High-quality graphene sheets decorated with ZIF-8 nanocrystals

Abstract Excellent-quality graphene sheets produced via the direct liquid phase exfoliation of highly crystalline graphite (avoiding any oxidative treatment), were employed for the first time as 2D scaffolds for the in-situ synthesis of zeolitic-imidazolate-framework (ZIF-8) material. Our synthetic approach involved the efficient, urea-assisted exfoliation of natural graphite (without using any acids), and the subsequent selective, mild functionalization of the resulting high-quality graphene sheets with benzoic acid functional groups. The graphene derivatives were next decorated via the in-situ development of ultrasmall (approx. 30 nm) ZIF-8 nanocrystals. We discuss the critical role of the functionalized graphene to the selective nucleation and crystal growth of ZIF-8 nanocrystals exclusively at their surface. In-depth gas sorption studies of different gases revealed that the novel ZIF-8@Graph nano-composites exhibited improved porosity (in terms of surface area and pore volume) compared to analogous Graphene Oxide/ZIF-8 hybrids. In addition, the gate effect of the ZIF-8 nanocrystals anchored onto the high-quality graphene, was found very different compared to bulk ZIF-8, a behavior that is attributed mainly to the significantly smaller crystal size and the perfect 2D confinement of ZIF-8 along graphene. Finally, preliminary CO2 adsorption properties of the synthesized novel nano-composites are reported, at near ambient temperature.