Highly flexoelectric response for uranium removal and recovery using the organic-inorganic hybrid material.

Abstract

Catalysis was an effective method for uranium recovery and environmental remediation. However, the weak flexoelectric response, despite being universal in dielectric materials, greatly limited its appeal for research and catalytic applications. Here, we proposed a strategy to enhance the flexoelectric response by bridging inorganic chains with metal-organic chains within the structure. The resulting hybrid material, Co[C₄H₄N₂]V₂O₆, demonstrated excellent uranyl removal performance, surpassing that of state-of-the-art piezocatalysts. Co[C₄H₄N₂]V₂O₆ showed flexocatalytic uranyl activity across a broad pH range and under high-salinity conditions. Under a dynamic experimental setup, Co[C₄H₄N₂]V₂O₆ showed strong potential for practical flexocatalytic applications. Co[C₄H₄N₂]V₂O₆ could efficiently separate uranyl in contaminated potable water, reducing the uranium concentration (~2.0 ppm) to below the drinking water standard (30 ppb). It could also lower the uranium concentration (~5.6 ppm) in mining wastewater to below the discharge limit (300 ppb). Its intrinsic anisotropic mechanical properties and cantilever-like morphology endowed high deformability, which, together with a large dielectric constant, enhanced its flexoelectric polarization. The revealed flexocatalytic mechanism confirmed that uranyl was converted into insoluble (UO₂)O₂·2H₂O by active species generated through dynamic polarization. This work provided a promising avenue for the design of advanced flexocatalysts and offered an effective strategy for uranium recovery and environmental remediation.