Engineering flower-shaped hierarchical micromotors on a sustainable biotemplate by teamed boronate affinity-based surface imprinting for effective separation of shikimic acid

Abstract

Self-propelled nano/micromotors are the frontier of separation materials because they are capable of converting external energy in the surrounding environment into kinetic energy for their autonomous movement. In this work, a bioinspired flower-shaped hierarchical teamed boronate affinity (TBA)-imprinted Pt-free micromotor is introduced based on waste rape pollen as a biotemplate due to its merits of sustainability, rich source and low price. Such micromotor, composed of MnO₂ nanosheets as a catalytic medium, Mg-Al layered double hydroxides (LDH) nanosheets as large surface area substrate and functional surface imprinted polymers as identification subject, exhibits autonomic motor behavior powdered by oxygen bubbles generated by the decomposition of H₂O₂ and selective recognition and separation for shikimic acid (SA). The hierarchical flower-shaped structure affords more accessible recognition sites for SA, which thus facilitates the separation process. Moreover, in combination with the TBA strategy, the micromotor can precisely recognize the target via boronate affinity between boronic acids and cis-diols from SA while showing strong binding capacity under neutral conditions. Benefiting from the pluripotent role of pioneering boronate affinity-covalent imprinted technique, hydrogen bonds interaction and nanoconfinement effect, the resulting affinity towards SA is evidently enhanced with maximal adsorption capacity of 129.51 mg g⁻¹ at neutral pH in the presence of H₂O₂. After five capture/release cycles, the adsorption capacity remains above 85 %. This proposed flower-shaped hierarchical micromotor expands the scope of potential materials for the adsorption of SA and provides a new and promising direction for fabricating adsorbents applied in the separation and purification of natural products.