Search Results (241)

N-heterocyclic carbenes (NHCs) have demonstrated their versatility as catalysts for new activations and synthetic transformations of aldehydes. NHCs were originally applied in benzoin condensation and the Stetter reaction, while the development of new protocols under oxidative conditions has further expanded the potential of this methodology for the formation of carbon−carbon and carbon−heteroatom bonds. Among these reactions, NHCs are recognized as promising organocatalysts for the aerobic oxidation of aldehydes to carboxylic acids. However, to our knowledge, a comparison with other metal-free protocols has never been conducted. This review is intended to provide a perspective on aldehyde oxidation into the corresponding carboxylic acid catalyzed by NHCs, from its first practical description in 2009 until the beginning of 2025, and to compare it with other metal-free methods. Full article

This study presents the development of a novel Cu–Co–O-codoped graphitic carbon nitride (g-C₃N₄) catalyst for efficient peroxymonosulfate (PMS) activation to degrade sulfamethoxazole (SMX) in aqueous environments. The synthesized Cu–Co–O-g-C₃N₄ catalyst demonstrated exceptional catalytic performance, achieving 90% SMX removal within 10 min—significantly outperforming pristine g-C₃N₄ (14%) and O-doped g-C₃N₄ (22%)—with a reaction rate constant of 0.63 min⁻¹. The superior activity was attributed to the synergistic effects of Cu-Co bimetallic doping and oxygen incorporation, which enhanced the active sites, stabilized metal ions, and minimized leaching. Mechanistic studies revealed a dual-pathway degradation process: (1) a radical pathway dominated by sulfate radicals (SO₄•⁻) and (2) a non-radical pathway driven by singlet oxygen (¹O₂), with the latter identified as the dominant species through quenching experiments. The catalyst exhibited broad pH adaptability and optimal performance at neutral to alkaline conditions. Characterization techniques (XRD, FTIR, XPS) confirmed successful doping and revealed that oxygen incorporation modified the electronic structure of g-C₃N₄, improving charge carrier separation. This work provides a sustainable strategy for antibiotic removal, addressing key challenges in advanced oxidation processes (AOPs), and highlights the potential of multi-heteroatom-doped carbon nitride catalysts for water purification. Full article

The growing global demand for energy necessitates the efficient utilization of unconventional petroleum resources, particularly heavy oil reserves. However, extracting, transporting, and processing these resources remain challenging due to their low mobility, low API gravity, and significant concentrations of resins, asphaltenes, heteroatoms, and metals. In recent years, various in situ upgrading techniques have been explored to enhance heavy oil quality, with catalytic aquathermolysis emerging as a promising approach. The effectiveness of this process largely depends on the development of cost-effective, environmentally friendly catalysts. This study investigates the upgrading performance of water-soluble ammonium alum, (NH₄)Al(SO₄)₂·12H₂O, for an extra-heavy oil sample from the Zarafshan Depression, located along the Tajikistan–Uzbekistan border. Comprehensive analyses demonstrate that the catalyst facilitates the breakdown of heavy oil components, particularly resins and asphaltenes, into lighter fractions. As a result, oil viscosity was significantly reduced by 94%, while sulfur content decreased from 896 ppm to 312 ppm. Furthermore, thermogravimetric (TG-DTG) analysis, coupled with Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and X-ray diffraction (XRD), revealed that the thermal decomposition of ammonium alum produces catalytically active Al₂O₃ nanoparticles. These findings suggest that ammonium alum is a highly effective water-soluble pre-catalyst for hydrothermal upgrading, offering a viable and sustainable solution for the development of extra-heavy oil fields. Full article

Amidst global imperatives for sustainable energy and environmental remediation, carbon aerogels (CAs) present a transformative alternative to conventional carbon materials (e.g., activated carbon, carbon fibers), overcoming limitations of disordered pore structures, unmodifiable surface chemistry, and functional inflexibility. This review systematically examines CA-based electrochemical systems as its primary focus, analyzing fundamental charge-storage mechanisms and establishing structure–property–application relationships critical to energy storage performance. We critically assess synthesis methodologies, emphasizing how stage-specific parameters govern structural/functional traits, and detail multifunctional modification strategies (e.g., heteroatom doping, composite engineering) that enhance electrochemical behavior through pore architecture optimization, surface chemistry tuning, and charge-transfer kinetics acceleration. Electrochemical applications are extensively explored, including the following: 1. Energy storage: supercapacitors (dual EDLC/pseudocapacitive mechanisms) and battery hybrids. 2. Electrocatalysis: HER, OER, ORR, and CO₂ reduction reaction (CO₂RR). 3. Electrochemical processing: capacitive deionization (CDI) and electrosorption. Beyond this core scope, we briefly acknowledge CA versatility in ancillary domains: environmental remediation (heavy metal removal, oil/water separation), flame retardancy, microwave absorption, and CO₂ capture. Full article

The development of cost-effective and scalable air/oxygen electrode materials is crucial for the advancement of Zn–air batteries (ZABs). Porous carbon materials doped with heteroatoms have attracted considerable attention in energy and environmental fields because of their tunable nanoporosity and high electrical conductivity. In this work, we report the synthesis of a three-dimensional (3D) N and P co-doped porous carbon (PA@pDC-1000), derived from a conjugated polyaniline–phytic acid polymer. The cross-linked, rigid conjugated polymeric framework plays a crucial role in maintaining the integrity of micro- and mesoporous structures and promoting graphitization during carbonization. As a result, the material exhibits a hierarchical pore structure, a high specific surface area (1045 m² g⁻¹), and a large pore volume (1.02 cm³ g⁻¹). The 3D N, P co-doped PA@pDC-1000 catalyst delivers a half-wave potential of 0.80 V (vs. RHE) and demonstrates a higher current density compared to commercial Pt/C. A primary ZAB utilizing this material achieves an open-circuit voltage of 1.51 V and a peak power density of 217 mW cm⁻². This metal-free, self-templating presents a scalable route for the generating and producing of high-performance oxygen reduction reaction catalysts for ZABs. Full article

The increasing demand for efficient and sustainable energy conversion technologies has driven extensive research into alternative electrocatalysts for the oxygen reduction reaction (ORR). Platinum-based catalysts, while highly efficient, suffer from high costs, scarcity, and long-term instability Laser-Induced Graphene (LIG) has recently attracted considerable interest as an effective metal-free electrocatalyst for oxygen reduction reaction (ORR), owing to its remarkable electrical conductivity, customizable surface functionalities, and multi-scale porous architecture. This review explores the synthesis strategies, physicochemical properties, and ORR catalytic performance of LIG. Additionally, this review offered a detailed overview regarding the effective pole of heteroatom doping (N, S, P, B) and functionalization techniques to enhance catalytic activity. Finally, we highlight the current challenges and future perspectives of LIG-based ORR catalysts for fuel cells and other electrochemical energy applications. Furthermore, laser-induced-graphene (LIG) has emerged as a highly attractive candidate for electrochemical energy conversion systems, due to its large specific surface area, tunable porosity, excellent electrical conductivity, and cost-effective fabrication process. This review discusses recent advancements in LIG synthesis, its structural and electrochemical properties, and its applications in supercapacitors, batteries, fuel cells, and electrocatalysis. Despite its advantages, challenges such as mechanical stability, electrochemical degradation, and large-scale production remain key areas for improvement. Additionally, this review explores future perspectives on optimizing LIG for next-generation energy storage and conversion technologies. Full article

With the continuous consumption of fossil energy and the related environmental problems, clean energy, especially the hydrogen energy-derived water electrolysis, has attracted wide attention. However, as a result of the high energy consumption of water electrolysis and the limitations of single-function catalysts, there is an urgent need for cheap and simple-to-make bifunctional catalysts. In this work, based on the NiFe-LDH that is usually used for OER (Oxygen Evolution Reaction), doping of heteroatoms was carried out and a bifunctional catalyst could be then prepared using biomass as the carbon source. The preparation of catalyst precursors and in situ reduction were performed through the coupling process of hydrothermal and pyrolysis to enhance the electrolytic activity of the catalyst. Results showed that the overpotentials required to reach a current density of 10 mA·cm⁻² for the HER and OER processes were 305.2 mV and 310.4 mV, respectively, which are superior to the commercial catalysts. In the subsequent characterization, the structural characteristics of the catalyst support and their structure–activity correlation with active metals were systematically investigated by TEM, XRD, and XPS analysis, providing mechanistic insights into the catalytic behavior. The basic catalytic mechanisms of HER and OER were also obtained: the HER process was due to the formation of a Ni₃Fe alloy structure during catalyst preparation, which changed the electronic structure of the catalyst, while the OER process was induced by the formation of a NiOOH intermediate. The research results are expected to provide new ideas and data support for the preparation of bifunctional catalysts. Full article

The electrochemical reduction of nitrate to ammonia offers a promising solution for both alleviating nitrate pollution in wastewater and providing a sustainable ammonia source for agriculture use. This review focuses on the role of carbon-based catalysts in electrochemical nitrate reduction to ammonia, emphasizing their potential in addressing environmental pollution and supporting sustainable ammonia production. Carbon materials, known for their abundance, affordability, and eco-friendly properties, are central to this process. The review highlights key strategies for enhancing catalytic performance, including heteroatom doping, the development of porous structures, and the integration of metal/metal oxide nanoparticles. Additionally, it addresses significant challenges such as weak nitrate adsorption, slow reaction kinetics, and competition with the hydrogen evolution reaction. Through the integration of advanced material design, mechanistic insights, and innovative engineering strategies, this review provides valuable guidance for the future design of carbon-based catalysts, paving the way for significant advancements in both nitrate removal and sustainable ammonia synthesis. Full article

Aromatic volatile organic compounds (VOCs) pose significant environmental and public health risks due to their toxicity, carcinogenicity, and role as precursors of hazardous secondary pollutants. Zeolite-based metal catalysts, with their well-defined microporous structures, tunable acidity, and high thermal stability, have shown promise in the catalytic oxidation of aromatic VOCs. However, the influence of the zeolite microenvironment on supported metal active sites remains insufficiently understood, limiting the rational design of advanced catalysts. This review highlights how microenvironmental parameters—including pore architecture, acid site distribution, framework composition, and surface/interface engineering—can be modulated to enhance adsorption, oxygen activation, and metal–support interactions. Advances in hierarchical porosity, heteroatom substitution, and surface hydrophobicity are discussed. This review provides a framework for the development of next-generation zeolite-based catalysts and offers strategic guidance for advancing microenvironment-controlled catalysis in sustainable environmental remediation. Full article

This paper investigated the kinetics involved in the adsorption of methylene blue (MB) on activated carbon. Tests of the adsorbent (granulometric composition and FT-IR analyses) showed that it contains a wide range of particle sizes (5–250 μm) and that the most frequent vibrations are caused by N=C=N stretching, C=C=C stretching, metal–oxygen vibrations (e.g., Fe-O), and heteroatomic vibrations (C-Cl or C-Br). Increasing the dose of adsorbent and decreasing the initial concentration of methylene blue increases the efficiency of adsorption, while the most intensive adsorption takes up to 10 min. The adsorption process follows pseudo-second-order kinetics, which indicates that adsorption occurs due to chemical interactions between the adsorbate and adsorbent. The results indicate that the use of activated carbon achieves a high level of MB removal, especially under optimized conditions. Full article

Biochar-based materials have gathered increasing attention as sustainable catalysts for carbon dioxide (CO₂) valorization, offering a green alternative to traditional metal-based systems. Produced from renewable biomass through pyrolysis, biochar possesses key features—such as high surface area, rich porosity and tunable surface chemistry—that make it particularly suited for heterogeneous catalysis. This review highlights recent advances in the use of biochar-derived catalysts for key CO₂ conversion reactions, focusing on cycloaddition to epoxides, dry reforming of methane and catalytic biomass upgrading. Emphasis is given to the role of biochar’s origin and preparation methods, which critically influence its structure, surface functionality and catalytic performance. Feedstocks rich in mineral content or oxygenated groups, for instance, can enhance CO₂ activation and product selectivity. Furthermore, tailored modifications—such as doping with heteroatoms or supporting metal nanoparticles—further boost catalytic activity and stability by tuning acid–base behavior, while maintaining low toxicity and cost-effectiveness. Compared to conventional catalysts, biochar-based systems offer advantages in low cost, recyclability and resistance to deactivation. Challenges remain in standardizing production methods, controlling structural variability, minimizing metal leaching and scaling up. This review presents biochar as a versatile, renewable platform for CO₂ utilization, highlighting the importance of rational design, feedstock selection and functionalization strategies for developing efficient, sustainable catalytic systems, in line with green chemistry and circular economy principles. Full article

Chiral ansa-η⁵-complexes of transition metals have shown remarkable efficacy in organometallic synthesis and catalysis. Additionally, enantiomerically pure ansa-complexes hold promise for the development of novel chiral materials and pharmaceuticals. The discovery and synthesis of a diverse range of group IVB and IIIB metal complexes represents a significant milestone in the advancement of stereoselective catalytic methods for constructing metal-C, C-C, C-H, and C-heteroatom bonds. The synthesis of enantiomerically pure metallocenes can be accomplished through several strategies: utilizing optically active precursors of η⁵-ligands, separation of diastereomers of complexes with enantiomerically pure agents, and synthesis via the stereocontrolled reactions of enantiomerically pure σ-complexes with prochiral anions of η⁵-ligands. This review focuses on the analysis of various nuances of the synthesis of enantiomerically pure ansa-η⁵-complexes of titanium and lanthanum families. Their applicability as effective catalysts in asymmetric carbomagnesiation, carbo- and cycloalumination, oligo- and polymerization, Diels–Alder cycloaddition, reactions of zirconaaziridines, cyclization, hydrosilylation, hydrogenation, hydroamination, and other processes are highlighted as well. Full article

Sludge-derived biochar (SDB) synthesized by the pyrolysis of sludge is gaining enormous interest as a sustainable solution to wastewater treatment and sludge disposal. Despite the proliferation of general biochar reviews, a focused synthesis on SDB-specific advances, particularly covering the recent surge in multifunctional wastewater treatment applications (2020–2025), receives little emphasis. In particular, a critical analysis of recent trends, application challenges, and future research directions for SDB is still limited. Unlike broader biochar reviews, this mini-review highlights the comparative advantages and limitations of SDB, identifies emerging integration strategies (e.g., bio-electrochemical systems, catalytic membranes), and outlines future research priorities toward enhancing the durability and environmental safety of SDB applications. Specifically, this review summarized the advances from 2020 to 2025, focusing exclusively on functional modifications, and practical applications of SDB across diverse wastewater treatment technologies involved in adsorption, catalytic oxidation, membrane integration, electrochemical processes and bio-treatment systems. Quantitative comparisons of adsorption capacities (e.g., >99% Cd2+ removal, >150 mg/g tetracycline adsorption) and catalytic degradation efficiencies are provided to illustrate recent improvements. The potential of SDB in evaluating traditional and emerging contaminant degradation among the Fenton-like, persulfate, and peracetic acid activation systems was emphasized. Integration with membrane technologies reduces fouling, while electrochemical applications, including microbial fuel cells, yield higher power densities. To improve the functionality of SDB-based systems in targeting contamination removal, modification strategies, i.e., thermal activation, heteroatom doping (N, S, P), and metal loading, played crucial roles. Emerging trends highlight hybrid systems and persistent free radicals for non-radical pathways. Despite progress, critical challenges persist in scalability, long-term stability, lifecycle assessments, and scale-up implementation. The targeted synthesis of this review offers valuable insights to guide the development and practical deployment of SDB in sustainable wastewater management. Full article

The exacerbation of the global energy crisis has brought the development of efficient and sustainable hydrogen energy to the forefront of contemporary research endeavors. Molybdenum disulfide (MoS₂), recognized for its outstanding electrocatalytic performance as a two-dimensional material, has attracted significant interest for its potential in the hydrogen evolution reaction (HER). This review delves into the heteroatom-doped modification strategy centered on MoS₂ and its effectiveness in enhancing electrocatalytic hydrogen evolution. The influence of various doping elements (including noble metals, transition metals, and non-metals) on the electronic structure and catalytic efficiency of MoS₂ is also analyzed, elucidating the mechanism by which heteroatom doping enhances the catalytic performance and stability of MoS₂. Looking ahead, the integration of multiple doping elements, utilization of advanced computational techniques, and advancement of novel synthetic methods position MoS₂ for practical applications in the field of hydrogen energy, driving the progress and improvement of sustainable energy initiatives. Full article

Metalloporphyrins, owing to their structural resemblance to natural enzyme active sites and highly tunable coordination environments, have emerged as promising catalysts for converting CO₂ into value-added chemicals and fuels. Considerable efforts have been made to modify metalloporphyrins to improve their catalytic capability for CO₂ reduction. One approach involves modifying the metal coordination environment (known as the first coordination sphere) to generate heteroatom-containing metalloporphyrins, particularly N-confused and O/S-substituted variants. While heteroatom-containing metalloporphyrins were first synthesized in 1989, their use in CO₂ reduction catalysis was not reported until after 2020. Herein, we review the recent progress in the design, catalytic performance, and mechanistic studies of N-confused and O/S-substituted metalloporphyrins towards CO₂ reduction. This review encompasses both experimental and theoretical computational work, as well as the use of porphyrins as catalysts in photocatalysis and electrocatalysis. Finally, based on the current research advances, we present critical recommendations and future research directions, with a focus on theoretical studies, in the hope of facilitating the rational design of novel catalysts for sustainable energy conversion and environmental remediation. Full article