Engineering <scp>S</scp> ‐scheme <scp>NiCoMn</scp> ‐ <scp>LDH</scp> /kaolinite heterojunction from spent battery recycling: synergistic photocatalysis for <scp>CO</scp> ₂ reduction and biomass valorization

Abstract BACKGROUND The simultaneous valorization of waste batteries, CO₂, and biomass holds significant importance for advancing a circular economy. RESULT In this work, valuable metals (Ni, Co, Mn) were recovered via an acid‐leaching and reduction method. These recovered metals were subsequently employed to in‐situ grow NiCoMn layered double hydroxide (LDH) on kaolinite (Kaol) nanosheets through a microwave‐assisted hydrothermal process. This strategy successfully constructs an S‐scheme heterojunction composite photocatalyst (NiCoMn‐LDH/Kaol) for the efficient coupling of photocatalytic CO₂ reduction with 5‐hydroxymethylfurfural (HMF) oxidation. Results demonstrated that the NCM‐LDH‐9/Kaol catalyst prepared at pH = 9 achieved the highest CO production rate of 235 μmol·g⁻ 1 ·h⁻ 1 and an exceptional 92.2% selectivity towards 2,5‐diformylfuran (DFF) from HMF oxidation under full‐spectrum irradiation. Mechanistic studies revealed that the S‐scheme heterojunction between LDH and Kaol significantly enhanced the separation of photogenerated charge carriers. Simultaneously, the oxidation of HMF provides the necessary protons for CO₂ reduction, establishing a synergistic enhancement. CONCLUSION This work presents a novel strategy for the high‐value utilization of spent batteries and the coupled conversion of biomass and CO₂, offering dual environmental and energy benefits. © 2025 Society of Chemical Industry (SCI).