Hierarchically Macroporous Ce-MOF Nanozyme with Enhanced Phosphoester Hydrolase- and Oxidase-like Activities for Self-Cascade Colorimetric Detection of Profenofos On-Site

The extensive application of profenofos (PFF), a widely used organophosphorus pesticide (OP), has raised significant environmental and health concerns due to its accumulation in ecosystems and its inhibitory effects on acetylcholinesterase in humans. Despite advancements in analytical technologies, currently available chromatography and electrochemical assays often involve complex procedures, high costs, and specialized equipment, limiting their applicability for routine and on-site PFF monitoring. Here, we report a novel self-cascade nanozyme-based colorimetric biosensor employing a hierarchically macroporous Ce-MOF (HMUiO-66(Ce)) with integrated phosphoester hydrolase (PEH)- and oxidase (OXD)-like activities. The HMUiO-66(Ce) nanozyme features hierarchical macrochannels that enhance mass transfer and substrate accessibility, significantly improving its cascade sensing performance compared with conventional UiO-66(Ce). Through PEH-OXD cascade catalysis, PFF is hydrolyzed into 4-bromo-2-chlorophenol, which undergoes selective oxidative coupling via OXD-like catalysis, yielding a distinct red-colored product. This colorimetric response is highly specific to PFF, as other organophosphates do not trigger the OXD-catalyzed coupling, minimizing interference and ensuring high analytical selectivity. The colorimetric biosensor can be seamlessly integrated with a smartphone for on-site detection, exhibiting a broad linear detection range (0.1-50 μg/mL) and an impressively low detection limit (0.068 μg/mL), surpassing most existing colorimetric methods. This work provides new insights into the development of a highly sensitive and selective biosensor through the self-cascade principle, offering great potential for on-site screening of environmental pollutants.