Search Results (652)

Lignin is one of the most abundant biopolymers in nature. The major challenge in lignin depolymerization lies in the formation of complex mixtures that require extensive downstream separation. Selective depolymerization strategies aim to overcome this limitation by promoting controlled bond cleavage while suppressing undesired secondary reactions. In this work, a series of rare-earth-free, perovskite-type mixed metal oxides with general compositions Zn_xNi_1–xTiO₃ and Cu_yNi_1–yTiO₃ were synthesized and evaluated as heterogeneous catalysts for the base-catalyzed depolymerization of lignin. Among the investigated materials, CuTiO₃ exhibited superior catalytic performance, enabling the formation of vanillin as the dominant monomer with high selectivity. The selected catalyst was further characterized using X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and Brunauer–Emmett–Teller (BET) surface area analysis. The combined effects of key reaction parameters, including temperature, pressure, lignin-to-catalyst ratio, NaOH concentration, and reaction time, were systematically investigated using response surface methodology (RSM). Under the optimized conditions (154 °C, 0.3 MPa, lignin-to-catalyst ratio of 24.5:1, 10 mL of 0.5 M NaOH, and 12 h reaction time), a monomer yield of 11.5 ± 0.46% with ~81% GC-selectivity toward vanillin was achieved. These findings demonstrate that perovskite-type titanates can serve as robust and reusable catalysts. Full article

The use of metal-free porous carbon catalysts can be considered one of the best alternatives for implementing a more sustainable fine chemical synthesis, as a challenge necessary to protect both our planet and society. It is recognized that the selection of the appropriate functional carbon catalyst, operating under the optimal reaction conditions, undoubtedly improves both the conversion and selectivity of a great variety of distinctive organic transformations, often through cascade reactions or even multicomponent synthesis. Increasing our knowledge of synthetic methodologies for metal-free carbon-based materials (including many of them on a large scale or even at an industrial scale), available characterization techniques, and computational methods represents an excellent opportunity to make these types of materials promising catalysts for a more sustainable future. In this context, this review is addressed to revisit the benefits and limitations of using each type of metal-free porous carbon catalyst in fine chemical synthesis, particularly in multi-bond forming processes for the synthesis of relevant heterocyclic systems. Full article

Photocatalytic water splitting for hydrogen (H₂) evolution is a critical sustainable energy strategy, and cadmium sulfide (CdS) is a promising visible-light photocatalyst due to its suitable band gap. However, the practical application of pure CdS is severely hindered by rapid charge-carrier recombination and significant photocorrosion. In this work, we constructed a CdS/vanadium carbide (VC) photocatalyst via a simple ultrasonic method. The structural, morphological, optical, and photoelectrochemical properties of the composites were systematically investigated. Under visible light (λ ≥ 420 nm) and with 0.35 M Na₂S-0.25 M Na₂SO₃ as the sacrificial agent, the optimized composite featuring a CdS:VC mass ratio of 10:1 (denoted CV-10) achieved a remarkable hydrogen evolution rate of 3485.6 μmol g⁻¹ h⁻¹. This rate represents a 60-fold enhancement over pure-phase CdS and significantly surpasses that of a conventional Pt/CdS catalyst. Furthermore, the CV-10 composite demonstrated excellent stability, showing no activity decay after 16 h of cycling. Spectroscopic and electrochemical analyses revealed that the metallic VC can function as an efficient cocatalyst, accelerating charge separation and transfer while suppressing electron–hole recombination. This work demonstrates that noble-metal-free VC is a highly effective and low-cost cocatalyst, providing a new pathway for designing efficient and stable CdS-based photocatalysts in solar hydrogen production. Full article

The rational configuration of electronic band structures through deep-seated structural disorder remains a formidable challenge in sustainable solar-to-fuel conversion. Herein, we report a transformative kinetic strategy to “freeze” an extraordinary density of non-equilibrium structural defects within an integrated Cu₄MgO₅/ZnO nanocomposite. Synthesized via a chitosan-assisted coordination-combustion route followed by rapid thermal quenching, the material preserves a record crystallographic dislocation density of 1.09 × 1015 m⁻² and significant lattice microstrain (1.04 × 10⁻³). This engineered structural disorder induces a profound reconfiguration of the electronic landscape, generating a continuous manifold of sub-bandgap “tail states” that narrow the optical bandgap to a remarkable 1.34 eV. Consequently, the defect-rich architecture facilitates unprecedented dual-channel photocatalytic performance under simulated solar irradiation in an aqueous solution containing 5 vol% triethanolamine (TEOA) as a sacrificial electron donor; the catalyst achieved a hydrogen evolution rate of 17,700.0 µmol g⁻¹ h⁻¹ and a methane production rate of 172.50 µmol g⁻¹ h⁻¹—representing a 36.3-fold and 43.1-fold enhancement over commercial ZnO, respectively. With an apparent quantum yield of 8.42% at 420 nm and robust photostability—maintaining 95.3% of its activity over five consecutive cycles (25 h total)—this noble-metal-free ternary system bypasses the limitations of traditional heterojunctions. Our findings establish a new benchmark for defect-engineered catalysts, providing a scalable blueprint for high-efficiency carbon neutrality and solar fuel production. Full article

p-nitrophenol (p-NP) is a pollutant with environmental persistence, bioaccumulation potential, and significant health risks, and is widely dispersed in wastewater, so efficient removal of p-NP is imperative. Among the various methods, the catalytic reduction of p-NP to p-aminophenol (p-AP) using sodium borohydride (NaBH₄) is a particularly promising one and, herein, catalysts play a crucial role. Among the various metals, Au shows unique catalytic activity for p-NP reduction. However, nanosized Au often exhibit limited activity and stability due to their high surface free energy. To address this challenge, we designed and synthesized Au-SnO_x hybrid nanoparticles confined within hollow mesoporous silica nanoreactors (Au-SnO_x@hm-SiO₂) via a soft-template-assisted co-adsorption strategy. The resulting bimetallic Au-SnO_x@hm-SiO₂ nanoreactor showed significantly enhanced catalytic activity toward the NaBH₄-mediated reduction of p-nitrophenol (p-NP) compared with its monometallic Au@hm-SiO₂ counterpart, owing to the synergistic effect between Au and SnO_x. Among various Au/Sn ratios, the catalyst with an Au/Sn molar ratio of 1:0.1 demonstrated the highest activity, achieving complete conversion of p-NP within 5 min at a p-NP/Au molar ratio of 529:1—a tenfold improvement over Au@hm-SiO₂. Moreover, the catalyst maintained high efficiency over six consecutive cycles, with only slight deactivation, benefiting from the protective silica shell. Full article

The lithium battery recycling industry is developing rapidly, and the rapid oxidation and degradation of dimethyl carbonate (DMC) in the wastewater generated by this industry is of crucial importance. In this study, Fe and Cu dopants were controlled and the C-SiO₂ framework with porous structures was constructed to synthesize FeCuC-SiO₂ and C-SiO₂ catalysts. The former could achieve 91.65% of DMC degradation within 60 min through peroxymonosulfate (PMS) activation, and the degradation rate was increased to 4.44 times compared to C-SiO₂ without Fe and Cu doping. And under optimized conditions, a DMC degradation rate of 90.57% can be achieved within 10 min by FeCuC-SiO₂. The catalyst has good stability and the catalytic activity can be maintained during reuse process for five times with over 70% of DMC degradation rate, 58.9% of mineralization rate, and a relatively low amount of metal leaching. Moreover, the degradation rate can still remain above 70% with the existence of impurity anions, demonstrating a strong salt resistance. Hydroxyl radicals (OH^•), sulfate radicals (SO₄^•−), and ¹O₂ were found to dominant the reaction in the FeCuC-SiO₂-PMS system, which were involved in both free radical and non-free radical pathways and led to excellent catalytic oxidation performance and environmental adaptability. In general, a novel design for a Fenton-like catalyst was presented, providing a theoretical basis for the improvement of oxidation efficiency and the regulation of reaction pathways in Fenton-like reactions. Full article

A novel transition-metal-free alkyne–thiol click polymerization with 100% atom economy is reported. Using ^tBuOLi as a catalyst at 80 °C, the polymerization efficiently yields poly(vinyl sulfide)s (PVSs) with molecular weights up to 11,800 g/mol and yields up to 91%. These sulfur-rich polymers exhibit high thermal stability (T_d up to 293 °C) and high refractive indices (1.8375–1.6383) across the visible range. By integrating abundant sulfur coordination sites with aggregation-induced emission (AIE) properties, the PVS aggregates serve as high-performance fluorescent chemosensors. The sensor enables exclusive, sensitive trace detection of Pd²⁺ and Au³⁺ with remarkable anti-interference capability and pH robustness (pH 1–7). Notably, an ultrafast response (1–2 min) for Pd²⁺ is achieved, with limits of detection (LOD) reaching 7.11 × 10⁻⁷ M for Pd²⁺ and 1.06 × 10⁻⁶ M for Au³⁺, and corresponding limits of quantification (LOQ) reaching 2.37 × 10⁻⁶ M and 3.53 × 10⁻⁶ M, respectively. This methodology offers a sustainable route to heteroatom-rich macromolecules for next-generation optical engineering and environmental monitoring. Full article

This study presents the production of isoamyl, n-butyl and cyclohexyl esters of levulinic acid with an excellent yield under solvent-free conditions. The catalysts used were MgAlO and M²⁺MgAlO-mixed oxides containing the transition metals (M²⁺ = Co²⁺, Ni²⁺, Zn²⁺), obtained from calcined layered double hydroxides (LDH). They are easily accessible, low-cost, and environmentally friendly and possess the requisite acid–base properties for esterification reactions. The effect of reaction time and the molar ratio of levulinic acid to the alcohols used on the esterification reaction was investigated. The catalysts were characterized by X-ray diffraction (XRD), XRF, SEM and temperature-programmed desorption of CO₂ (TPD-CO₂). Gas chromatography–mass spectroscopy (GC/MS) was used for the identification and quantification of the product mixtures. Mixed oxides containing transition metals exhibited significantly higher activity than MgAlO. Under the selected reaction conditions, the conversion of levulinic acid and the yield of isoamyl ester reached 100% at a reagent ratio of 1:1. As a by-product of esterification, only dicyclohexyl ether was found at a reactant ratio of 1:1.5. Full article

This study presents an approach for the “one-pot two-step” synthesis of 2,5-diformylfuran (DFF) from fructose using a metal-free phosphorus-doped carbon nitride (P-CN) catalyst. The bifunctional P-CN integrates P-O bonds for acid-catalyzed fructose dehydration to 5-hydroxymethylfurfural (HMF) and P-C/graphitic-N sites for selective aerobic HMF oxidation to DFF. The 10% P-CN catalyst achieved 91.5% DFF yield during the stepwise oxidation of isolated HMF under the mild conditions (1.5 MPa O₂, 120 °C), while the “one-pot” cascade reaction yielded 63% DFF due to competing side reactions. Characterization revealed that P-doping enhanced porosity (883 m²/g surface area) and electronic properties, with graphitic-N facilitating O₂ activation. P=O groups are hypothesized to mediate proton transfer from reactive substrates via hydrogen-bonding networks, thereby enhancing acid-catalyzed pathways. NH₃-TPD and XPS confirmed tailored acid sites and P-N/C elemental synergism, while FT-IR demonstrated substrate adsorption via P=O/HMF-OH interactions. The catalyst retained stability over multiple cycles, demonstrating its practicality. This work advances biomass valorization by elucidating the dual-role design of nonmetallic catalysts, offering an eco-friendly alternative to conventional metal-based systems. Full article

The fast growth of the aviation sector has intensified the need for sustainable alternatives to conventional fossil-based jet fuels. Sustainable aviation fuel (SAF) has emerged as one of the most promising strategies to reduce greenhouse gas emissions while remaining compatible with existing aviation infrastructure. Among the different feedstocks explored for SAF production, lipid-based resources such as vegetable oils, animal fats, and waste cooking oil have received considerable attention due to their high content of triglycerides and free fatty acids. Additionally, the increasing generation of plastic waste has stimulated interest in its catalytic valorization as an alternative carbon source for hydrocarbon fuel production. This mini-review summarizes recent advances in catalytic pathways for producing jet-fuel-range hydrocarbons (C₈–C₁₆) from lipid-based feedstocks and polyolefins. Particular emphasis is given on hydroprocessing reactions, including deoxygenation, cracking, and isomerization, which are essential to adjust fuel properties and meet aviation specifications. In this context, bifunctional heterogeneous catalysts play a crucial role, particularly regarding the influence of the metal phase and catalyst support on catalytic activity and stability. Different support classes, including metal oxides, mesoporous silicas, and zeolites, are discussed. Carbon-based materials, especially carbon nanotubes (CNT), are also highlighted due to their outstanding chemical and textural properties. Full article

The development of efficient catalysts for acetylene hydrochlorination is critical for replacing the industrially prevalent mercury chloride catalysts. Herein, a defective nitrogen-doped carbon material (NC-APT) is engineered via a facile co-polymerization of pyrrole, aniline, and thiophene, followed by a controlled calcination procedure. This co-polymerization strategy introduces abundant structural defects compared to mono-polymerization processes, primarily due to the lattice mismatch and steric hindrance between the distinct monomers, which disrupts the regularity of the polymer chain and prevents graphitic ordering. The resulting NC-APT catalyst features a high specific surface area of 375.7 m²·g⁻¹ and a substantial nitrogen dopant content of 14.4%, with 81% of the nitrogen existing as catalytically active edge structures (pyrrolic and pyridinic N). Consequently, the catalyst delivers exceptional performance, achieving 92% acetylene conversion at 220 °C with a C₂H₂ gas hourly space velocity (GHSV) of 80 h⁻¹. This performance significantly outperforms many reported metal-free counterparts and rivals that of traditional metal-based catalysts. This work offers new insights into the rational design of carbon-based, metal-free catalysts through monomer mismatch engineering. Full article

Self-sustained metal aerogels are emerging as advanced porous materials with a 3D network of nanostructures that are exclusively made of metals. Metal aerogels possess a distinctive combination of metallic nanoparticles with excellent electronic conductivity, and the excellent porosity of the aerogels allows the extensive exposure of electrocatalytic active sites, together with remarkable mass transport networks in a single entity, unlocking widespread application potential ranging from energy storage and conversion to environmental remediation. In this review, we systematically examine the potential of metal aerogels as electrocatalysts for ethanol electro-oxidation. Various synthesis routes, structure–property relationships, and their function as anode electrocatalysts have been critically reviewed. Due to their 3D porous metallic nature, noble metal aerogel catalysts were found to exhibit excellent ethanol oxidation currents, anti-poisoning for reaction intermediates, high mass, and specific activities of 5–20 times those of traditional Pd/C catalysts. In conclusion, it is shown that metal aerogel catalysts exhibit enhanced activity for ethanol electro-oxidation currents over traditional Pd/C catalysts. Despite this, several challenges exist in realizing the commercial applications of metal aerogels, which have been clearly and elaborately stated as future perspectives and research directions in the field of metal aerogel electrocatalysis. Full article

Ammonia decomposition represents a promising route for CO₂-free hydrogen production; however, the development of efficient and stable catalysts remains a critical challenge. In this work, a series of Al-based mixed-oxide catalysts (AlM, where M = Ni, Co, Ce) were synthesized via co-precipitation and systematically investigated to elucidate the relationship between physicochemical properties and catalytic performance in ammonia decomposition. Comprehensive characterization by X-ray diffraction (XRD), N₂ physisorption (BET), scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM–EDX), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), and pyridine-adsorbed Fourier transform infrared spectroscopy (FTIR-Py) revealed significant variations in surface area, morphology, dispersion, and acidity as a function of the incorporated metal. Among the investigated catalysts, the AlNi system exhibited superior activity, achieving the highest ammonia conversion over the studied temperature range. This enhanced performance is attributed to its high specific surface area, homogeneous mesoporous structure, and a balanced distribution of Lewis/Brønsted acid sites, which promote effective ammonia adsorption, activation and decomposition. Kinetic analysis further confirmed the favorable reaction pathway on AlNi, as evidenced by its lower apparent activation energy and higher pre-exponential factor compared to the other materials. The results demonstrate a clear correlation between surface acidity, textural properties, and catalytic performance, highlighting the pivotal role of AlM interactions in governing ammonia decomposition. These findings provide valuable insights for the rational design of efficient catalysts for hydrogen production from ammonia. Full article

Electrocatalytic water splitting powered by renewable energy is a promising route for sustainable hydrogen production. Rather than developing separate catalysts for HER and OER, recent efforts focus on multifunctional electrocatalysts that can efficiently drive both reactions, simplifying system design and improving efficiency. A major limitation of conventional water splitting is the high overpotential and low-value oxygen production in OER. To overcome this, hybrid water splitting replaces OER with more valuable oxidation reactions, such as pollutant degradation or organic upgrading, enhancing overall energy and economic efficiency. This review covers the fundamentals of water splitting and highlights key physicochemical techniques for probing electrocatalyst activity, particularly structural reconstruction under operating conditions. It evaluates noble-metal, nonprecious-metal, and metal-free nanocarbon catalysts in both acidic and alkaline media, with emphasis on their roles in alternative anodic reactions. Finally, it outlines current challenges and future directions for developing efficient, durable, and sustainable electrocatalysts for advanced hydrogen production systems. Full article

To overcome the inherent drawbacks of poly(propylene carbonate) (PPC), such as poor thermal stability, low mechanical strength, and high surface energy, this study introduced, for the first time, 1,1,1-trifluoro-2,3-epoxypropane (TF-PO) as a third monomer into the metal-free TEB/PPNCl catalytic system for the terpolymerization with carbon dioxide (CO₂) and propylene oxide (PO), successfully synthesizing a series of fluorinated PPC (PPCF). The optimal polymerization conditions ($60 °C$, 2.0 MPa, 12 h, n(PO):n(TF-PO) = 100:4) were determined through systematic optimization. Comprehensive structural characterization (FT-IR, NMR, XPS) confirmed the successful incorporation of TF-PO into the polymer backbone. Property evaluation revealed that the PPCF materials exhibited substantial improvements in thermal stability, mechanical strength, hydrophobicity, and dielectric properties compared to unmodified PPC. The optimal sample, PPCF4, achieved a $5\%$ weight-loss temperature ($T_{d,-5\%}$) of $242 °C$, a glass transition temperature ($T_{\mathrm{g}}$) of $42 °C$, a tensile strength of 21.5 MPa, and a Young modulus of 296 MPa. With a $5\%$ TF-PO feed ratio, the material’s water contact angle increased to 102°, and its dielectric constant reached 6.01 at ${10}^4$ Hz. Furthermore, density functional theory (DFT) calculations elucidated the Lewis acidity of the TEB catalyst and the reactive sites of the monomers, leading to a proposed mechanism for the ternary alternating copolymerization. This work provides an effective synthetic strategy and theoretical foundation for preparing high-performance and functionalized PPC materials through molecular structure design. Full article