Controllable removal/release of phosphate by light-responsive layered double hydroxide composite electrode

Dynamic phosphate regulation is crucial for environmental protection and sustainable phosphorus management. In this work, we developed a smart electrode by electrochemically engineering photo-responsive poly(azobenzene) into MgMn-layered double hydroxide interlayers (MgMn-LDH/Pazo) for light-switchable capacitive phosphate removal and recovery from aqueous environments. Under UV light irradiation, the trans-to-cis photoisomerization of intercalated Pazo induces the formation of multiple bonding interactions with phosphate ions, leading to an enhanced phosphate adsorption capacity from 14.08 to 55.22 mg-PO ₄ /g. Upon switching to visible light, the cis-to-trans isomerization of Pazo decreases the binding affinity toward phosphate, achieving an efficient phosphate desorption with a regeneration rate of 84.6%. This optically switchable system enables selective, reversible, and tunable phosphate uptake and release, offering a sustainable solution for environmental remediation and phosphorus resource recovery. The proposed innovative strategy demonstrates excellent phosphate removal/release performance with operational controllability, positioning it as a promising candidate for next-generation smart wastewater treatment technologies.