Recyclable Green Synthesis of Cu 2 O Octahedra via Coordination‐Induced Surface Reconstruction With Exceptional Glucose Electrooxidation

ABSTRACT Coordination‐chemistry‐driven reconstruction offers a powerful yet largely unexplored route for transforming bulk metals into functional nanomaterials with programmed surface states. Herein, we report a green, recyclable wet‐chemical protocol that integrates top‐down oxidative dissolution of copper with bottom‐up crystallization to produce octahedral Cu 2 O submicron crystals. In a strongly alkaline medium, transient Cu–NH 3 coordination promotes coordination‐driven oxidative dissolution of scrap copper to generate a metastable [Cu(OH) 4 ] 2– aqueous precursor, while aldehyde‐functionalized dextran (ODex) serves as a mild reductant and a surface‐coordinating ligand. A self‐catalytic acceleration pathway enables rapid room‐temperature crystallization within minutes, ODex‐regulated octahedral Cu 2 O (ODex‐Octa‐Cu 2 O) exposing {111} facets, decorated with ODex–Cu 2+ complexes and stabilized Cu‐vacancy‐rich relaxed atomic layers. This coordination‐induced surface reconstruction tailors the surface electronic and defect structure; density functional theory further reveals the Frontier orbital theory evolution upon ODex–Cu 2+ modification of Cu 2 O(111) and the concomitant work function regulation, which together stabilize the lattice and optimize interfacial adsorption‐desorption kinetics. Meanwhile, ODex‐Octa‐Cu 2 O exhibits ultrahigh mass‐normalized activity for 4‐nitrophenol hydrogenation ( k nor = 32.36 s −1 mg −1 mL), benefiting from the in situ generated surface‐active hydrogen, and efficient glucose electrooxidation enabling a bifunctional glucose fuel cell. The fully recyclable alkaline medium further realizes a sustainable “metal‐to‐nanomaterial” conversion route.