Selective Functionalization of Graphene Oxide Unlocks Synergistic Catalysis for Organophosphate Degradation

Abstract Site-selective functionalization of nanomaterials such as graphene oxide (GO) is a powerful strategy to tailor catalytic performance, with the degree and positioning of functional groups being critical for targeted applications. Herein, we present a systematic study on the functionalization of GO with ethylenediamine through two distinct pathways: (i) attachment at carboxylic acid groups located at the sheet edges and (ii) attachment at epoxide groups distributed across the basal plane. Comprehensive characterization, including XPS, AFM-IR, among others, was consistent with the site-specific functionalization. Importantly, the positioning effect was directly correlated with catalytic activity in the heterogeneous degradation of hazardous organophosphates─compounds widely used in agrochemicals and notorious for their extreme toxicity and persistence in the environment. Our results reveal that functionalization at the epoxide sites, despite yielding a lower degree of modification, produced superior catalytic efficiency, achieving a rate constant of 4.86 min–1 g–1, in contrast to 0.721 min–1 g–1 for the nanocatalyst functionalized via the carboxylic acid. The higher catalytic rate constant was obtained due to synergistic interactions with freely available carboxylic acids acting as intramolecular catalysts. Blocking these carboxylic acids with inert groups led to a marked decrease in activity, emphasizing their mechanistic role. Beyond advancing toward functionalization strategies, this study demonstrates how nanodesign can be leveraged to probe catalytic mechanisms and enhance detoxification of organophosphates. Understanding these synergistic effects in GO-based materials opens new avenues for designing nanocatalysts aimed at mitigating the dual-use hazards of organophosphates, with broad implications for environmental remediation and public health protection.