A multicomponent donor-π-acceptor covalent organic framework as a nanoporous cation-selective separator for durable aqueous zinc ion batteries

A zinc metal anode shows promise as a candidate material for high-performance zinc-based batteries due to its high safety and low cost. However, the rampant growth of zinc dendrites and occurrence of side reactions pose challenges for practical applications. Herein, a promising strategy of modifying the glass fiber (GF) separator by the introduction of a porous covalent organic framework (COF) with an alternating electron donor-pi-acceptor structure is designed to guide selective and uniform zinc cation transport and deposition. Theoretical calculations and various in/ex situ experiments demonstrate that triazine-based groups are used as the electron acceptor with a negative charge and can guide the rapid directional migration of zinc ions. Thieno [3,2-b]thiophene groups function as the electron donor with a positive charge and can anchor anions and inhibit the occurrence of side reactions. The electron acceptor and donor structures are linked by pi-conjugated benzene rings and imine linkages, facilitating electron delocalization and stabilization. Moreover, N-containing zincophilic organic groups in the porous COF structure contribute to the uniform transport and deposition of zinc ions. The symmetric cells with the modified GF separator can work stably for more than 1200 h and the corresponding Zn & Vert;MnO2 full cell delivers a large reversible capacity of 138.7 mA h g-1 after cycling for 1000 cycles at 1 A g-1. The design of this covalent organic framework separator offers new insights into the development of high-performance zinc-ion batteries.