Molecularly Engineered Nitro‐Functionalized Organic Electrode for High‐Efficiency Ammonium Removal and Resource Recovery via Capacitive Deionization

Abstract

The increasing discharge of ammonium‐rich wastewater has become a critical challenge for aquatic ecosystems and sustainable nitrogen management, creating an urgent need for efficient NH4+ removal and recovery technologies. Among emerging electrochemical approaches, capacitive deionization (CDI) is attractive because of its low energy consumption and mild operating conditions, yet its practical performance is still largely limited by electrode materials. In this study, we developed a nitro‐functionalized organic electrode based on dinitro‐isoquinoxaline (DNIQ), featuring a rigid fused‐ring π‐conjugated framework and well‐defined redox‐active sites. The introduced nitro groups markedly lower the LUMO energy level and redistribute electron density within the conjugated framework, while enhancing the interaction of the C═N and NO2 sites with NH4+. Experimental results show that the DNIQ electrode retains 81.84% of its capacity after 6000 cycles. When assembled into a CDI system, it delivers a record NH4+ removal capacity of 273.89 mg g−1 and an ultrafast removal rate of 42.39 mg g−1 min−1 at 1.4 V, while maintaining 100% capacity retention over 100 cycles. This work provides a molecular‐level strategy for efficient ammonium capture and sustainable nitrogen recovery.