Ultraporous nitrogen-rich carbon nanosheets derived from the synergy of eutectic liquid and zeolitic imidazolate for energy applications

Reported here is a unique and novel synthetic method for the preparation of highly porous nitrogen-rich carbon nanosheets from ZIF-8 (ZIF, zeolitic imidazolate framework) with the assistance of eutectic liquid. Due to the low melting temperature, a mixture of eutectic salts can provide a special atmosphere for the carbonization process and function as the template to support the ZIF-8 framework. The formation of the ultraporous nanosheets can be ascribed to the excellent miscibility between the eutectic salts and ZIF-8 framework, thus helping convert the ordered calcined intermediate species into extended carbon sheets at high temperature while inheriting the microporous structure from the prototypical ZIF-8. By controlling the ratio of eutectic liquid to ZIF-8 framework, the BET surface area of carbon nanosheets can be systematically tuned, with the highest BET surface area up to 2960 m2 g−1. In addition to this impressive high surface area, the pore size distribution follows well with the pristine ZIF-8. The nitrogen content varies from 9.9 wt % to 13.4 wt %. These characteristics contribute to the excellent performance of CO2 adsorption (5.45 mmol g−1 at 1atm and 273K) and oxygen reduction reaction (ORR) catalysis due to the large numbers of accessible active sites.