Molecular pillar approach to grow vertical covalent organic framework nanosheets on graphene: new hybrid materials for energy storage

Hybrid 2D-2D materials composed by perpendicularly oriented covalent organic framework (COFs) and graphene were prepared and tested for energy storage applications. Diboronic acid molecules covalently attached to graphene oxide (GO) were used as nucleation sites for directing vertical growth of COF-1 nanosheets (v-COF-GO). The hybrid material shows forest of COF-1 nanosheets with thickness of ~3 to 15 nm in edge-on orientation relative to GO. The same reaction performed in absence of molecular pillars resulted in uncontrollable growth of thick COF-1 platelets parallel to the surface of GO. The v-COF-GO was converted into conductive carbon material preserving the nanostructure of precursor with ultrathin porous carbon nanosheets grafted to graphene in edge-on orientation. It was demonstrated as high-performance electrode material for supercapacitors. The molecular pillar approach can be used for preparation of many other 2D-2D materials with control of their relative orientation.