selective CO2 electroreduction to CO

The designed Cu–In bimetal exhibits much higher CO2-to-CO selectivity than monometallic Cu and In.

Cobalt-based metal–organic frameworks as functional materials for battery applications

Research progress on cobalt-based metal–organic frameworks as functional materials for battery applications has been presented.

A versatile approach for shape-controlled synthesis of ultrathin perovskite nanostructures

We demonstrate that ultrathin CsPbBr₃ nanostructures can be obtained by a simple mixing of precursor–ligand complexes under ambient conditions.

Incident-angle dependent operando XAS cell design: investigation of the electrochemical cells under operating conditions at various incidence angles

An operando characterization of electrode materials under electrochemical reaction conditions is important for their further development. X-ray absorption spectroscopy (XAS) presents a unique opportunity in this regard as the absence of a vacuum chamber in this technique makes it possible to collect spectroscopy data using user-designed operando cells. In the current study, the design and performance of an operando XAS cell are evaluated for characterizing solid oxide electrolysis cell working electrodes under a reaction environment that mimics high-temperature ammonia production conditions from H₂O and N₂. Sr₂FeMoO_6−xN_x (SFMON)-type double perovskite oxides were used as the cathode materials in these experiments. The operando cell contained a sample stage with a turnable head so that XAS data can be collected at different angles between the electrode and the X-ray beam with an accuracy of 0.5°. The mechanism to adjust the angle of incidence of the beam on the sample allows control over the depth of penetration of the X-ray photons into the electrode. At low angles, it becomes possible to collect surface sensitive data, which is of great importance as the electrochemical processes are believed to take place on the surface of the electrodes. Sr K-edge and Fe K-edge XAS collected at 2° and 45° angles showed that these the oxidation state changes occurring in these elements are different in the near-surface region compared to the bulk of the electrode. Such an ability to distinguish between the surface and bulk properties of the electrode during real reaction environment will help to understand the underlying phenomena better, which will enable electrode design targeted towards the reactions of interest.

Bias and time-dependent changes in the oxidation state and the atomic environment of the atoms of a working electrode occur on the gas/electrode interface.

An Efficient and Stable MoS2 /Zn0.5 Cd0.5 S Nanocatalyst for Photocatalytic Hydrogen Evolution

Photocatalytic hydrogen evolution by water splitting is highly important for the application of hydrogen energy and the replacement of fossil fuel by solar energy, which needs the development of efficient catalysts with long-term catalytic stability under light irradiation in aqueous solution. Herein, Zn_0.5 Cd_0.5 S solid solution was synthesized by a metal-organic framework-templated strategy and then loaded with MoS₂ by a hydrothermal method to fabricate a MoS₂ /Zn_0.5 Cd_0.5 S heterojunction for photocatalytic hydrogen evolution. The composition of MoS₂ /Zn_0.5 Cd_0.5 S was fine-tuned to obtain the optimized 5 wt % MoS₂ /Zn_0.5 Cd_0.5 S heterojunction, which showed a superior hydrogen evolution rate of 23.80 mmol h^-1  g^-1 and steady photocatalytic stability over 25 h. The photocatalytic performance is due to the appropriate composition and the formation of an intimate interface between MoS₂ and Zn_0.5 Cd_0.5 S, which endows the photocatalyst with high light-harvesting ability and effective separation of photogenerated carriers.

One-step hydrothermal synthesis of hierarchical nanosheet-assembled Bi2O2CO3 microflowers with a {001} dominant facet and their superior photocatalytic performance

Using citric acid (CA) and 1,5-naphthalenedisulfonic acid (NDSA) as the structure-directing agent, a hierarchical flower-like Bi₂O₂CO₃ product is successfully prepared via a simple one-step hydrothermal synthesis, which is spirally assembled by the {001} facet-dominated nanosheets. It is testified that the additive CA plays an important inducing role in forming the chemical composition of Bi₂O₂CO₃, the nanosized sheet-type subunits, and the exposure of the {001} facet, while the NDSA greatly improves the dispersity and porous structure of the Bi₂O₂CO₃ microflower. Due to the nano-size effect and distortion of surface Bi-O bonds, the Bi₂O₂CO₃ microflower could be excited by the visible light to exhibit a superior photocatalytic performance in the degradation of tetracycline (TC). Besides, it is found the exposed {001} facet of Bi₂O₂CO₃ would preferentially generate holes during the illumination process, thus enhancing the photooxidative activity of the Bi₂O₂CO₃ microflower. Finally, the structural and optical features of the Bi₂O₂CO₃ microflower have been discussed in detail, and its photocatalytic mechanism has also been proposed in this work.

Titania-based nanoheterostructured microspheres for prolonged visible-light-driven photocatalysis

Titanium dioxide is a widely used photocatalytic material possessing such advantages as safety, low cost, and high reactivity under the ultraviolet light illumination. However, its applicability in sunlight is limited due to the wide band gap and, as a consequence, the low quantum yield. Doping of titanium dioxide with metal or non-metal atoms and creating heterojunctions based on it are some of the most efficient ways to overcome this drawback. Herein we propose a new facile way of synthesis of nitrogen-doped TiO₂/MoO₃ and TiO₂/WO₃ microsphere-shaped nanocomposite photocatalysts, combining the advantages of these two methods. It is revealed that such structures are not only photo-active when exposed to visible light, but can also accumulate a photoinduced charge, thus allowing the catalytic reaction to be prolonged for a long time after the illumination is switched off (up to 48 h). With the help of EPR spectroscopy, paramagnetic defects in the samples were determined. The obtained results show good application prospects of the visible-light-driven TiO₂-based nanoheterostructured microspheres in the environmental purification.

Heterostructured g-CN/TiO2 Photocatalysts Prepared by Thermolysis of g-CN/MIL-125(Ti) Composites for Efficient Pollutant Degradation and Hydrogen Production

Photocatalysts composed of graphitic carbon nitride (g-CN) and TiO₂ were efficiently prepared by thermolysis of the MIL-125(Ti) metal organic framework deposited on g-CN. The heterojunction between the 12 nm-sized TiO₂ nanoparticles and g-CN was well established and the highest photocatalytic activity was observed for the g-CN/TiO₂ (3:1) material. The g-CN/TiO₂ (3:1) composite exhibits high visible light performances both for the degradation of pollutants like the Orange II dye or tetracycline but also for the production of hydrogen (hydrogen evolution rate (HER) up to 1330 μmolh⁻¹g⁻¹ and apparent quantum yield of 0.22% using NiS as a cocatalyst). The improved visible light performances originate from the high specific surface area of the photocatalyst (86 m²g⁻¹) and from the efficient charge carriers separation as demonstrated by photoluminescence, photocurrent measurements, and electrochemical impedance spectroscopy. The synthetic process developed in this work is based on the thermal decomposition of metal organic framework deposited on a graphitic material and holds huge promise for the preparation of porous heterostructured photocatalysts.

Two-Dimensional Materials and Composites as Potential Water Splitting Photocatalysts: A Review

Hydrogen production via water dissociation under exposure to sunlight has emanated as an environmentally friendly, highly productive and expedient process to overcome the energy production and consumption gap, while evading the challenges of fossil fuel depletion and ecological contamination. Various classes of materials are being explored as viable photocatalysts to achieve this purpose, among which, the two-dimensional materials have emerged as prominent candidates, having the intrinsic advantages of visible light sensitivity; structural and chemical tuneability; extensively exposed surface area; and flexibility to form composites and heterostructures. In an abridged manner, the common types of 2D photocatalysts, their position as potential contenders in photocatalytic processes, their derivatives and their modifications are described herein, as it all applies to achieving the coveted chemical and physical properties by fine-tuning the synthesis techniques, precursor ingredients and nano-structural alterations.

Atomic-scale synthesis of nanoporous gallium-zinc oxynitride-reduced graphene oxide photocatalyst with tailored carrier transport mechanism

Surface modified gallium-zinc oxynitride solid solution exhibited outstanding stability and visible-light activity for water splitting. However, the considerable rate of photo-induced charge recombination and the low surface area of the bulk photocatalyst limited its performance. Here, an efficient technique is proposed for the synthesis of a nanoporous oxynitride photocatalyst and its graphene-hybridized material. The nanoporous oxynitride photocatalyst was prepared via a nanoscale solid-state route, using microwave irradiation as an intermolecular-state activation method, Ga3+/Zn2+ layered double hydroxide as an atomic-level uniform mixed-metal precursor, and urea as a non-toxic ammonolysis soft-template. The graphene-hybridized photocatalyst was fabricated using a facile electrostatic self-assembly technique. The photocatalytic activity of the synthesized graphene hybridized nanoporous oxynitride photocatalyst was systematically improved through shortening the majority-carrier diffusion length and enhancing the density of active hydrogen evolution sites within the quasi-three-dimensional nanostructure, reaching 7.5-fold sacrificial photocatalytic hydrogen evolution, compared to the conventional 1 wt% Rh-loaded oxynitride photocatalyst.

Ultrathin 2D Metal-Organic Framework Nanosheets In situ Interpenetrated by Functional CNTs for Hybrid Energy Storage Device

The ultrathin nickel metal–organic framework (MOF) nanosheets in situ interpenetrated by functional carboxylated carbon nanotubes (C-CNTs) were successfully constructed. The incorporated C-CNTs effectively adjust the layer thickness of Ni-MOF nanosheets. The integrated hybrid MOF nanosheets delivered the boosted electrochemical performances and exhibited superior specific capacity of 680 C g−1 at 1 A g−1.

The controllable construction of two-dimensional (2D) metal–organic framework (MOF) nanosheets with favorable electrochemical performances is greatly challenging for energy storage. Here, we design an in situ induced growth strategy to construct the ultrathin carboxylated carbon nanotubes (C-CNTs) interpenetrated nickel MOF (Ni-MOF/C-CNTs) nanosheets. The deliberate thickness and specific surface area of novel 2D hybrid nanosheets can be effectively tuned via finely controlling C-CNTs involvement. Due to the unique microstructure, the integrated 2D hybrid nanosheets are endowed with plentiful electroactive sites to promote the electrochemical performances greatly. The prepared Ni-MOF/C-CNTs nanosheets exhibit superior specific capacity of 680 C g−1 at 1 A g−1 and good capacity retention. The assembled hybrid device demonstrated the maximum energy density of 44.4 Wh kg−1 at a power density of 440 W kg−1. Our novel strategy to construct ultrathin 2D MOF with unique properties can be extended to synthesize various MOF-based functional materials for diverse applications.

The chemistry of Ce-based metal-organic frameworks

Metal-organic frameworks (MOFs) have gained widespread attention due to their modular construction that allows the tuning of their properties. Within this vast class of compounds, metal carboxylates containing tri- and tetravalent metal ions have been in the focus of many studies due to their often high thermal and chemical stabilities. Cerium has a rich chemistry, which depends strongly on its oxidation state. Ce(iii) exhibits properties typically observed for rare earth elements, while Ce(iv) is mostly known for its oxidation behaviour. In MOF chemistry this is reflected in their unique optical and catalytic properties. The synthetic parameters for Ce(iii)- and Ce(iv)-MOFs also differ substantially and conditions must be chosen to prevent reduction of Ce(iv) for the formation of the latter. Ce(iii)-MOFs are usually reported in comprehensive studies together with those constructed with other RE elements and normally they are isostructural. They exhibit a greater structural diversity, which is reflected in the larger variety of inorganic building units. In contrast, the synthesis conditions of Ce(iv)-MOFs were only recently (2015) established. These lead selectively to hexanuclear Ce-O clusters that are well-known for Zr-MOFs and therefore very similar structural and isoreticluar chemistry is found. Hence Ce(iv)-MOFs exhibit often high porosity, while only a few porous Ce(iii)-MOFs have been described. Some of these show structural flexibility which makes them interesting for separation processes. For Ce(iv)-MOFs the redox properties are most relevant. Thus, they are intensively discussed for catalytic, photocatalytic and sensing applications. In this perspective, the synthesis, structural chemistry and properties of Ce-MOFs are summarized.

An in situ approach to functionalize metal–organic frameworks with tertiary aliphatic amino groups

Tertiary aliphatic amino modified UiO-67/66(Zr), IRMOF-n(Zn) and MIL-101(Fe) were synthesized by a facile and efficient one-pot strategy under the corresponding metal catalysis.

An Sc-based coordination polymer with concaved superstructures: preparation, formation mechanism, conversion, and their electrochemistry properties

Scandium-based coordination polymer octahedrons with concaved surfaces have been fabricated. The formation mechanism was also investigated. Sc₂O₃ octahedrons were obtained after simple calcination in a N₂ atmosphere.

Chemically grown bismuth-oxy-iodide (BiOI/Bi9I2) nanostructure for high performance battery-type supercapacitor electrodes

A dual phase bismuth oxyiodide (BiOI/Bi₉I₂) nanostructure battery type supercapacitor electrode is synthesized using chemical bath deposition (CBD) and the capacitance and energy/power density (ED/PD) reported.

Transition metal mixed oxide-embedded graphene oxide bilayers as an efficient electrocatalyst for optimizing hydrogen evolution reaction in alkaline media

A novel electrocatalyst containing different percentages of iron-titanium mixed oxide onto graphene oxide (GO) support was prepared by embedding via the thermal decomposition method (TD) and was coated on a Cu substrate through facile electroless Ni–Co–P plating.

Facile and Large-scale Synthesis of Defective Black TiO2−x(B) Nanosheets for Efficient Visible-light-driven Photocatalytic Hydrogen Evolution

In the work, we firstly report the facile and large-scale synthesis of defective black TiO2−x(B) nanosheets via a dual-zone NaBH4 reduction method. The structure, physico-chemical, and optical properties of TiO2−x(B) nanosheets were systematically characterized by powder X-ray diffraction, Raman spectroscopy, UV-Vis absorption spectroscopy, and X-ray photoelectron spectroscopy, etc. The concentration of Ti3+ can be well tuned by NaBH4 reduction. With increasing the mass ratio of NaBH4 to TiO2(B), the generation of Ti3+ defects gives rise to the increased intensity of a broad band absorption in the visible wavelength range. It is demonstrated that the TiO2−x(B) photocatalyst synthesized with the mass ratio of NaBH4 to TiO2(B) of 3:1 exhibited an optimum photocatalytic activity and excellent photostability for hydrogen evolution under visible-light irradiation. By combining the advantages of 2D TiO2(B) nanosheets architecture with those of Ti3+ self-doping and simultaneous production of oxygen vacancy sites, the enhanced photocatalytic performance of the defective TiO2−x(B) nanosheets was achieved.

Solvent-Free Synthetic Route for Cerium(IV) Metal-Organic Frameworks with UiO-66 Architecture and Their Photocatalytic Applications

A near solvent-free synthetic route for Ce-UiO-66 metal-organic frameworks (MOFs) is presented. The MOFs are obtained by energetically grinding the reagents, cerium ammonium nitrate (CAN) and the carboxylic linkers, in a mortar for a few minutes with the addition of a small amount of acetic acid (AcOH) as a modulator (8.75 equiv, 0.5 mL). The slurry is then transferred into a 2 mL vial and heated at 120 °C for 1 day. The MOFs have been characterized for their composition, crystallinity, and porosity and employed as heterogeneous catalysts for the photo-oxidation reaction of substituted benzylic alcohols to benzaldaldehydes under near-ultraviolet light irradiation. The catalytic performances, such as selectivity, conversion, and kinetics, exceed those of similar systems studied by chemical oxidation using similar Ce-MOFs as a catalyst. Moreover, the MOFs were found to be reusable up to three cycles without loss of activity. Density functional theory (DFT) calculations were used to fully describe the electronic structure of the best performing MOFs and to provide useful information on the catalytic activity experimentally observed.

Advances in Sn-Based Catalysts for Electrochemical CO2 Reduction

The increasing concentration of CO₂ in the atmosphere has led to the greenhouse effect, which greatly affects the climate and the ecological balance of nature. Therefore, converting CO₂ into renewable fuels via clean and economical chemical processes has become a great concern for scientists. Electrocatalytic CO₂ conversion is a prospective path toward carbon cycling. Among the different electrocatalysts, Sn-based electrocatalysts have been demonstrated as promising catalysts for CO₂ electroreduction, producing formate and CO, which are important industrial chemicals. In this review, various Sn-based electrocatalysts are comprehensively summarized in terms of synthesis, catalytic performance, and reaction mechanisms for CO₂ electroreduction. Finally, we concisely discuss the current challenges and opportunities of Sn-based electrocatalysts.

Enhanced polarization from flexible hierarchical MnO2 arrays on cotton cloth with excellent microwave absorption

To develop flexible microwave absorbers with strong attenuation capability has become a formidable challenge for applications of camouflage, stealth, and anti-electromagnetic pollution. Herein, a series of highly uniform cotton cloth@MnO₂ (CC@MnO₂) hierarchical structures with superior absorption performances were fabricated by simultaneously changing their intrinsic (α/δ phase) and extrinsic (2D/1D geometry) characteristics. The distinct absorption capability was dominantly contributed by the vertically grown dielectric MnO₂ 1D nanotube and conductive CC substrate, which could serve as a highly oriented backbone to ensure rapid electron transportation. Therefore, a well-designed CC@MnO₂ sample (α phase instead of the δ phase) exhibits the best absorption performance. The maximum reflection loss (RL) is -53.2 dB at 5.4 GHz and the effective bandwidth is 5.84 GHz for a thickness of only 2 mm. This unique structure exhibits polarization, conduction loss, and strong dissipation capability, which can be attributed to the high density of accumulated charges trapped at the interface, as confirmed by the electron holography analysis. Meanwhile, the MnO₂ coating does not affect the original flexibility of the CC and yields a massive interface and electronic conduction path. It is expected that CC@MnO₂ might shed a new light on the design of microwave absorbers.

Metal–organic framework-derived heterojunctions as nanocatalysts for photocatalytic hydrogen production

A summary of using the pore chemistry or surface chemistry of MOFs to construct heterojunction nanocatalysts for photocatalytic hydrogen production.