A Nanoring-Like Superstructure of N, P-Doped Carbons Derived from Mof@Mof for High-Performance Capacitive Deionization

The developments of efficient carbonaceous materials are of significant importance to break through the bottlenecks of limited desalination capacities, slow salt adsorption rates, and poor cycling stabilities of the traditional electrodes for capacitive deionization (CDI). Herein, we reported a simultaneous MOF-on-MOF growth combined with the MOF-etching strategy for the tailoring of MOF@MOF heterostructure. Afterwards, a nanoring-like superstructure of N, P co-doped carbon rings (NPC-Rings) was synthesized through the thermal transformation of MOF@MOF precursors and followed by the phosphidation activation. Taking advantages of such hierarchically porous superstructures, the NPC-Rings exhibited efficient electrodes for CDI with high adsorption capacity, fast salt adsorption rate, and superior cycling stability. Finite element simulations further revealed that the unique superstructure of the NPC-Rings considerably promotes the current density and generates charge migration, thereby provides stronger salt adsorption capacity.