Tailoring the Electrochemical Responses of MOF-74 Via Dual-Defect Engineering for Superior Energy Storage.

Rationally designed defects in a crystal can confer unique properties. This study showcases a novel dual-defects engineering strategy to tailor the electrochemical response of metal-organic framework (MOF) materials used for electrochemical energy storage. Salicylic acid (SA) is identified as an effective modulator to control MOF-74 growth and induce structural defects, and cobalt cation doping is adopted for introducing a second type of defect. The resulting dual-defects engineered bimetallic MOF exhibits a discharging capacity of 218.6 mAh g -1 , 4.4 times that of the pristine MOF-74, and significantly improved cycling stability. Moreover, the engineered MOF-74(Ni 0.675 Co 0.325 )-8//Zn aqueous battery shows top energy/power density performances for Ni-Zn batteries (266.5 Wh kg -1 , 17.22 kW kg -1 ). Comprehensive investigations reveal that engineered defects modify the local coordination environment and promote the in situ electrochemical reconfiguration during operation to significantly boost the electrochemical activity. This work suggests that rational tailoring of the defects within the MOF crystal is an effective strategy to manipulate the coordination environment of the metal centers and the corresponding electrochemical reconfiguration for electrochemical applications.