Mechanical Reprogramming of Ion Selectivity at Nanoconfined Piezoelectric Interfaces

ABSTRACT Adsorption‐based ion separation is commonly controlled by pore architectures and binding‐site chemistry. However, for chemically similar oxo‐metal species such as uranium (U) and vanadium (V), static pores and predesigned coordination sites have limited ability to amplify subtle differences in interfacial reactivity. Here, we report a nanoconfined BaTiO 3 ‐ graphene oxide (GO) piezoelectric interface for mechanically programmed U/V selectivity. Electric‐field‐guided crystallization enables the room‐temperature growth of ultrathin BaTiO 3 nanosheets within GO galleries, converting passive lamellar channels into chemically coupled nanoconfined BaTiO 3 ‐GO interfaces. These interfaces integrate ion‐accessible coordination sites, interfacial charge‐transport pathways, and mechanically activatable polarization within nanoconfined environments. Under quasi‐static conditions, adsorption is affinity‐governed and favors uranyl capture. Upon ultrasonic activation, the BaTiO 3 ‐GO interfaces generate dynamic polarization charges and promote interfacial charge redistribution, thereby inducing localized hydroxyl radical‐related interfacial chemistry and reshaping the local redox/coordination microenvironment. This coupled process promotes oxygen‐mediated V‐O coordination/immobilization while weakening competitive uranyl adsorption. Consequently, selectivity reverses from U favored to V‐preferential. In spiked simulated seawater, the interfaces achieve a V uptake of 71.43 mg·g −1 , a V/U separation factor of 102.08, and recyclable adsorption performance. This work demonstrates a nanoconfined piezoelectric‐interface design strategy for mechanically programmed ion selectivity beyond static pore‐size and binding‐affinity control.