Aerogels, an extremely important aggregation state of various self-assembled nanoscale building blocks, have great potential in fields ranging from energy storage to thermal insulation. However, the porosity of aerogels makes them mechanically weak in most cases, and the chemical activity of the resulting aerogel needs consideration. Herein, chemically crosslinked graphene oxide (GO) 3D aerogels with large specific surface areas (up to 850 m2 g−1), outstanding mechanical performance (up to 20 MPa Young's modulus, 1 MPa yield strength and 45 J g−1 specific energy adsorption), and superhigh chemical activity (toward some reducing gases such as H2S, HI, and SO2), are fabricated by assembling 2D GO sheets edge-to-edge into uniform, 3D hydrogel networks with subsequent supercritical fluid drying. These aerogels are superior to other 3D frameworks (e.g. graphene aerogels) assembled via partial overlapping of the basal planes of the 2D building blocks.