Congyun Zhang

Despite extensive advances in polyethylene terephthalate (PET) depolymerization, the molecular-level mechanisms by which solvents and cosolvents regulate PET swelling, transport, and bond cleavage remain insufficiently understood. Herein, an integrated molecular dynamics (MD) and density functional theory (DFT) calculation was employed to systematically elucidate the roles of eight representative cosolvents─tetrahydrofuran (THF), 2-methyltetrahydrofuran (M-THF), 1,3-dioxolane (DOL), δ-valerolactone (DVL), cyclopentanone (CP), ethylene glycol (EG), anisole (AS), and benzyl alcohol (BnOH)─in PET solvation and degradation-related environments. Analyses of free-volume evolution, diffusion behavior, and electronic structure-derived descriptors capturing local polarity and orbital localization reveal pronounced solvent-dependent differences in chain relaxation, molecular mobility, and electronic activation pathways. Ether- and carbonyl-containing cosolvents primarily promote PET swelling and molecular transport by modulating local polarity and chain relaxation, whereas the protic cosolvent benzyl alcohol forms a dynamically reconfigurable, ethylene glycol-coupled hydrogen-bond network that enhances molecular mobility and stabilizes reactive oxyanion/transition-state structures. These distinct interaction modes give rise to computed differences in activation barriers, which elucidate the depolymerization mechanisms of different cosolvents. This study establishes a unified transport–activation mechanistic understanding and provides theory-guided principles for the rational design of efficient cosolvent systems for PET recycling.

Chemical recycling to monomer (CRM) represents a highly efficient closed-loop strategy, yet selective recovery of polymerization-grade monomers from aliphatic polyesters remains challenging. Herein, we report a multifunctional zinc salt strategy for the closed-loop recycling of poly(ε-caprolactone) (PCL), in which zinc acetate serves triple roles in the polymerization, depolymerization, and crystallization regulation of the regenerated polymer. Compared with 0.25 wt % Zn(acac)2, which afforded ε-CL with 98.0% purity at 260 °C, ball-milled Zn(OAc)2 (Zn(OAc)2-BM) reduced the depolymerization temperature to 200 °C and produced recovered ε-CL (r-ε-CL) with 98.7% purity. Density functional theory (DFT) calculations combined with localized orbital locator (LOL) analysis demonstrated that stronger Zn2+ coordination and polarization of the carbonyl oxygen, coupled with the higher conformational flexibility of acetate ligands, significantly weakened the adjacent ester C–O bond ( the relaxed force constant reduced by 26.4%) and lowered the Gibbs free energy of activation by ∼10 kcal mol–1 relative to Zn(acac)2. Unpurified r-ε-CL was directly repolymerized into regenerated PCL (re-PCL) using Zn(OAc)2-BM, which enhanced crystallization kinetics and mechanical performance through residual heterogeneous nucleation. Under the optimized conditions, Zn(OAc)2-BM forms a dehydrated, less crystalline Zn(II) acetate based material containing a minor ZnO phase, enabling selective PCL recycling and improving the properties of re-PCL.

The high-rate electrocatalytic CO₂ reduction reaction (CO₂RR) to afford multicarbon products (C₂) holds transformative potential for advancing sustainable energy systems. Ionic liquids (ILs) have emerged as dynamic modulators to promote the C₂ pathway, yet the underlying atomistic mechanisms of ILs in modulating this CO₂RR process remain fundamentally unclear. Here, by integrating molecular dynamics (MD) simulations, density functional theory (DFT) calculations, and experimental validations, we systematically elucidate the critical influence of 1-(3-aminopropyl)-3-methylimidazole chloride ILs in optimizing the CO₂RR pathway on Cu surfaces through electronic structure engineering. MD simulations demonstrate that ILs establish a CO₂-enriched interfacial microenvironment that restricts bulk-phase CO₂ diffusion through the confinement effect. Electron structure analyses reveal that ILs synergistically enhance interfacial electron accumulation and directional charge transfer for adsorbed CO₂ and key intermediates (*CO, *COH, *CHO, and *C), collectively stabilizing them through IL-induced strengthening of Cu-C bonding. More importantly, the introduction of ILs dramatically reduces the activation barrier of the rate-determining C-C coupling step and thermodynamically favors the CO₂RR to C₂H₄ and C₂H₅OH pathways through atom orbital hybridization. Additionally, the ILs not only enhance the CO₂RR but also suppress the hydrogen evolution reaction (HER) through proton confinement. This work provides molecular-level insights into the dynamic role of ILs in optimizing CO₂RR processes and offers a foundation for designing advanced IL-mediated electrocatalytic systems.

The electrocatalytic CO₂ reduction reaction (CO₂RR) into value-added multi-carbon C₂₊ products holds significant promise for sustainable chemical synthesis and carbon-neutral energy cycles. Among the various strategies developed to enhance CO₂RR, the use of ionic liquids (ILs) has emerged as a powerful approach for modulating the local microenvironment and electronic structure of Cu-based metal catalysts. In this study, to unravel the molecular-level mechanisms underlying these enhancements, density functional theory calculations (DFTs) were employed to systematically explore how ILs with different terminal groups modulate the electronic reconstruction of the Cu surface, further affecting the *CO–*CO coupling and product selectivity. Electronic structure analyses reveal that ILs bearing polar moieties (–SH, –COOH) can synergistically enhance the interfacial electron accumulation and induce an upshift of the Cu d-band center, thereby strengthening *CO adsorption. In contrast, nonpolar IL (CH₃) exhibits negligible effects, underscoring the pivotal role of ILs’ polarity in catalyst surface-state engineering. The free energy diagrams and transition state analyses reveal that ILs with polar groups significantly lower both the reaction-free energy and activation barrier associated with the *CO–*CO coupling step. This energetic favorability selectively inhibits the C₁ product pathways and hydrogen evolution reaction (HER), further improving the selectivity of C₂ products. These theoretical insights not only unveil the mechanistic origins of IL-induced performance enhancement but also offer predictive guidance for the rational design of advanced IL–catalyst systems for efficient CO₂ electroreduction.

Lateral growth of thin films is crucial for organic electronic devices, such as field-effect transistors. Here, we report a strategy to improve the lateral growth of pentacene films using rubrene as a surfactant-like additive. Atomic force microscopy (AFM) images confirm the enhanced lateral growth with the presence of rubrene, resulting in smooth and enlarged molecule domains in the films in comparison to those without rubrene. Molecular dynamics simulations are conducted to explore the interlayer diffusion of pentacene molecules during the growth. With the rubrene molecules as surfactant-like additives, mean square displacement (MSD) analysis shows that the pentacene molecules have a descending diffusion coefficient of 2.0 x 10(-5) cm(2) s(-1), which is greater than the ascending diffusion coefficient of 1.6 x 10(-5) cm(2) s(-1). The more descending molecules lead to an enhanced lateral growth of pentacene films, which is in good agreement with the experiments. As a result, the pentacene films grown with rubrene exhibit a rapid increase in carrier mobility over thickness due to the well-connected domains resulting from enhanced lateral growth. This finding will provide a new strategy to modulate the morphology of organic films for high-performance devices.

A novel functionalized graphene oxide (f‐GO) decorated with phosphorus/nitrogen (P/N)‐containing molecules is fabricated using a facile water‐based procedure. The chemical structure and micro‐morphology are well characterized by a combination of experimental and theoretical methods. Reactive force field‐based molecular dynamics simulations reveal at the atomic level that the GO sheets are successfully functionalized with P‐N flame‐retardant molecules by means of hydrogen bonds. Subsequently, f‐GO with extremely low loading is introduced into epoxy resin (EP) for reducing its flammability. Thermogravimetric analysis suggests that f‐GO significantly reduces the maximum mass loss rate of EP and enhances the char‐yield during heating. Combined with the results of a microscale combustion calorimeter and limiting oxygen index, EP/f‐GO2 shows better flame retardancy than the other nanocomposites. Furthermore, the presence of 2 wt% f‐GO substantially reduces the fire hazard of EP, resulting in 29.3% decline in the peak heat release rate, as well as 73% and 65% reduction in total smoke production and rate of smoke release, respectively, according to cone calorimetric tests. Based on the analyses of the char layers, f‐GO is determined to promote the formation of a more protective phosphorus‐containing char barrier for EP during combustion, indicating an effective condensed phase flame‐retardant mechanism.