Templated synthesis of imine-based covalent organic framework hollow nanospheres for stable potassium-ion batteries

Covalent organic frameworks (COFs), as highly tunable porous crystalline materials, have promising applications in potassium-ion batteries (PIBs) due to their abundant charge carrier transport channels and excellent structural stability. However, the excessive stacking of interlayer electron clouds makes it difficult to expose internal active sites. Strategies to design functional COFs with controllable morphology and copious active sites are promising but still challenging. Herein, by utilizing the condensation between 1,3,5-triformylbenzene (TFB) and p-phenylenediamine (PPD) and using amino-modified SiO2 nanospheres as templates, we synthesize core-shell NH2-SiO2@TP-COF. Through NaOH etching of NH2-SiO2@TP-COF, we obtain imine-based TP-COF hollow nanospheres, which shows excellent potassium storage performance when applied to the anode for PIBs. Ex-situ analysis and density functional theory calculations reveal that CN groups and benzenes are active sites for K+ storage.