Hybrid 2D-2D materials composed of perpendicularly oriented covalent organic frameworks (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 has a forest of COF-1 nanosheets with a thickness of 3 to 15 nm in edge-on orientation relative to GO. The reaction performed without molecular pillars resulted in uncontrollable growth of thick COF-1 platelets parallel to the surface of GO. The v-COF-GO was converted into a conductive carbon material preserving the nanostructure of precursor with ultrathin porous carbon nanosheets grafted to graphene in edge-on orientation. It was demonstrated as a 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.
Activated reduced graphene oxide (a-rGO) is a material with a rigid 3D porous structure and high specific surface area (SSA). Using variation of activation parameters and post-synthesis mechanical treatment we prepared two sets of materials with a broad range of BET (N 2 ) SSA B1000-3000 m 2 g À1 , and significant differences in pore size distribution and oxygen content. The performance of activated graphene as an electrode in a supercapacitor with KOH electrolyte was correlated with the structural parameters of the materials and water sorption properties. a-rGO is a hydrophobic material as evidenced by the negligibly small BET (H 2 O) SSA determined using analysis of water vapor sorption isotherms. However, the total pore volume determined using water vapor sorption and sorption of liquid water is almost the same as the one found by analysis of nitrogen sorption isotherms. Ball milling is found to provide an improved bulk density of activated graphene and collapse of all pores except the smallest ones (o2 nm). A decrease in the activation temperature from 850 1C to 550 1C is found to result in materials with a narrow micropore size distribution and increased oxygen content. Elimination of mesopores using ball milling or a lower activation temperature provided materials with better specific capacitance despite a significant decrease (by B30%) of the BET (N 2 ) SSA. The best gravimetric and volumetric capacitances in KOH electrolyte were achieved not for samples with the highest value of the BET (N 2 ) SSA but for materials with 80-90% of the total pore volume in micropores and an increased BET (H 2 O) SSA. Comparing the performance of electrodes prepared using rGO and a-rGO shows that a more hydrophilic surface is favorable for charge storage in supercapacitors with KOH electrolyte. Fig. 14 Electrochemical analyses of rGO and a-rGO materials activated at 550 1C, 600 1C and 850 1C: (a) CV curves recorded at 50 mV s À1 . (b) Charge/discharge curves recorded at a 1 A g À1 current density.
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