Cationic covalent organic nanosheets for rapid and effective detection of phenoxy carboxylic acid herbicides residue emitted from water and rice samples.

Development of efficient and sensitive adsorbent for capturing phenoxy carboxylic acids (PCAs) from environmental and food samples is necessary because PCAs could threaten human health. Designing nanoparticle with multiple functional groups is beneficial to achieve the strong adsorption interaction and the specific recognition for target compound. In this paper, TpTG as an ionic covalent organic framework (ICOF), that could offer plenty of positive charges and hydrogen-bonding sites, was fabricated. TpTG achieved quicker, more sensitive enrichment for anionic PCAs. The analysis of binding affinity by density functional theory (DFT) demonstrated that PCAs bonded to TpTG primarily via electrostatic attraction, N  H···O and O  H···O, and C  H···π interaction. The quantitative approach indicated low limits of detection (0.016-0.036 ng·g for rice and 0.43-0.78 ng·L for water). Furthermore, successfully determining PCAs emitted from real samples indicated the applicability of TpTG.