Thermal runaway of organic peroxides in chemical production poses a persistent and severe challenge in the field of energy and safety. The ambiguous decomposition mechanism of peroxypropionic acid (PPA), a typical and unstable peroxide, hinders effective risk prevention and control. This study employs a multiscale computational approach integrating reactive molecular dynamics (ReaxFF MD) and density functional theory (DFT) to unravel, for the first time, the complete reaction network and energy evolution pathway of a PPA mixture under thermal runaway conditions at the atomic scale. Simulation results reveal that its decomposition follows a typical free radical chain reaction mechanism, progressing through three self-accelerating stages: initial homolytic initiation, a vigorous exothermic propagation dominated by hydrogen abstraction reactions, and final secondary decomposition of products driven by accumulated heat. DFT calculations precisely quantified the activation energy barriers and reaction enthalpies of key elementary steps, identifying the rate-determining steps that drive thermal runaway. Adiabatic experiments validated the intense exothermic characteristics predicted by the simulations. This work clarifies the microscopic driving forces behind PPA thermal runaway, providing crucial molecular-level insights and thermodynamic data for designing safer operational protocols and developing efficient inhibitors at an industrial scale.

Incorporating guest molecules into energetic crystal frameworks has proven to be an effective strategy for modulating microstructure and reaction mechanism. In this study, the regulatory mechanisms of guest molecules on the shock-induced intrinsic reactivity and reaction pathways of CL-20 were systematically investigated based on the neuroevolution potential. The results indicate that NCCH3 exhibits the strongest reaction-promoting effect, driving the system into a violent reaction stage rapidly. However, due to its low oxygen balance, both the detonation pressure and velocity are significantly reduced. In contrast, N2O and CO2 behave as weakly reactive, endothermic buffering guests at early stages, which delay the decomposition of CL-20 and enhance its detonation pressure. The temperature rise and detonation performance of CL-20/H2O2 are close to those of α-CL-20, while showing a certain inhibitory effect on the initial temperature increase. Reaction pathway analysis reveals that high pressure can activate additional pathways, including H abstraction, O migration, and NO2 abstraction, thereby promoting parallel reactions and radical capture. H2O and H2O2 promote radical reaction chains through endothermic processes and the release of OH/H radicals, with H2O2 exhibiting faster onset and higher intensity. CO2 and N2O primarily suppress decomposition by diluting active species and through reversible reorganization reactions, with N2O showing a more pronounced retardation effect. NCCH3 strongly promotes early stage decomposition by engaging in multiple reaction pathways, but the overall reaction proceeds incompletely at later stages. The polarity and size of guest molecules can modify the initial crystal structure, while their radical-generating capability and chemical reactivity determine how they participate in reactions, thereby jointly influencing the intrinsic reactivity and decomposition pathways of host-guest crystals.

Synthesis of fluorescent iron-doped carbon dots with Fenton activity for noninvasive dual-mode urinary uric acid monitoring toward point-of-care renal diagnostics.

Effects of coprecipitated Al and Si on the phase transformation of ferrihydrite and Sb(V) immobilization: Interactions and reaction mechanisms.

The acetyl peroxyl radical (CH3C(O)O2) is a key intermediate in the atmospheric oxidation of volatile organic compounds (VOCs). In clean regions (low NOx), reactions with the hydroperoxyl radical (HO2) dominate the fate of the CH3C(O)O2 radical. However, the detailed atmospheric reaction mechanisms and kinetics of the CH3C(O)O2 and HO2 radicals are still not fully understood. Therefore, in this study, the reaction mechanism and kinetics were investigated using quantum chemical calculations and chemical kinetics methods, and the ecotoxicity of the reaction precursors and products was evaluated using structure-activity relationships. In the atmosphere, the CH3C(O)O2 radical primarily exists as cis-CH3C(O)O2 and trans-CH3C(O)O2 isomers, both of which contribute to reactions with the HO2 radical. The reaction of the CH3C(O)O2 radical with the HO2 radical follows two distinct mechanisms: (i) a hydrogen-transfer mechanism on the triplet state potential energy surface (PES) and (ii) an addition-decomposition mechanism on the singlet state PES. The predicted apparent rate constant is 9.44 × 10-12 cm3 molecule-1 s-1 at 290 K and 1 atm, which is in good agreement with the experimental data. Kinetic analyses indicate that the dominant reaction pathways and product distributions vary significantly with temperature. In forested regions, where the HO2 radical concentrations are typically high, the combination of elevated HO2 radical and lower winter temperatures promotes the conversion of the CH3C(O)O2 radical into CH3COOH and O3. This process impacts both the acidity and the oxidative capacity of the atmosphere. However, during summer, higher temperatures extend the atmospheric lifetime of the CH3C(O)O2 radical, favoring the reaction with the HO2 radical to form the OH radical. This may help explain the observed higher concentrations of the CH3C(O)O2 radical and the OH radical in tropical rainforests. Ecotoxicity results indicate that some of the precursors of the acetyl peroxyl radical are potentially ecotoxic. However, after conversion to the CH3C(O)O2 radical and subsequent reaction with the HO2 radical, they degrade into environmentally friendly compounds. Overall, this study provides a comprehensive theoretical understanding of the atmospheric behavior and ecological impact of the CH3C(O)O2 radical, offering a basis for predicting its reactions under diverse atmospheric conditions and supporting atmospheric modeling and environmental management.

The spinel-type MnFe2O4 catalyst exhibits excellent performance for selective catalytic reduction (SCR) of NOX by NH3, yet the catalytic mechanism remains to be established. Herein, density functional theory (DFT) calculations were performed to unveil the active sites and molecular-level NH3-SCR reaction mechanism of the MnFe2O4 catalyst. The results indicate that the key reactants and products are chemically adsorbed on the MnFe2O4(100) surface. The surface 2-fold coordinated Mn atom is identified as the key active center for NH3 and NO adsorption, which plays an important role in initiating the SCR reaction. The NH2* species, generated from the first dehydrogenation of NH3, serves as a vital intermediate. Its further dehydrogenation is hindered by a very high energy barrier (323.03 kJ mol-1). Mechanistic analysis shows that the main reaction channel for NH3-SCR over the MnFe2O4 catalyst includes two steps: (1) NH2 production from NH3 dehydrogenation and (2) NH2-NO reaction. The NH2-NO reaction is the rate-limiting step due to its relatively higher energy barrier (121.56 kJ mol-1). The MnFe2O4 catalyst has a superior N2 selectivity because the energy barrier of N2O production is much higher than that of N2 production. This work not only advances the understanding of denitration at the molecular scale but also offers a theoretical basis for the rational design of efficient catalysts for NH3-SCR.

Reaction mechanisms and rational design of MOF catalysts: insights from microscopic simulations

The development of high-efficiency metal-free photocatalysts for eliminating endocrine-disrupting compounds continues to pose a considerable challenge. Herein, we report the rational design and fabrication of a green and efficient donor-acceptor heterojunction photocatalyst, PTQ10:Y6@CSC, via a robust π-π stacking strategy. Relative to the PTQ10:IEICO-4F system with weak π-π interactions, the PTQ10:Y6 heterojunction exhibits a significantly enhanced internal electric field, with an intensity 2.05 times greater. This reinforced internal electric field effectively promotes the dissociation of photogenerated excitons and extends the charge carrier lifetime to 1.473 ns (compared to 1.267 ns for PTQ10:IEICO-4F). As a result, the production efficiency of key reactive species (•O2- and h+) is substantially elevated, enabling the complete degradation of 20 ppm methyltestosterone within 40 min under simulated solar irradiation. The PTQ10:Y6@CSC composite also demonstrates remarkable cycling stability, retaining 97.89% of its initial activity after 16 consecutive runs. Moreover, combining density functional theory simulations with experimental analyses, this study elucidates the underlying photodegradation pathways and reaction mechanisms by identifying the vulnerable attack sites on the methyltestosterone molecule. These findings provide not only a high-performance photocatalytic system for endocrine-disrupting compounds remediation but also fundamental insights into the structure-property relationships governing π-π stacked heterojunctions.

Electron-rich graphene layer induces a H-down configuration of water molecules for efficient ammonia electrosynthesis from nitric oxide.

One-part binders from woody biomass fly ash and blast furnace slag: reaction mechanisms and microstructural evolution

Synergistic effects of seaweed powder and rheology modifiers on the reaction mechanism and pore architecture of geopolymer

This study focused on the critical environmental problem of harmful synthetic dyes being discharged into aquatic environments, which cannot be purified by conventional methods. We investigated the removal of methyl orange (MO) using Ceriporia lacerata RF-7, a recently discovered white-rot fungus, as a potent bioadsorbent. SEM and BET analyses of the biomass structure and texture revealed a complex, porous hyphae with sufficient surface area for dye adsorption, as well as a large specific surface area and mesoporous structure that promotes molecular diffusion. The efficiency of bioadsorption was significantly influenced by pH and temperature, achieving a maximum removal rate of 95.0% at pH 4. High removal efficiency was maintained up to 40°C, and at 30°C, the adsorption process was found to be thermodynamically spontaneous. This thermal stability shows that treating industrial wastewater does not require rigorous temperature control and is an energy-efficient method. Equilibrium results confirmed the Langmuir adsorption isotherm model (R2 > 0.999) and demonstrated a significant maximum monolayer adsorption capacity of 185.10 mg/g, surpassing many commercially available and biological adsorbents. Kinematic studies demonstrated that the bioadsorption process adheres to a pseudo-second-order reaction mechanism, indicating that the rate-limiting step is influenced by both definite chemisorption and surface interactions. Thermodynamic studies show that the process is spontaneous (∆G° < 0), is endothermic (∆H° = +58.20 kJ/mol), and leads to greater disorder at the solid-liquid interface (∆S° = +224.0 J/mol·K). These findings underscore RF-7 as a strong, environmentally friendly, and highly effective biosorbent, providing a sustainable approach for the efficient treatment of industrial wastewater contaminated with dyes.

Efficient removal of atrazine by phosphorylated nano zero-valent iron activated persulfate process: Performance, reaction mechanism and degradation pathway

To better utilize abundant supplies of methane, a catalyst is needed that can selectively activate it. Studies of the reactivity of methane with ions in the gas phase can provide insight into reaction mechanisms at specific catalytic sites. Recently, He et al. found, through mass spectrometric observations, that out of the 27 [TaxOy]- species investigated, only [TaO3]- formed an anion-methane complex, [TaO3CH4]- (Q. Li, Q.-Y. Liu, A. Zhao, and S.-G. He, Reactions between TaxOy- (x = 1-5, y = 0-7) cluster anions and C1-C3 alkanes, J. Chem. Phys., 2025, 163, 054303). In the present study, where we employed a synergistic combination of anion photoelectron spectroscopy and DFT calculations, the [TaO3]- isomer with a structure of O-Ta-O2, in which the Ta atom is bonded to a terminal O atom and an η1-superoxo [O2-] ligand, was found to form two activation complexes with methane. The geometrical structures of these two activation complexes, in which one and two C-H bonds are cleaved respectively, were determined by comparing the experimental and computational spectra. This reports the first spectroscopic confirmation of C-H bond activation by tantalum oxide anions.

Mechanistic elucidation of strictosidine synthase-catalyzed Pictet-Spengler reaction for rare piperazine-indole scaffold formation.

Study on the free radical reaction behavior and mechanism during the spontaneous combustion process of coals with different degrees of metamorphism

A novel method to enhance interlayer bond in 3D-printed concrete using dry-powder application of supplementary cementitious materials

Interfacial reaction mechanism and phase change induced strengthening of connecting necks in SiC porous ceramics

Mechanical Properties and Reaction Mechanisms of One-Part Alkali-Activated Materials Based on Coal-Based Synthetic Natural Gas Slag

Capturing carbon monoxide (CO) via ligand complexation offers a strategy to mitigate and control CO emissions. In this study, the interaction of CO with N-heterocyclic carbenes (NHCs) and their isoelectronic boron-substituted analogs (NHBs) is examined using density functional theory. Computed geometries, natural bond orbital (NBO) analysis, topology analysis, electron localization functions (ELF), and charge density difference (CDD) maps are employed to characterize the nature of CO binding. The boron-based systems consistently formed more stable CO adducts than traditional NHC ligands. Building upon this, a mixed ligand approach combining NHC and NHB on either side of CO resulted in exceptional stabilization for 1NO2-CO-2NH2 and 1NO2-CO-2CH3 complexes, with the reaction mechanism suggesting that NHC facilitates initial CO capture, followed by complex stabilization through NHB coordination. Charge analyses showed a clear redistribution of electron density in CO upon coordination, with reduced C-O bond order and distinct C-C and B-O bonds, while Natural orbitals for chemical valence (NOCV), and Charge decomposition analysis (CDA) confirmed predominant covalent interaction with an electron transfer from NHB to NHC fragment through CO and π-backdonation from NHC to CO. Such charge transfer and back bonding exist in pure NHC complexes; however, the extent of orbital interaction is significantly enhanced in the pure NHB and NHC-NHB mixed systems. These findings highlight the superior ability of NHC and NHB ligand combinations, particularly those with electron-withdrawing and electron-donating substituents, to trap CO, offering valuable insights into the design of main-group frameworks for toxic gas capture applications.