Atomic–Level Interfacial Regulation Enables Efficient Chlorine Redox Chemistry in Rechargeable H 2 ─Cl 2 Batteries

ABSTRACT Hydrogen─chlorine (H 2 ─Cl 2 ) batteries are attractive high‐power energy storage systems but remain fundamentally limited by inefficient Cl 2 confinement and sluggish interfacial Cl 2 /Cl − redox kinetics. Here, we report a hydrogen‐bonded porphyrin framework with atomically dispersed Cu sites (SACu‐GTUB5) that enables efficient Cl 2 storage and accelerates Cl 2 /Cl − conversion. The intrinsic porosity of the framework combined with chemically active Cu─N 4 centers enables synergistic physical confinement and chemical adsorption of Cl 2 , effectively suppressing Cl 2 escape and improving Coulombic efficiency. As a result, the SACu‐GTUB5‐based H 2 ─Cl 2 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─N 4 sites govern Cl 2 adsorption, electron redistribution, and reaction pathways, substantially lowering the energy barriers for Cl 2 reduction. This work establishes an atomic‐level interfacial regulation strategy for controlling halogen redox chemistry in electrochemical energy storage.