The dual imperatives of carbon-neutral chemical manufacturing and advanced wastewater remediation require high-performance electrocatalysts capable of orchestrating complex, multi-electron reactions. However, pristine catalyst lattices are fundamentally bottlenecked by linear scaling relations. This critical review establishes defect engineering as the definitive strategy for bypassing these thermodynamic limitations, offering a unified mechanistic framework that bridges sustainable energy conversion and environmental remediation. Moving beyond empirical material catalogues, this work systematically interrogates how localized structural imperfections—vacancies, dopants, and synergistic interfaces—act as precision atomic-scale electronic regulators. By modulating the transition-metal d-band center and triggering spatial charge redistribution, defects successfully decouple intermediate binding energies to steer reaction pathways thermodynamically. A comprehensive analysis elucidates the electronic origins of defect-mediated performance across green ammonia synthesis (nitrogen and nitrate reduction) and advanced wastewater treatment (electro-Fenton, targeted non-radical persulfate activation, and priority pollutant electroreduction). Furthermore, this review challenges the pervasive assumption of static active sites, emphasizing how operando interrogation reveals the highly dynamic, transient nature of defect architectures under applied electrochemical bias. Finally, the frontier of artificial intelligence-guided discovery and multi-defect synergy is highlighted, charting a translational roadmap from atomic-level precision to robust industrial reactor integration. Ultimately, this review elevates defect electrocatalysis from a purely descriptive phenomenon into a predictive, quantitatively guided design discipline essential for achieving closed-loop global sustainability.
Renewable electricity-driven water electrolysis offers a promising route to low-emission hydrogen, yet exceptional laboratory catalyst performance does not necessarily translate into efficient, durable, and scalable electrolyzer operation. This review examines nanostructured electrocatalysts across interconnected length scales, linking atomic-level electronic structure and adsorption energetics with the potential dependent active phase, electrode transport processes, and complete device integration. Noble metal catalysts, nickel–molybdenum systems, molybdenum disulfide, nickel–iron oxyhydroxides, reconstructing precatalysts, atomically dispersed sites, and compositionally complex materials are critically assessed according to the evidence needed to identify active sites and validate long-term stability. Particular attention is given to alkaline water electrolysis, proton-exchange membrane water electrolysis, anion-exchange membrane water electrolysis, oxygen ion solid oxide electrolysis, and proton-conducting ceramic electrolysis. The review shows that apparent activity can be overstated by surface roughness, transient reconstruction, electrolyte purity, or low catalyst loading, while practical deployment is limited by catalyst layer uniformity, membrane compatibility, ion transport, water supply, gas removal, dissolution, thermal management, dynamic loading, and manufacturing constraints. A unified translation framework is proposed to distinguish mechanistic promise from device-relevant progress and guide the development of efficient, durable, resource-conscious, and verifiably low-emission hydrogen production at scale.
The efficient and simultaneously selective conversion of methane to methanol has been one of the most research-intensive topics in catalysis over the past decades. The weaker C-H bond of methanol promotes the production of over-oxidized species. The present computational study examines the catalytic performance of organometallic complexes with electron rich Earth abundant metals (cobalt, nickel, copper, formally negatively charged). A deliberately designed ligand is proposed to secure the negative charge on the metal and enable the formation of stable terminal metal-oxygen bonds. The ligand coordinates the metal with metal-carbon bonds, and the skeleton of the ligand is chosen to constrain the motion of the coordinated carbon atoms, avoiding the insertion of oxygen to the metal-carbon bond. We found that the energy barriers for methane activation are less than 15 kcal/mol across all three metals, and that the turnover frequency is determined by the methanol-release step, which is highly temperature-sensitive. Therefore, solvent effects and temperature can be tuned to improve the overall catalytic efficiency. The most impressive result of our study is that the activation barriers for methane and methanol are competitive (within 1–2 kcal/mol). This observation makes catalysts with electron rich metal centers unique and promising for efficient and selective conversion of methane to methanol.
The escalating demand for sustainable energy sources and chemical feedstocks has intensified research efforts toward the catalytic conversion of lignocellulosic biomass into value-added products. This comprehensive review critically examines recent advances in metal-based catalytic systems for biomass valorization, encompassing noble metals, transition metals, and their alloys. We systematically analyze the fundamental mechanisms governing catalytic transformations of cellulose, hemicellulose, and lignin, with particular emphasis on structure-activity relationships and catalyst design principles. The review addresses critical challenges including catalyst deactivation, selectivity control, and scalability, while highlighting emerging opportunities in single-atom catalysis, bimetallic synergies, and integrated biorefinery concepts. Furthermore, we discuss the role of advanced characterization techniques and computational approaches in accelerating catalyst discovery. This work provides a roadmap for future research directions aimed at achieving economically viable and environmentally sustainable biomass conversion technologies.
We describe a sequence-guided approach to identify and engineer key amino acids in orthologous CYP4B1 enzymes for selective ω-hydroxylation of saturated fatty acids and sequential hydroxylation of trans-stilbene to trans-4,4′- and trans-4,3′-dihydroxystilbene. Orthologous enzymes generally share high sequence identities and catalyze the same reactions, but often exhibit subtle yet distinct activity and selectivity profiles. Understanding the sequence determinants that underlie this observation is not only essential for elucidation of evolutionary adaptations, but can also be used for rational biocatalyst design. Within this study, sequence comparison of a set of orthologous CYP4B1 enzymes identified four amino acids as key activity and selectivity drivers for catalysis. These were systematically engineered by introducing potentially beneficial single amino acid exchanges into less active/selective CYP4B1 orthologs, and vice versa. The exchanges shifted activity and selectivity trends for ω-hydroxylation of lauric acid by the mutated orthologs in a manner consistent with those observed for the corresponding wildtype enzymes across multiple orthologous backgrounds. Notably, combinatorial mutagenesis of two amino acids resulted not only in additive, but also in orthologous- and substrate-dependent adverse influences on activity and selectivity, which likely reflects the enzyme function optimized by nature in the context of the individual orthologs evolutionary background. For conversion of trans-stilbene, two beneficial amino acid exchanges between two CYP4B1 orthologs resulted in 95% conversion of trans-stilbene and 85% dihydroxystilbenes. In summary, we demonstrate that systematic introduction of only one or two sequence-guided mutations can be sufficient to substantially alter activity and selectivity profiles of orthologous enzymes for a given substrate, which highlights the usefulness of this approach for rational design of biocatalysts.
We investigate CO methanation over nickel-decorated strontium hydroxyapatite (NiSH) nanorods based catalysts by varying Ni loadings, prepared by the impregnation method. The catalytic experiments were conducted at light-off temperatures ranging from 225°C to 400 °C, under ambient pressure. The key properties of prepared catalysts were characterized by XRD, N2 physisorption, TEM, SEM, TPR and H2-TPD and H2-chemisorption. The basicity of the catalysts was measured by CO2-TPD analysis. A 10NiSH catalyst is optimal for CO methanation, with over 90% CH4 selectivity at 300 °C and 0.1 MPa, with complete CO conversion. The synergistic interaction between highly dispersed Ni species and the basic Sr-modified hydroxyapatite support significantly enhances catalytic activity and CH4 selectivity. Unlike conventional Ni-supported catalysts, the present 10NiSH system provides improved Ni dispersion, optimized reducibility, enhanced CO adsorption/activation, and superior hydrogenation ability, resulting in high yield of CH4 at relatively low temperature. In-situ DRIFT spectroscopy evidenced reaction intermediates, and a reaction mechanism is proposed. The basicity of SH role is CO2 adsorption in conjunction with Ni metal in hydrogenation activity are key roles. The optimal loading exhibited better properties in terms of Ni particle size, narrowly distributed histograms, and better reducibility. Based on the catalyst performance results, overall, the 10NiSH is the most active and selective catalyst due to its high Ni dispersion.
Esters are highly relevant industrial compounds. They can be produced via biocatalysis in accordance with the Green Chemistry Principles using immobilized lipases, a highly specific catalyst for esterification that operates under mild reaction conditions. However, the adoption of biocatalysis for ester production is mainly hindered by the high cost of immobilized lipases relative to the selling prices of most alkyl esters. Moreover, most studies of enzymatic ester synthesis in the literature focus only on reaction conversion, dedicating less attention to process metrics and the techno-economic drawbacks of biocatalytic processes. This study presents a process metrics – oriented evaluation of enzymatic alkyl ester synthesis catalyzed by immobilized lipases, aiming to support more rational and economically relevant process development. Solvent-free syntheses of ethyl and octyl esters (acetate, caprate, and oleate) were carried out using immobilized Candida antarctica lipase B (Novozym 435). Mid- and long-chain esters showed higher conversions and superior process metrics compared to short-chain systems, mainly due to reduced inhibition and more favorable reaction media. Although excess alcohol improved conversion in some cases, it often reduced product concentration and volumetric productivity, highlighting the importance of jointly evaluating metrics such as space-time yield, catalytic productivity, and added-value index. n-Octyl acetate synthesis was selected for process design, simulation, and preliminary techno-economic assessment, revealing that despite high conversion and improved catalytic productivity via biocatalyst reuse, the process remains economically unfeasible due to the high contribution of enzyme cost to operational expenditures. The integration of process metrics with reaction engineering and techno-economic analysis provides a robust framework for bridging the gap between laboratory optimization and industrial implementation of biocatalytic processes.
IntroductionGreen synthesis of nanomaterials using plant extracts has gained significant interest. This method replaces toxic reducing and capping agents with natural sources such as plant extracts, microorganisms, algae, fungi, or biomolecules. In this study, copper-based nanomaterials were synthesized using aqueous extracts from various parts of Moringa oleifera, including leaves, seeds, and stem bark.MethodsThe synthesized copper oxide materials were characterized using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The prepared materials were then tested for their antimicrobial, antioxidant, and Eriochrome Black-T (EBT) degradation activities.Results and DiscussionStructural characterization via XRD revealed the successful formation of a mixed phase of crystalline cuprous oxide and copper (Cu2O/Cu) along with amorphous copper oxide materials. FT-IR analysis confirms that compounds such as polyphenols, alkaloids, flavonoids, terpenoids, and reducing sugars significantly contribute to the synthesis of these copper oxide nanomaterials, supporting their formation. SEM and TEM analysis confirmed the formation of nanomaterials. Additionally, the study measured the concentrations of total phenols, flavonoids, and tannins in various parts of Moringa oleifera to better understand their influence on copper oxide synthesis. Notably, an amorphous copper oxide material derived from Moringa oleifera leaf extract exhibited higher antimicrobial and antioxidant activities and achieved 40% EBT degradation, while the crystalline material showed lower activity. The study discusses these results in detail, correlating the activity with the characterization studies.
Methanogenesis is an anaerobic, energy-conserving metabolism that converts CO2, acetate, and methylated compounds to methane, constituting a key terminal step in the mineralization of organic matter in many oxygen-limited ecosystems. In the modern biosphere, biological methane formation is overwhelmingly dominated by methanogenic archaea. Despite its phylogenetic constraint, this metabolism exerts disproportionate influence on global carbon cycling, radiative forcing, and methane-based energy systems. The defining biochemical signature of methanogenesis is methyl-coenzyme M reductase (MCR), a nickel tetrapyrrole enzyme that catalyzes the final methane-forming step through Ni-F430 chemistry. This cofactor chemistry enables selective C-H bond formation and cleavage under aqueous, physiologically compatible conditions. It can also function in the reverse direction in anaerobic methane-oxidizing archaea. This review examines archaeal methanogenesis as a case study in how biochemical constraint and evolutionary diversification jointly shape a single catalytic solution across multiple physiological contexts. We summarize the major routes of methane formation and the bioenergetic architectures that support them. We then evaluate competing scenarios for methanogenesis evolution in light of comparative genomics, geochemical constraints, and the rapidly expanding catalogue of methane-cycling archaea, emphasizing an evolutionary history marked by modular assembly, differential loss, and horizontal transfer rather than a simple pattern of vertical inheritance. Mechanistic sections focus on MCR and related alkyl-coenzyme M reductases, highlighting structural features, cofactor variation, post-translational modification repertoires, and recent advances that illuminate critical steps in Ni-F430 biosynthesis and ATP-dependent activation of the Ni(I) catalytic state. Finally, we discuss implications for biotechnology and catalysis, including selective methane abatement by mechanism-guided inhibition, strategies to enhance anaerobic digestion and biological biogas upgrading, and the use of MCR family enzymes as experimentally tractable platforms for selective anaerobic hydrocarbon transformations and bioinspired catalyst development.
DNA topoisomerase-IA is an essential enzyme that relaxes supercoiled DNA by introducing transient single-strand breaks through a covalent phosphorylated tyrosine (PTR) intermediate. This cleavage occurs when the active-site tyrosine of dTopo-IA forms a covalent bond with the DNA phosphate backbone, resulting in PTR formation. Although dTopo-IA is believed to mediate strand passage via an enzyme-induced DNA gate, the actual opening of this gate has not been demonstrated experimentally or theoretically. To address this gap, we employed 200-nanosecond (ns) molecular dynamics (MD) simulations using AMBER18 to explore the catalytic mechanism and conformational dynamics of dTopo-IA. Important parameters like RMSD, RMSF, the number of hydrogen bonds, hydrogen bond distances, the radius of gyration (RoG), binding free energy, solvent-accessible surface area (SASA), and per-residue pair-wise decomposition energy were analyzed. Our simulations revealed that the bond between PTR and nucleotide acts as a gatekeeper, regulating the opening and closing of the DNA gate critical for strand passage. MD trajectories clearly demonstrate that gate opening and strand passage occur only after the formation of the covalent bond between PTR and the C5′ atom of the DNA strand. Additionally, we investigated how topoisomerase selectively binds single-stranded DNA in the presence of double-stranded DNA to initiate its catalytic function. The enzymatic roles of residues Gln-223, Arg-533, and Lys-117 were also elucidated in the process. This provides a novel and deeper understanding of the enzyme’s mechanism, which has been challenging to capture through experimental techniques alone, and potentially aids the development of targeted anticancer therapies by disrupting DNA replication in cancer cells.
IntroductionWater pollution, stemming from various sources such as pharmaceuticals waste, pesticides, herbicides, textile dyes, resins, and phenolic compounds, is a significant concern in today’s world. Even small amounts of water pollutants can have detrimental effects on human health and ecosystems. Therefore, proper treatment of industrials wastewater through sewage treatment plants is essential for effective wastewater management.MethodIn this study, undoped TiO2 and silver-doped TiO2 nanoparticles were synthesized via Sol-Gel method and thoroughly characterized using X-Ray Diffraction (XRD), UV-Visible Spectroscopy, Scanning Electron Microscopy (SEM), Energy Dispersive X-rays (EDX), and Fourier Transform Infrared Spectroscopy (FT-IR).ResultsResults revealed a red shift in the UV-Visible spectrum, with increasing silver percentage (2%–4% weight), and silver doping effectively tuned the band gap from undoped TiO2 from 3.03 eV to 2.47. XRD analysis revealed an average crystallite size range of 8–12 nm. SEM studies demonstrated morphological changes due to doping, while EDX confirmed the elemental composition of the nanoparticles. FT-IR analysis affirmed sample purity and vibrations of the required functional groups.DiscussionThe synthesized nanoparticles exhibited efficient degradation of Malachite Green and Rose Bengal dyes under varied conditions, with 2% weight TiO2 displaying the highest Photodegradation Efficiency (PDE) of 98% for Malachite Green at optimal conditions of 4 mg catalyst concentration, 85 μM dye concentration, and pH 9 and 2 mg catalyst concentration, 10 μM dye concentration, and pH 3 for Rose Bengal. Kinetic analysis revealed pseudo first order kinetics with observed rate constant of 0.9438 min-1 for Malachite Green and 0.18118 min-1 for Rose Bengal, supporting the efficiency of heterogeneous photocatalysis for wastewater treatment. This study underscores the significance of the optimizing degradation parameter for practical applications.
IntroductionDevelopment of a mild and sustainable protocol for the carbon-carbon bond formation via Knoevenagel condensation is essentially desirable because the products, aryledene derivatives, are useful intermediates and are widely used in the manufacture of fine chemicals, pharmaceutically active molecules, calcium channel blockers, natural products, as well as in the production of flavours and fragrances.MethodActivated carbon sheets were fabricated from pomegranate peels via calcination, activation by KOH and were characterization using Raman spectroscopy, powder XRD, FESEM, FESEM-EDX, and TGA studies. The ionic liquid, [pmIm]Br was synthesized by reacting a 1:1 mixture of N-methyl imidazole and n-pentyl bromide under microwave irradiation.Results and discussionPomegranate peel–derived two-dimensional graphitic activated carbon (PPAC) nanosheets, with lateral dimensions of 40–200 nm and lengths of 4–10 μm, were confirmed through Raman spectroscopy, powder XRD, FESEM, and other studies. The PPAC, combined with the ionic liquid [pmIm]Br, demonstrated remarkable catalytic performance in the Knoevenagel condensation of aromatic aldehydes with active methylene compounds, producing the corresponding aryledene derivatives in excellent yields (90%–95%) within 5–20 minutes under mild conditions. Furthermore, the PPAC/[pmIm]Br catalytic system efficiently facilitated the synthesis of xanthene derivatives via a tandem condensation–cyclization pathway. The catalyst was easily recovered and reused over five consecutive cycles with minimal loss of activity. This work highlights a renewable, biomass-derived carbon framework as a dual-function, environmentally friendly catalyst for effective C–C bond formation and heterocycle synthesis, offering a scalable approach aligned with green chemistry and waste valorization principles.
Diffusion of hydrolytic enzymes into biomass particles is a potential limiting step, which has yet to be studied in detail separate from intrinsic hydrolysis kinetics. We developed and applied a pore-enzyme diffusion model for both adsorbing and non-adsorbing enzymes and coupled them to reactor-level mass balance equations. With this multi-scale model, the effects of biomass particle porosity, size, and adsorption capacity on the characteristic time of enzyme diffusion and adsorption were predicted over an expected range of these parameters. Using a hydrolysis limiting threshold characteristic time for enzyme diffusion of 6 hours, this model mapped the transport parameter space between two distinct zones: diffusion limiting and non-diffusion limiting. The model also predicted a decrease in characteristic time with an increase in the biomass-to-enzyme loading ratio. At the particle level, characteristic time was most strongly affected by firstly adsorption capacity, then particle radius, adsorption affinity, and porosity.
This dry fungus-reinforced nanoparticle synthesis is the first proficient plan of action to replace the use of hazardous chemical, physical, and other bio-methods. Here, we report the synthesis of gold bio-nanocomposites (GBNCs) via immobilization of dry biomass prepared with conventional and lyophilization methods. Under atmospheric conditions, dried Aspergillus trinidadensis VM ST01′ OL587588 functions as a reducing and capping agent in water without any solvent or buffer interference. The use of dried biomass provides additional benefits for the synthesis of GBNCs, such as short synthesis time (24 h; 36 h with wet biomass) without incubation, better shelf life (more than 18 months), improved catalytic activity, intact morphology, etc. The generated GBNCs were characterized by various analytical techniques and were found to have a roughly spherical shape with a mono-dispersed diameter of approximately 25 nm, as determined with high-resolution transmission electron microscopy. The influence of stirring and biomass concentration on the kinetics was also studied for the GBNC fabrication process. Optimized stoichiometric results have shown 3.5 × 1015 gold atoms per milligram of dried biomass prepared by both methods. The crystalline nature and surface charge of GBNCs were analyzed by powder X-ray diffraction and zeta potential studies, respectively. FT-IR studies have shown the participation of various biomass functional groups in forming GBNCs. The surface morphology of GBNCs was investigated by scanning electron microscopy. A comparative thermal stability of dried biomass and GBNCs was evaluated by thermo-gravimetric analysis, with a large difference in residual mass. Here, GBNCs have been shown to be a truly potent heterogeneous catalyst for the reduction of nitrobenzene in water using sodium borohydride with yields up to 95% isolation. The industrial suitability of GBNCs has been established with their broad operational pH (4–10) and temperature (25 °C–80 °C) ranges, reusability (more than 10 cycles), storage stability (more than 18 months), and successful scale-up investigations (up to 5 gm).
This Perspective reflects on practices that lead to the development of high turnover cross-coupling catalytic cycles involving palladium. These processes are attractive for the manufacture of agrochemical, human or veterinary active ingredients, and in some respects are more sustainable than alternatives that use base metals at much higher loadings. The practices are structured in terms of important elements of the workflow for developing a cross-coupling for commercialization, and are discussed using the key metrics that drive catalytic efficiency and sustainability. Realistic opportunities and challenges for metal recovery and reuse are also among the messages discussed.
Electrochemical CO2 reduction represents a promising approach for mitigating carbon emissions while generating value-added fuels and chemicals. While catalyst design mainly dictates activity and product selectivity, system-level performance is strongly influenced by the interplay between electrolyzer configuration and operating parameters. In this study, a zero-gap membrane electrode assembly electrolyzer incorporating a cation exchange membrane is systematically investigated under practical considerations. The applicable operating window is successfully extended to elevated temperatures and pressures, demonstrating robust practicality and efficient conversion. Comprehensive evaluation of cell voltage, Faradaic efficiency, and energy efficiency reveals that a balanced combination of catalyst loading, electrolyte concentration, and flow rate enables high CO selectivity (>90%) and energy efficiency exceeding 40% at moderate current density (100 mA/cm2). By integrating multiple operational parameters, this work advances the application of cation exchange membrane based CO2 electrolysis and offers practical insights for bridging laboratory research and scalable implementation.
This study presents the synthesis and characterization of AgxFe2-xO3 nanoparticles as highly efficient photocatalysts and excellent antimicrobial agents. AgxFe2-xO3 nanoparticle synthesis was carried out through the sol–gel auto-combustion method. It was extensively characterized using X-ray diffraction (XRD), which confirmed the formation of crystalline α-Fe2O3 nanoparticles with a crystallite size of 22.23 nm. Ag-doped Fe2O3 has an average crystallite size of 23.08 nm. Fourier transform infrared (FTIR) spectroscopy provided insights about metal oxide bond formation and constant force for octahedral and tetrahedral sites, which suggest the location of the cation and anion. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed rhombohedral Ag-doped Fe2O3 nanomaterials with a uniform particle size around 20–50 nm, which matches the XRD results. UV–vis spectroscopy shows absorption shifting toward visible light for the AgxFe2-xO3 compared to pristine Fe2O3, indicating the utilization of the maximum light spectrum for efficient light harvesting in the visible region. AgxFe2-xO3 exhibited excellent stability and reusability for visible-light-driven photocatalytic dye degradation with a rate constant of 1.27 × 10−2 min−1, which is two-fold more than that of the pristine Fe2O3 (0.51 × 10−2 min−1). AgxFe2-xO3 was also found to be more efficient in inhibiting the growth of Proteus mirabilis with a 16 mm zone of inhibition.
In the past 20 years, unspecific peroxygenases (UPOs) have emerged as promising biocatalysts for various organic transformations. Particularly, we have witnessed great attention being paid to the screening of new enzymes and expansion of the substrates/products. However, challenges such as enzyme stability, low turnover numbers, and substrate specificity hinder their widespread utilization in practical organic synthesis. This review article provides a concrete and mini-overview of the challenges associated with using UPOs in organic synthesis and discusses strategies for enzyme engineering to overcome these limitations. The article highlights recent advancements in UPO research and presents potential solutions to enhance their catalytic efficiency, stability, substrate specificity, and regioselectivity. Additionally, the review outlines the current methodologies employed for directed evolution and protein engineering of UPOs, along with computational modeling approaches for rational enzyme design. By addressing the challenges and exploring avenues for enzyme engineering, this review aims to shed light on the prospects of UPOs in organic synthesis.
