Ultralight Covalent Organic Framework/graphene Aerogels with Hierarchical Porosity

The fabrication of macroscopic architectures of covalent organic frameworks (COFs) instead of powders is of great significance to fully exploit their chemical functionality and porosity and to enable sufficient diffusion and mass transfer through the material. However, it is still a challenge to achieve the assembly of such 3D hierarchical porous architectures from COFs. Herein, COF/reduced graphene oxide (rGO) aerogels are presented, which are synthesized by a hydrothermal approach. The COFs grow in situ along the surface of the 2D graphene sheets, which are stacked in a 3D fashion, forming an aerogel after freeze-drying, which can be compressed and expanded several times without breaking. Thus, a facile, green and pyrolysis-free synthetic method for ultralight functional materials has been achieved. The COF/rGO aerogel shows excellent absorption capacity (uptake of > 200 g organic solvent/g aerogel), which can be used for removal of various organic liquids from water. Moreover, as active material of supercapacitor devices, the aerogel delivers a high capacitance of 269 F g^-1 at 0.5 A g^-1 and superior cycling stability over 5000 cycles, which is among the best results reported for COF-based supercapacitors so far. This work demonstrates a great advance for green synthesis of ultralight materials for environmental and energy applications.