A selective oxidation strategy for deciphering the structure-function relationships of dissolved organic matter

Natural dissolved organic matter (DOM) is widespread in the environment and influences various environmental processes through its redox-active carbonyl groups, such as aromatic ketones/aldehydes and quinones. Selective reduction of these redox-active carbonyls by NaBH₄ has achieved great success, however, there is no ready method to selectively oxidize corresponding hydroquinone moieties. Here we achieved first selective aerobic oxidation of hydroquinones to corresponding quinones in DOM by the nanozyme (CDPGA-Cu), evidenced by multiple spectral identifications; this method provides superior selectivity compared with other oxidants such as MnO₂, Cl₂ or ozone. And this treatment leads to decreased emission along with insignificant change of both absorption from DOM and photoproduction of Au NPs by DOM, confirming quinone contributes much less to intramolecular charge-transfer interactions in DOM compared with non-quinone moieties such as aromatic ketones. We posit that this method could revolutionize NOM related studies as NaBH₄ selective reduction method does.