Revealing the Mg-Ion Storage Mechanism within a Covalent Organic Framework Electrode

Magnesium batteries offer a promising alternative to lithium-ion systems, but suitable electrodes remain limited. Covalent organic frameworks (COFs) are attractive candidates due to their structural tunability and open channels for ion transport. We report a pyrene- 4,5,9,10-tetraone COF composite with carbon nanotubes as a Mg electrode, delivering 70 mAh g^-1 at 200 mA g^-1 and operating at 1.3 V. <i>In situ</i> Raman spectroscopy confirms carbonyl-centered redox on pyrene tetraone, supporting a Mg²⁺-driven carbonyl reduction. Compared with Li⁺, only partial carbonyl utilization occurs, attributed to steric and electrostatic constraints of divalent Mg²⁺. This incomplete conversion to magnesium-enolate inspires future work toward structural optimization.