Single-atom Mn-modified biomimetic phthalocyanine covalent organic frameworks with tunable pendant groups for high-efficiency sodium chloride batteries

Rechargeable chlorine-based battery recently emerged as a promising substitute for energy storage systems due to their high average operating voltage (∼3.7 V) and large theoretical capacity of ∼754.9 mAh g -1 . However, insufficient supply of chlorine (Cl 2 ) and sluggish oxidation of NaCl to Cl 2 limit its practical application. Covalent Organic Frameworks (COFs) have the potential to be ideal Cl 2 host materials as Cl 2 adsorbents for their abundant porosity and easily modifiable nature. In this work, the single atom Mn coordinated biomimetic phthalocyanine COFs is used for Cl 2 capture and catalyst. The DFT reveals that ASMn and -NH 2 significantly change the microenvironment around the active site, effectively promote the oxidation of NaCl. When applied as the cathode material for Na-Cl 2 batteries, the SAMn-COFs-NH 2 electrode exhibits large reversible capacities and excellent high-rate cycling performances throughout 200 cycles based on the mechanism of highly reversible NaCl/Cl 2 redox reactions. Even at the temperature as low as -40 o C, the SAMn-COFs-NH 2 cathode showed stable discharge capacities at ∼1000 mAh g -1 over 50 cycles with a voltage plateau of ∼3.3 V. This work may provide new insights for the investigation of chlorine-based electrochemical redox mechanisms and the design of green nanoscaled electrodes for high-property chlorine-based batteries. The single-atom Mn-coordinated biomimetic phthalocyanine COF (SAMn-COF-NH 2 ) serves as both Cl 2 capturer and catalyst in rechargeable Na-Cl 2 batteries. The Mn-NH 2 functionalization substantially reduces the NaCl oxidation barrier and enhances reaction kinetics, enabling an ultrahigh discharge capacity of 2810 mAh g -1 with 98% Coulombic efficiency. Practical demonstrations show Na‖SAMn-COF-NH 2 pouch cells can power smartphones while maintaining 90.2% capacity retention over 50 cycles, confirming their commercial viability. • A series of new piperazine-linked COFs are prepared as Cl 2 host for Na-Cl 2 batteries, the chemically stable ACOPs has a strong Cl 2 adsorption capacity. • The ASMn and -NH 2 modified COFs significantly change the microenvironment around the active site, effectively promote the oxidation of NaCl, which improves Na + transport and enables rapid redox kinetic conversion of chlorine. • The SAMn-COFs-NH 2 contain regularly organized open channels that assist in transporting of Cl - and Na + ions, leading to fast redox kinetic conversion of NaCl. • The Na-Cl 2 batteries with SAMn-COFs-NH 2 cathode demonstrate a low overpotential and a discharge capacity of up to 996.3 mAh g -1 with a Coulombic efficiency of nearly 99.6%.