Aerogels are widely applied for construction, aerospace, military, and energy owing to their lightweight, high specific surface area, and high porosity. The high porosity of aerogels often leads to a lack of mechanical strength, which limits their applications. Here, this study reports a mechanically robust MXene/cellulose nanocrystal composite aerogel enabled by inducing dense bridging through salting-out. First, MXene sheets are bridged with cellulose molecular chains via hydrogen bonds, and further dense bridging is constructed by promoting hydrogen bond formation through salting-out. By enhancing hydrogen bonding, the interlayer spacing of MXene sheets is reduced and their orientation is improved, effectively increasing the energy dissipation capacity of the porous structure. The aerogel exhibits a Young’s modulus of 72.4 MPa, a specific modulus of 342.0 kN m/kg. An aerogel is used as a triboelectric material to construct a highly robust triboelectric nanogenerator. This study provides an effective strategy for the preparation of the mechanically robust aerogels.