Synergistic pyrolysis and precise etching of Cu-MOF: Engineering 2D hierarchical porous carbon frameworks for ultra-fast and high-capacity capacitive deionization

The intensifying global freshwater crisis necessitates the innovation of energy-efficient and sustainable desalination technologies. Capacitive deionization (CDI) has emerged as a promising solution, yet its large-scale application is frequently hindered by suboptimal electrode architectures that limit ion storage and transport. Herein, we report a template-free, synergistic pyrolysis-etching strategy to engineer a novel 2D hierarchical porous carbon framework derived from a Cu-BDC metal-organic framework (MOF). By precisely modulating the carbonization temperature and executing in-situ acid etching to remove Cu species, the intrinsic 2D layered morphology is successfully preserved while evolving into an interconnected mesoporous network. A systematic investigation into the structural evolution reveals that the pyrolysis temperature significantly dictates the defect concentration and pore distribution. The optimized electrode, BDCE₉₀₀, achieves an exceptional salt adsorption capacity (SAC) of 58.36 mg/g and a rapid desalination rate of 3.28 mg/g/min, significantly outperforming conventional carbon counterparts. Detailed spectroscopic investigations and electrochemical kinetics analysis reveal that this superior performance stems from the high density of accessible active sites and the streamlined ion diffusion pathways facilitated by the 2D-on-2D hierarchical configuration. This work provides a scalable and robust paradigm for designing MOF-derived 2D carbon frameworks toward high-performance electrochemical water purification.