<p>The pervasive spread of nano- and microplastics (NMPs) presents pressing environmental and health challenges and conventional approaches struggle to achieve both the efficient adsorption and precise detection of label-free NMPs, especially at the nanoscale in complex real-world matrices. Here we report a multifunctional copper-doped polydopamine-functionalized magnetic silica adsorbent that integrates robust interfacial adhesion, photothermal activity and laccase-like catalytic activity, enabling the rapid capture and on-site detection of label-free NMPs. This hierarchical design can capture NMPs ranging from the nano- to micrometre scale within 3 minutes and maintains robust performance over multiple reuse cycles under mild conditions. Leveraging its laccase-like catalytic activity, the developed adsorbent serves as a surface-responsive platform for the broad-spectrum on-site detection of various label-free NMPs, even at the nanoscale. Multivariate analysis via machine learning methods further distinguishes NMP species and concentrations with high specificity. Density functional theory calculations confirm that non-covalent interactions dominate the NMP adsorption mechanism. Impressively, this adsorbent demonstrates the reliable capture and on-site detection of low-concentration label-free NMPs in natural water sources and real-life scenarios (plastic cups, bowls and tea bags). This work overcomes the fundamental limitations of single-mode adsorption or label-based detection of traditional NMP treatment and analysis approaches, pioneering a new paradigm for efficient NMP removal and portable on-site analysis.</p>