Ligand-stabilized Cu⁺/Cu²⁺ redox cycling in a water-stable cyamelurate coordination polymer for selective aerobic alcohol oxidation

Water-stable coordination polymers are highly desirable for green catalytic processes, yet systems based on cyamelurate ligands remain largely unexplored, despite their unique electronic structure and multiple coordination sites. Herein, we report a water-stable copper–cyamelurate coordination polymer (Cu-CP) featuring a mixed-valence Cu⁺/Cu²⁺ redox system synthesized under mild, aqueous, and environmentally benign conditions using earth-abundant and non-toxic precursors. Comprehensive characterization by XRD, FTIR, UV–Vis, XPS, EPR, and electron microscopy confirmed the formation of a crystalline polymeric framework comprising Cu⁺/Cu²⁺ sites, which are directly coordinated by nitrogen- and oxygen-donor atoms from cyamelurate ligands. The Cu-CP exhibited excellent catalytic activity toward the aerobic oxidation of benzyl alcohol, a lignin-derived model substrate, achieving over 70% conversion and >80% selectivity to benzaldehyde under atmospheric pressure and moderate temperature, with recyclability over multiple catalytic cycles while maintaining the structural integrity of the coordination framework. Kinetic and mechanistic studies, supported by radical scavenging and EPR analyses, revealed that molecular oxygen is activated in situ through Cu⁺/Cu²⁺ redox cycling, generating multiple reactive oxygen species that drive the oxidation process. This catalyst design demonstrates a sustainable route to valorize biomass under mild conditions, eliminating the need for hazardous oxidants or precious metals. The low-cost, water-processable synthesis and robust redox functionality of cyamelurate-based coordination polymers establish a versatile platform for next-generation, earth-abundant oxidation catalysts in sustainable chemical manufacturing.