Search Results (693)

Cellulose is the most promising abundant renewable polymer material with the highest potential for the future low-carbon biorefineries. However, its utilization in industry is limited by the structural recalcitrance as a result of organization of crystalline domains, fibrillar architecture hierarchy and intramolecular and intermolecular hydrogen bonding which is responsible for access restriction for the catalysts and consequent cleavage of the glycosidic bonds. Therefore, efficient depolymerization of cellulose is of paramount importance as a step in biomass conversion into the low molecular products. In this review, the recent advances in cellulose depolymerization are discussed. The chemical, enzymatic, thermal, thermochemical, mechanochemical, oxidative and hybrid catalytic method is thoroughly discussed. Attention is paid to the mechanism of the depolymerization reaction steps as glycosidic bond activation as hydrolytic, radical mediated, and energy assisted pathways. Selectivity and conversion efficiency based on substrate morphology, solvent system and catalyst design are also discussed. Further, there is a comparison of key performance metrics which are relevant for the industrial process as product yield, carbon efficiency, energy demand, stability of the catalyst, solvent recyclability and impact to the environmental lifecycle. The pros and cons of the various methods are also represented. Processes based on mineral acids enable rapid conversion. However, they suffer from corrosion, waste handling issues and degradation by-products. On the other hand, enzymatic depolymerization processes offer relatively high selectivity but they are limited in terms of feedstock sensitivity and slow reaction kinetics. The downstream valorization mechanisms are also described with the result being that no single available technology is capable of satisfying all industrial requirements. Thus, future progress expects integrated circular processes where advanced catalysis, process intensification and digital optimization strategies take place. Full article

We report the synthesis, characterisation and electronic modulation of three novel fused polyheterocyclic ligands—naphtho[1,2-b]furan-4,5-dione (1), furo[3′,2′:3,4]naphtho[1,2-d]imidazole (2), and benzo[a]furo[2,3-c]phenazine (3)—and their Cu(II), Zn(II) and Fe(II/III) complexes. Compound (1) was isolated at 96.5% yield using fulvic acid as a green organocatalyst. ⁵⁷Fe Mössbauer spectroscopy identified two high-spin Fe(III) environments in a 37:63 ratio (δ = 0.377 mm s⁻¹; Δ = 0.62 and 1.01 mm s⁻¹), with no evidence of magnetically ordered oxide phases. Six enantiomeric metal malate salts were synthesised at 86–93% yield for spectrophotometric titrations. The key finding is a striking Cu(II)-specific enantioselective molecular recognition: (3) binds (S)-(−)-malate Cu(II) with log K = 9.02, a factor of 2.5× higher than the (R)-(+)-malate complex (log K = 8.62), while Fe(II) and Zn(II) show no enantioselectivity. These results establish chiral counter-ion engineering combined with π-conjugated polyheterocyclic scaffolds as a powerful strategy for chiroptical sensing and asymmetric catalysis. Full article

To address the urgent demand for eco-friendly and low-cost catalysts to replace toxic heavy-metal additives in energetic materials, this work focuses on developing biomass-derived copper-doped porous carbon (CuPC) as a high-efficiency catalyst for the thermal decomposition and combustion of molecular perovskite energetic material (H₂dabco)NH₄(ClO₄)₃(DAP-4). Biomass carbonaceous material has garnered extensive attention in many fields, owing to the low cost, high utilization efficiency, and environment protection. Herein, the CuPC catalysts were rationally designed and fabricated via the high-temperature carbonization treatment of biomass carbonaceous material precursor. The catalytic effects of CuPC on the thermal decomposition and combustion characteristics of DAP-4 were systematically investigated. The results revealed that CuPC possessed inherent catalysis property on the decomposition and combustion reaction of DAP-4. Cu_xO_y nanoparticles were uniformly distributed on the surface of carbonized biomass substrates, endowing the catalysts with superior dispersibility. Thermal analysis results indicated that the addition of 5 wt% CuPC-3 reduced the thermal decomposition peak temperature from 378 °C of raw DAP-4 to 350 °C of DAP-4/CuPC-3. Moreover, the apparent activation energy of DAP-4 was notably decreased with the incorporation of CuPC catalysts. The combustion characterization results demonstrated that DAP-4 exhibited a more intense combustion process with the addition of CuPC, accompanied by elevated maximum combustion temperature and enhanced combustion heat. The catalytic mechanism of CuPC on the thermal decomposition and combustion of DAP-4 was further proposed. This work provides a targeted strategy for designing sustainable biomass-based catalysts to optimize the energy release performance of advanced molecular perovskite energetic materials. Full article

Topologically chiral molecular knots and links represent a unique class of stereochemical architectures in which handedness is encoded by the global crossing pattern of an entangled framework rather than by a local stereogenic element. Their configurational robustness and shape-persistent chiral environments make them promising platforms for molecular recognition, catalysis, chiroptical response, and spin-selective transport. This review summarizes recent progress in the stereoselective synthesis of topologically chiral knots and links, with emphasis on chirality transfer from point, axial and helical elements into persistent topological handedness. Major synthetic strategies are organized into helicity-driven approaches, template-free dynamic systems, coordination-driven self-assembly, and chiral self-sorting. The applications of knots in host–guest confinement, asymmetric catalysis, chiral recognition, and spin-selective transport are also discussed. Full article

Ferroptosis, an iron-dependent and lipid peroxidation-driven form of regulated cell death, has emerged as a “versatile player” in oncology. It exerts a dual, context-dependent role in cancer, acting as both a potent tumor suppressor and a facilitator of tumor progression and therapeutic resistance. This review systematically delineates the core molecular regulatory networks of ferroptosis, highlighting the intricate balance between its execution mechanisms—driven by polyunsaturated fatty acid (PUFA) oxidation, iron catalysis, and mitochondrial dysfunction—and the robust endogenous defense systems, including the GSH-GPX4, FSP1/DHODH-CoQ10, and GCH1-BH4 axes. We deeply explore the dichotomous nature of ferroptosis in tumorigenesis: while classical tumor suppressors like p53 and CDKN2A harness ferroptosis to halt tumor growth, cancer cells can hijack lipid metabolic reprogramming and specific enzymes (e.g., iPLA2β) to evade cell death and promote distant metastasis. Furthermore, we dissect the multidimensional crosstalk between ferroptosis and the tumor microenvironment (TME), emphasizing its bidirectional immunoregulatory effects. Although CD8+ T cell-derived IFN-γ can sensitize tumor cells to ferroptosis and amplify anti-tumor immunity, aberrant ferroptotic activation can paradoxically foster an immunosuppressive niche. Finally, we summarize the latest translational strategies using small-molecule inducers and synergistic combination therapies, emphasizing that biomarker-guided patient stratification remains the ultimate paradigm for overcoming resistance and realizing precision ferroptosis-targeted cancer therapy. Full article

Poly(trimethylene ether) glycol (PO3G), a bio-based polyether polyol with excellent flexibility and superior hydrolytic stability, has emerged as a critical raw material for the preparation of high-performance polymer materials. This work optimized the sulfuric acid-catalyzed polymerization process and assessed the feasibility of using p-toluenesulfonic acid (PTSA) as an alternative catalyst. A parametric study was conducted to establish a reliable operating window for the sulfuric acid system. DFT calculations demonstrated that the driving force for chain growth decreases with increasing chain length, that recombination between chains of significantly different lengths is more favorable than between chains of equal length, and that the formation of disulfate esters is thermodynamically more favorable. Although PTSA required a higher catalyst loading, the resulting polymer had a markedly lower yellowness index. Prolonged reaction times lead to a molecular weight plateau, especially at high PTSA concentrations, while the yellowness index continues to increase after reaching the plateau. ¹H NMR analysis indicated the formation of benzenesulfonate monoester intermediates during PTSA catalysis, suggesting a potentially milder pathway and possibly fewer side reactions compared to the sulfuric acid system. This paper provides theoretical and experimental foundations for the green, efficient synthesis of PO3G and the catalyst optimization for analogous bio-based polyether polyols. Full article

This review summarizes recent applications of nuclear magnetic resonance (NMR) in olefin polymerization catalysis. Due to its capability for quantitative characterization of molecular structures and in situ study, NMR is employed to study the structure of catalysts, and to trace catalyst/cocatalyst interactions, the evolution of active species, monomer insertion, and chain-end formation. This review emphasizes the activation mechanisms of molecular catalysts, ion-pair structures, and the measurement of kinetics. It also discusses the potential applications of in situ multinuclear NMR and isotope labeling technologies in olefin polymerization catalysis studies. Full article

Inspired by natural porphyrin-containing enzymatic active sites, metalloporphyrins have become important platforms for oxygen reduction reaction (ORR) catalysis because of their well-defined structures and tunable coordination environments. Recently, breaking the N₄-coordination environment of cobalt porphyrins by inverting one pyrrolic unit to generate N₃C₁-site, i.e., N-confused porphyrin, has emerged as an effective strategy to promote their electro-catalyzing ORR capability. Herein, we reviewed recent progress in N-confused cobalt porphyrin in catalyzing ORR, with special emphasis on the influence of the catalyst’s architecture. We first summarized the general ORR mechanism on metalloporphyrins and the computational methods commonly used for mechanistic studies. Then, for comparison, the more common modification strategies like meso- and β-position substitution, axial coordination, and dinuclear design were reviewed for cobalt porphyrin-based catalysts. The main part reviewed the N-confused cobalt porphyrins with three different architectures, i.e., molecular, framework, and supported heterogeneous molecular form, highlighting their synthesis, characterization, electrocatalytic ORR behavior, and mechanistic interpretation from both experimental and theoretical perspectives. It summarizes the current understanding of why CoN₃C₁ systems outperform the original CoN₄ porphyrin systems. The architecture of catalysts was found to affect the selectivity and mechanisms of ORR, along with the discussion of pH. The effects of N-confused strategy were compared to other modification strategies. Finally, we proposed possible directions for integrated catalyst design and mechanism studies. Full article

A comprehensive thermodynamic and molecular-level investigation of adsorption on MgY and NH₄Y zeolites is presented using inverse gas chromatography at infinite dilution (IGC-ID), combined with a Hamaker-based formalism and an extended five-parameter Lewis acid–base model. The study introduces a unified framework that integrates dispersive, polar, and donor–acceptor interactions while explicitly accounting for temperature-dependent intermolecular geometry. The results demonstrate that the London dispersive free energy exhibits a highly linear temperature dependence (R² > 0.999), while the corresponding surface energy decreases linearly with temperature (e.g., ${\gamma }_s^d\left(T\right)=-0.297T+189.48$ mJ·m⁻² for MgY), reflecting the progressive weakening of dispersion forces. Simultaneously, the intermolecular separation distance follows a linear relation $r\left(T\right)=r_0+{\alpha }_{\mathrm{eff}}T$, with ${\alpha }_{\mathrm{eff}}$ values on the order of (2–3) × 10⁻³ Å·K⁻¹ for MgY, enabling the determination of intrinsic contact distances $r_0$ at 0 K, varying between 4.00 Å and 6.60 Å. A major finding is that the molecular surface area of adsorbed probes is not constant but follows a quadratic temperature dependence with excellent accuracy (R² > 0.999), establishing adsorption cross-section as a thermodynamic variable. The comparison between MgY and NH₄Y reveals two distinct adsorption regimes: MgY exhibits a structured and strongly dispersive interaction field associated with Mg²⁺ cations, whereas NH₄Y displays enhanced polarity, stronger specific interactions, and greater molecular flexibility driven by hydrogen bonding and protonic effects. Thermodynamic analysis of Lewis acid–base interactions shows that classical linear models are insufficient. Statistical evaluation (R² ≈ 0.986, minimum AIC/BIC, lowest RMSE) demonstrates that the five-parameter Hamieh model provides the most accurate and physically meaningful description, capturing nonlinear donor–acceptor interactions and amphoteric coupling effects. Overall, this work establishes a novel thermodynamic methodology that quantitatively links macroscopic surface energetics to microscopic interaction parameters, providing new insight into adsorption mechanisms and a robust framework for the rational design of porous materials in catalysis, separation, and energy applications. Full article

Surface-enhanced Raman spectroscopy (SERS) has evolved from a fundamental optical phenomenon to a powerful, molecule-specific analytical technique capable of detecting ultra-trace-level species across biomedicine, catalysis, environmental monitoring, and national security applications. In this review, we summarize recent advances in SERS probe design and fabrication along three major directions: (i) engineering plasmonic hotspots with enhanced field confinement to achieve stronger and more uniform signals; (ii) analyte-directed strategies that precisely position and retain target molecules via tailored surface chemistries, nanoscale confinement, and on-surface reactions for single hotspot SERS; and (iii) hybrid architectures integrating plasmonic metals with functional materials, including high entropy materials, semiconductors, and graphene and other 2D materials, to synergistically couple electromagnetic and chemical enhancement mechanisms. Despite significant progress, key challenges remain for practical applications outside laboratories, including substrate reproducibility and stability, diverse analyte compatibility, unknown molecule identification and standardized quantitative performance in complex environments. We highlight emerging solutions, such as large-area nanomanufacturing for controlled nanoscale gaps, high-resolution Raman mapping for spatial–temporal characterization, density-functional-theory-guided molecular interpretation, and machine-learning-enabled spectral analysis. Advances in foundational AI models and data-driven discovery are positioning SERS to become an increasingly versatile platform, from decoding unknown molecular structures to analyzing complicated multi-component systems for environmental, biomedical, and national security applications with high sensitivity and selectivity. Full article

Melanin-like polymers, particularly polydopamine, have gained significant attention as photothermal materials due to their broad light absorption (ultraviolet to near-infrared), high photothermal conversion efficiency, negligible fluorescence, good biocompatibility regarding unmodified melanin-like polymers, and universal adhesion. Upon light irradiation, these bioinspired polymers convert absorbed optical energy into heat through molecular vibration and electron–phonon coupling, making them ideal for diverse photothermal applications. This review comprehensively summarizes recent advances in using melanin-like polymers for photothermal purposes. In biomedical engineering, they serve as efficient agents for photothermal therapy and synergistic antibacterial treatment. In catalysis, their photothermal effect enhances pollutant degradation, hydrogen production, and chemical warfare agent detoxification. For water remediation, melanin-like polymers are fabricated into evaporators, membranes, and aerogels for solar-driven steam generation, desalination, and oil spill cleanup. They also enable sensitive photothermal sensing, near-infrared imaging, and laser desorption ionization mass spectrometry imaging. Furthermore, these materials are incorporated into soft actuators and self-healing elastomers for light-controlled shape memory, programmable folding, and remote manipulation. Finally, we discuss remaining challenges such as long-term stability, biocompatibility, scalability, and color limitations and provide future perspectives for advancing melanin-like photothermal materials toward practical applications. Full article

The synthesis of n-bromobutane from n-butanol is a classic undergraduate organic chemistry experiment, primarily intended to illustrate the bimolecular nucleophilic substitution (S_N2) mechanism. However, this experiment is commonly plagued by low yields and the formation of byproducts (e.g., n-butene and di-n-butyl ether), which confuse students. To reveal the molecular origin of these competitive pathways, this study employs density functional theory (DFT) calculations to systematically investigate the reaction mechanism under acid catalysis. Four potential reaction pathways were explored: S_N2 substitution, E2 elimination, intermolecular etherification, and a high-energy E2 pathway. The computational results indicate that the S_N2 pathway to n-bromobutane is kinetically and thermodynamically favorable due to its low energy barrier. In contrast, the E2 elimination pathway possesses a higher energy barrier (18.8 kcal/mol vs. 13.5 kcal/mol for S_N2), explaining why elevated temperatures favor the formation of n-butene. Moreover, the etherification pathway was found to be the most energetically demanding, consistent with the trace amounts of di-n-butyl ether observed experimentally. These findings provide a quantitative molecular-level rationale for the strict temperature control and standardized reagent addition sequences in the laboratory protocol. By visualizing the potential energy surfaces, this computational approach bridges the gap between theoretical mechanism and practical operation, offering a valuable pedagogical tool for enhancing student understanding. Full article

Chirality has emerged as a critical determinant in the design, efficacy, and environmental behavior of modern insecticides. While a significant proportion of agrochemicals are inherently chiral, most are still commercialized as racemic mixtures, despite well-documented differences in biological activity, toxicity, and degradation pathways between enantiomers. In this review, we provide a comprehensive and critical analysis of advances in the stereoselective synthesis and resolution of chiral insecticides, with particular emphasis on neonicotinoids, pyrethroids, and oxadiazines, including indoxacarb. A systematic survey of the literature (1985–2025), including peer-reviewed articles and patents, reveals that multiple strategies have been developed to access enantiomerically enriched compounds, including asymmetric organocatalysis, transition-metal catalysis, chiral-pool approaches, biocatalytic transformations, and chromatographic resolution techniques. Among these, recent developments in photoredox catalysis, recyclable metal complexes, and enzyme-mediated processes have significantly improved enantioselectivity and scalability, bridging the gap between academic methodologies and industrial applications. Despite these advances, challenges remain in achieving cost-effective, sustainable, and universally applicable asymmetric processes. Importantly, the relationship between stereochemistry and biological performance underscores the need for integrating synthetic chemistry with toxicological and environmental studies. Future directions point toward the incorporation of green chemistry principles, continuous-flow processes, and computational tools, including machine learning and molecular modeling, to accelerate the rational design of enantiopure agrochemicals. This review highlights both the progress achieved and the critical gaps that must be addressed to realize the potential of stereoselective insecticide development fully. Full article

The microenvironment of the porous channels in enzyme immobilization carriers critically determines the catalytic performance of immobilized enzymes. In this study, we systematically tuned the hydrophobicity/hydrophilicity of the channel microenvironment of hydrogen-bonded organic frameworks (HOFs) by introducing four different substituents (-CH₃, -Cl, -F, -NH₂) at the 2-position of the phenyl ring of the HOF-101 monomer. These HOF-101 derivatives, which are isostructural to the parent HOF-101, were used to immobilize phosphotriesterase (PTE). The enzyme loading efficiencies ranged from 64.7% to 70.7%, indicating that the substituents had little effect on PTE binding, which primarily relies on carboxyl-residue interactions. Kinetic studies revealed that the hydrophilic -NH₂-functionalized HOF-101 (PTE@HOF-101-NH₂) exhibited the highest catalytic efficiency (1.43 × 10⁸ M⁻¹ s⁻¹), 2.27 times that of free PTE, while the hydrophobic -CH₃ analogue showed reduced activity. Notably, PTE@HOF-101-F demonstrated superior acid resistance (70% relative activity at pH 2) and long-term thermal stability (70% activity retention after 6 h at 70 °C), outperforming other derivatives. In contrast, PTE@HOF-101-NH₂ showed the highest activity under mild conditions but suffered from framework dissolution under prolonged harsh treatments. This work demonstrates that fine-tuning the HOF channel microenvironment is an effective strategy to enhance enzyme activity and stability, providing a platform for designing advanced immobilized enzyme systems. Full article

This study investigated rhamnolipid synthesis in Pseudomonas aeruginosa ATCC 27853. Two constitutive promoters, P_rpsJ and P_oprL, were isolated and cloned upstream of the rhlABRI and rmlBDAC gene clusters to evaluate their impact on rhamnolipid titers. The overexpression of rhlB, driven by the P_rpsJ promoter, significantly enhanced rhamnolipid production. Subsequent glycine-scanning mutagenesis of RhlB identified an optimal variant (RhlBM328G), which increased the titer 1.82-fold (to 24.6 g·L⁻¹) compared to the wild type, achieving a product yield of 0.39 g·g⁻¹. Characterization of the extracted rhamnolipids revealed a critical micelle concentration of 1 mg/L, a corresponding surface tension of 53.9 mN/m, and a hydrophilic–lipophilic balance (HLB) value of 14. This HLB value indicated that the synthesized rhamnolipids possess superior hydrophilicity, robust oil-in-water emulsifying capabilities, and excellent solubilization and dispersion properties. Furthermore, molecular docking and molecular dynamics simulations demonstrated that in the RhlBM328G mutant, the nucleophilic attack distances between the substrates and the catalytic moiety are optimized for catalysis, thereby boosting rhamnolipid production. Full article