Atomic-Level Interfacial Regulation Enables Efficient Chlorine Redox Chemistry in Rechargeable H2─Cl2 Batteries.

Hydrogen─chlorine (H2─Cl2) batteries are attractive high-power energy storage systems but remain fundamentally limited by inefficient Cl2 confinement and sluggish interfacial Cl2/Cl- redox kinetics. Here, we report a hydrogen-bonded porphyrin framework with atomically dispersed Cu sites (SACu-GTUB5) that enables efficient Cl2 storage and accelerates Cl2/Cl- conversion. The intrinsic porosity of the framework combined with chemically active Cu─N4 centers enables synergistic physical confinement and chemical adsorption of Cl2, effectively suppressing Cl2 escape and improving Coulombic efficiency. As a result, the SACu-GTUB5-based H2─Cl2 battery exhibits stable operation across a wide temperature range (-40°C to 60°C) and achieves a high areal discharge capacity of 2.55 mAh cm-2 over 300 cycles. Spectroscopic analyses combined with density functional theory calculations reveal that Cu─N4 sites govern Cl2 adsorption, electron redistribution, and reaction pathways, substantially lowering the energy barriers for Cl2 reduction. This work establishes an atomic-level interfacial regulation strategy for controlling halogen redox chemistry in electrochemical energy storage.