Recently, single-atom catalysts (SACs) have been used to construct biosensors for the determination of organophosphorus pesticides (OPs). However, most nanozymes including SACs are peroxidase-like enzymes and require highly toxic and unstable hydrogen peroxide (H 2 O 2 ) as a co-reactant to generate reactive oxygen species. Inspired by the heme site of cytochrome c oxidases (Ccos), the construction of Fe-N 5 -coordinated SACs by introducing axial N ligands is expected to bind O 2 to generate active metal−oxygen intermediates. Herein, a SAC with an Fe-N 5 active center confined by hierarchically porous carbon nanoframes (Fe SAs/N 5 -pC-4) was prepared by a polymerization−pyrolysis− evaporation−etching strategy, and its underlying enzyme-like mechanism was uncovered through experiments and density functional theory calculations. The 100% metal atom utilization, increased accessible active sites, accelerated mass transfer, excellent hydrophilicity, and an electron-driven mechanism of axial N endow the SAC with enhanced oxidase-like activity. Notably, its catalytic rate constant (0.398 s −1 ) is 569 times greater than that of the commercial Pt/C catalyst. Similar to the catalytic mechanism of Ccos, O 2 can be converted into reactive oxygen species, avoiding the use of co-reactant H 2 O 2 effectively. In addition, based on the inhibitory effect of thiols on the active site of Fe SAs/N 5 -pC-4, a biosensor was constructed and applied to the colorimetric analysis of OPs. This provides a facile, cost-effective method for efficient OP screening at sites to help control their contamination.

No abstract

Liquid-crystal monomers (LCMs), especially fluorinated biphenyls and analogues (FBAs), are identified to be an emerging generation of persistent organic pollutants. However, there is a dearth of information about their occurrence and distribution in environmental water and lacustrine soil samples. Herein, a series of fluorine-functionalized Scholl-coupled microporous polymers (FSMP-X, X = 1–3) were designed and synthesized for the highly efficient and selective enrichment of FABs. Their hydrophobicity, porosity, chemical stability, and adsorption performance (capacity, rate, and selectivity) were regulated preciously. The best-performing material (FSMP-2) was employed as the on-line fluorous solid-phase extraction (on-line FSPE) adsorbent owing to its high adsorption capacity (313.68 mg g–1), fast adsorption rate (1.05 g h–1), and specific selectivity for FBAs. Notably, an enrichment factor of up to 590.2 was obtained for FSMP-2, outperforming commercial C18 (12.6-fold). Also, the underlying adsorption mechanism was uncovered by density functional theory calculations and experiments. Based on this, a novel and automated on-line FSPE-high-performance liquid chromatography method was developed for ultrasensitive (detection limits: 0.0004–0.0150 ng mL–1) and low matrix effect (73.79–113.3%) determination of LCMs in lake water and lacustrine soils. This study offers new insight into the highly selective quantification of LCMs and the first evidence for their occurrence and distribution in these environmental samples.