Zeolitic imidazolate framework-8 derived two-dimensional N-doped amorphous mesoporous carbon nanosheets for efficient capacitive deionization

Abstract

Capacitive deionization (CDI) is a promising technology to remove salt from brackish water, and the desalination efficiency depends significantly on the electrode materials with prominent electrosorption capacity. In this work, zeolitic imidazolate framework-8 (ZIF-8) derived two-dimensional (2D) N-doped amorphous mesoporous carbon nanosheets (ZMCs) were prepared via high temperature carbonization with molten salt as medium. The resultant ZMCs possessed superior specific surface area, abundant mesopores structure and high nitrogen content. Moreover, ZMCs electrodes exhibited an excellent CDI performance (46.4 mg KCl·g−1, 1.2 V) over the ZIF-8 derived carbons (ZCs) (19.1 mg g−1) prepared by direct pyrolysis without any medium. The existence of molten salt was beneficial for the formation of amorphous mesoporous carbon nanosheets during pyrolysis process. The improved capacity implied that mesoporous structure and amorphous carbon nanosheets morphology facilitated ion transportation during CDI process. Besides, ZMCs electrodes exhibited excellent regeneration stability after 15 times adsorption-desorption cycles. These results show that ZMCs would be a promising material applied in the CDI in the future.