Nitrophenols (NPs), classified as priority pollutantsdue to their significant toxicity, persistence, and bioaccumulation potential,pose severe threats to ecosystems and human health. Catalytic reduction,particularly the conversion of NPs like 4-nitrophenol (4-NP) to less toxicaminophenols using sodium borohydride (NaBH₄), represents apromising remediation strategy. While conventional metal-based catalysts facelimitations including high cost, poor durability, and potential metal leaching,carbon-based metal-free catalysts (C-MFCs) have emerged as highly efficient,sustainable, and cost-effective alternatives. However, the precise reactionmechanisms governing NP reduction over C-MFCs remain ambiguous, and significantdebate surrounds the nature of the active sites and the structure-activityrelationships dictating performance. This review systematically elucidates thecatalytic sites and associated reduction mechanisms in C-MFCs. Wecomprehensively summarize design principles centered on defect engineeringstrategies, encompassing single-atom (N, S, B, P, O), dual-atom (B,N; N,S;N,P), and tri-atom (B,N,F; N,P,F) doping, alongside non-doping defects such asedge and pore defects. The critical structure-performance relationships linkingthese engineered active sites to catalytic activity (e.g., turnover frequency,TOF) are analyzed, integrating experimental evidence and theoretical insights.Furthermore, strategies for constructing three-dimensional architectures toenhance active site accessibility and catalyst stability are highlighted. Thiswork provides fundamental insights to guide the rational design ofnext-generation high-performance C-MFCs for sustainable nitrophenol pollutioncontrol.

A series of ionic liquids 1-alkyl-3-methylim idazolebis(2-ethylhexyl) phosphate, were prepared, and the catalytic performance ofionic liquids was evaluated through the esterification reaction ofpentaerythrotol and hexanoic acid at a stoichiometric ratio as a modelreaction. The results showed that the [BMIM][DEHP] and [HMIM][DEHP] exhibitedgood catalytic activity. The [HMIM][DEHP] was chosen as a lubricant additive tofurther investigate the tribological properties after the reaction, and theresults for both COF and WSD and wear volume indicate that the introduction of[HMIM][DEHP] has improved the friction reducing and anti-wear properties ofpentaerythrotol tetra-hexanoate.

The Sr₂Fe_1.5Mo_0.5O_6-δ (SFMO) perovskite exhibits promising performance as a solid oxide fuel cell(SOFC) anode for hydrogen fuel but demonstrates limited catalytic activity withhydrocarbon fuels. To address this limitation, a Sr₂Fe_1.3Ni_0.2Mo_0.5O_6-δ (SFNMO) perovskite was developed via B-site Ni substitution, and its in-situ exsolution behavior and methane electrooxidation performance weresystematically investigated. Combined XRD, SEM, and TEM-EDS analyses revealthe in-situ exsolution of Ni-rich Ni-Fe alloy nanoparticles from theSFNMO matrix under a hydrogen atmosphere. A symmetrical SOFC employing Gd_0.1Ce_0.9O_2-δ (GDC) electrolyte and SFNMO electrodes achieved an initial maximum powerdensity of 82 mW cm^-2 in wet methane fuel at 800 ℃, which representsan approximately 33% improvement over the symmetrical cell with SFMO electrode(61 mW cm^-2). Remarkably, the cell maintained stable operation underconstant current for 50 h in methane fuel, with the peak power density furtherincreasing to 113 mW cm^-2, demonstrating the excellent catalyticactivity of the in-situ exsolved Ni-Fe nanoparticles for methaneconversion.

This study presents a sustainable approach for thegreen synthesis of iron nanoparticles (Fe(NPs)) using an aqueous extract of Psidiumguajava (guava leaves) as a reducing and stabilizing agent. The FeNPs wereapplied in the catalytic reduction of 4-nitrophenol. To minimize the use ofsodium borohydride (NaBH₄), different volumetric ratios of plantextract and NaBH₄ were tested. The influence of these ratios on thephysicochemical and morphological properties of the FeNPs was evaluated usingX-ray diffraction (XRD), scanning electron microscopy with energy-dispersiveX-ray spectroscopy (SEM/EDS), high-resolution field-emission SEM (HR-FESEM),Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis(TGA), and N₂ physisorption. Increasing the proportion of plant extract led toreduced crystallinity, larger particle sizes, and lower surface areas. Despitethese changes, using up to 40% extract improved catalytic performance,achieving over 90% reduction of 4-nitrophenol. Ecotoxicological assessmentsconfirmed the biocompatibility of the FeNPs, the effective neutralization of4-nitrophenol toxicity post-reduction, and highlighted the inherent toxicity ofNaBH₄. These findings demonstrate the potential of Psidiumguajava-mediated FeNPs as eco-friendly catalysts for pollutant reduction,combining efficiency with reduced environmental impact.

This study investigates the long-term mobilityand ecological risks of As, Zn, and Cd in calcium arsenic residue (CAR) undersimulated dry-wet (DW) and freeze-thaw (FT) cycles. Accelerated agingexperiments, combined with multiscale characterization (XRD, XPS, SEM, FTIR),revealed distinct transformation mechanisms. DW cycles promotedcarbonate-driven dissolution, As(III) oxidation to As(V) (resulting in an 18.4%increase in As(V) as shown by XPS), and sulfide oxidation (with reductions of47.7% in ZnS and 15.08% in CdS). These processes increased the acid-solublemetal fractions (F1: As by 11.3%, Zn by 6.0%, and Cd by 8.7%) and metal releaserates (52.39% for As, 42.63% for Zn, and 68.55% for Cd under DW conditions). Incontrast, FT cycles induced mechanical fracturing and ice-mediatedstabilization, which limited ion migration, partially amorphized ZnO, andpromoted the precipitation of Cd(OH)₂. Ecological risk assessmentsindicated rising risks, with integrated potential ecological risk indices(IPER) reaching 11,187.85 under DW conditions and 10,668.29 under FTconditions, with arsenic contributing over 80%. The Risk Assessment Code (RAC)reclassified all metals into moderate-risk categories (As: 11.9-19.7%, Zn:9.4-15.2%, Cd: 12.1-18.6%). Weibull modeling (α = 6.98-10.98, R² > 0.96) described the nonlinear kinetics, showing that cadmium aged thefastest (λ: Cd > As > Zn), with delayed but persistent risks under FTconditions. These results underscore the importance of developingclimate-resilient stabilization strategies. The integrated framework combiningmineral evolution, kinetics, and risk forecasting offers significant insightsfor managing legacy CAR pollution under changing climate conditions.

Selective hydrogenativedepolymerization of polyesters to diols is regarded as a promising strategyfor plastics upcycling. However, many catalysts documented in literature stillinvolve harsh reaction conditions, such as high temperature and high H₂ pressure. In this work, we present a PN³-rutheniumcomplex catalyzed polyesters upcycling into various highly value-addeddiols under mild reaction conditions using H₂ as a hydrogen source.It is worth noting that PLA depolymerizes into 1,2-propanediol under 1 MPahydrogen pressure at ambient temperature within 2 h; the conditions are muchmilder than those of previous reports. Aromatic polyester PET degradation needsharsher reaction conditions (80 ℃, 4 MPa, 3 h). The different reactionconditions enable direct separation of the degradation products of PLA and PETmixture via sequential depolymerization, as well asmixing them with polyolefins (PE, PP, PS). More strikingly, this catalyst isalso effective for the catalytic hydrogenation of polyesters in the presence ofethanol to afford various diols, avoiding the use of harsh reaction conditionsand an expensive autoclave.