Delocalized π-electron polymeric nanoflowers with dual redox functionalities for high-capacity and ultrafast capacitive removal of Sr(II).

The remediation of radioactive wastewater containing hazardous Sr(II) is critical for environmental safety and public health, driving demand for efficient water purification technologies. Capacitive deionization (CDI) has emerged as a promising electrochemical strategy for ion removal; however, its efficiency in capturing Sr2+ remains limited by the scarcity of suitable high-performance electrode materials. Herein, we develop a polymeric nanoflower material, Poly-Triphenylene-Tetracarboxyl-Perylene (PTTP), with an intrinsically delocalized electronic structure for use as an advanced CDI electrode to electrochemically capture Sr2+. The unique nanoflower architecture not only enhances Sr2+ permeability and diffusion but also, in synergy with its π-electron-rich stabilized backbone, facilitates extended electron delocalization across the polymer framework. Besides, the deliberate introduction of carbonyl and imine functionalities provides electronically optimized binding sites for Sr2+ uptake, as verified by in-situ characterizations, theoretical calculations, and molecular dynamics simulations. When implemented in a CDI cell, the PTTP electrode delivers an outstanding Sr2+ removal capacity of 48.2 mg g-1, a rapid rate of 3.1 mg g-1 min-1, and long-term stability with ∼98.9% retention at 1.2 V. This exceptional CDI performance highlights the promise of PTTP for treating radioactive effluents.