Kinetic Studies on the Oxoiron(IV) Complex with Tetradentate Aminopyridine Ligand PDP*: Restoration of Catalytic Activity by Reduction with H2O2

Pyrite-activated persulfate to degrade 3,5,6-trichloro-2-pyridyl in water: Degradation and Fe release mechanism

TCP (3,5,6-trichloro-2-pyridinol), the main recalcitrant degradation product of chlorpyrifos, poses a high risk to human health and ecological systems. This study provided a comprehensive exploration of the pyrite-activated persulfate (PS) system for the removal of TCP in water and placed particular emphasis on the pyrite oxidation process that releases Fe. The results showed that the pyrite-activated PS system can completely degrade TCP within 300 min at 5.0 mmol/L PS and 1000 mg/L pyrite at 25 °C, wherein small amounts of PS (1 mmol/L) can effectively facilitate TCP removal and the oxidation of pyrite elements, while excessive PS (>20 mmol/L) can lead to competitive inhibitory effects, especially in the Fe release process. Aimed at the dual effects, the evident positive correlation (R2 > 0.90) between TCP degradation (kTCP) and Fe element release (kFe), but the value of k (0.00237) in the pyrite addition variable experiment was less than that in the PS experiment (k = 0.00729), further indicating that the inhibition effect of excessive addition consists of PS but not notably pyrite. Moreover, the predominant free radicals and non-free radicals produced in the pyrite/PS system were tested, with the order of significance being •OH < Fe (Ⅳ) < SO4•- < •O2- < 1O2, wherein 1O2 emerged as the principal player in both TCP degradation and Fe release from the pyrite oxidation process. Additionally, CO32- can finitely activate PS but generally slows TCP degradation and inhibit pyrite oxidation releasing Fe process. This study provides a theoretical basis for the degradation of TCP using pyrite-activated PS.

Harmonizing Enzyme-like Cofactors to Boost Nanozyme Catalysis

Engineering isolated metal sites resembling the primary coordination sphere of metallocofactors enables atomically dispersed materials as promising nanozymes. However, most existing nanozymes primarily focus on replicating specific metallocofactors while neglecting other supporting cofactors within active pockets, leading to reduced electron transfer (ET) efficiency and thus inferior catalytic performances. Herein, we report a metal-organic framework UiO-67 nanozyme with atomically dispersed iron sites, which involves multiple tailored enzyme-like nanocofactors that synergistically drive the ET process for enhanced peroxidase-like catalysis. Among them, the linker-coupled atomic iron site plays a critical role in substrate activation, while bare linkers and zirconia nodes facilitate the ET efficiency of intermediates. The synergy of three nanocofactors results in a 4.29-fold enhancement compared with the single effort of isolated metal site-based nanocofactor, holding promise in immunoassay for sensitive detection of chlorpyrifos. This finding opens a new way for designing high-performance nanozymes by harmonizing various nanocofactors at the atomic and molecular scale.

Bioinspired Heterobimetallic Photocatalyst () for Visible-Light-Driven C-H Oxidation of Organic Substrates via Dioxygen Activation

We report a bioinspired heterobimetallic photocatalyst RuIIchrom-FeIIIcat and its relevant applications toward visible-light-driven C-H bond oxidation of a series of hydrocarbons using O2 as the O-atom source. The RuII center absorbs visible light near 460 nm and triggers a cascade of electrons to FeIII to afford a catalytically active high-valent FeIV═O species. The in situ formed FeIV═O has been employed for several high-impact oxidation reactions in the presence of triethanolamine (TEOA) as the sacrificial electron donor.

pH Changes That Induce an Axial Ligand Effect on Nonheme Iron(IV) Oxo Complexes with an Appended Aminopropyl Functionality

Nonheme iron enzymes often utilize a high-valent iron(IV) oxo species for the biosynthesis of natural products, but their high reactivity often precludes structural and functional studies of these complexes. In this work, a combined experimental and computational study is presented on a biomimetic nonheme iron(IV) oxo complex bearing an aminopyridine macrocyclic ligand and its reactivity toward olefin epoxidation upon changes in the identity and coordination ability of the axial ligand. Herein, we show a dramatic effect of the pH on the oxygen-atom-transfer (OAT) reaction with substrates. In particular, these changes have occurred because of protonation of the axial-bound pendant amine group, where its coordination to iron is replaced by a solvent molecule or anionic ligand. This axial ligand effect influences the catalysis, and we observe enhanced cyclooctene epoxidation yields and turnover numbers in the presence of the unbound protonated pendant amine group. Density functional theory studies were performed to support the experiments and highlight that replacement of the pendant amine with a neutral or anionic ligand dramatically lowers the rate-determining barriers of cyclooctene epoxidation. The computational work further establishes that the change in OAT is due to electrostatic interactions of the pendant amine cation that favorably affect the barrier heights.