In a compression experiment on a nanoporous silica gel, it is observed that at a high pressure the collapse of nanoporous structure provides a mechanism for plastic deformation, leading to an energy absorption efficiency much higher than that of many conventional protection and damping materials. Even though the network material is brittle, the overall behavior of the silica gel is ductile. After the compression test, the nanopore volume is largely reduced while the variation in nanopore surface area is secondary. According to a first-order poromechanic analysis, the effective plastic deformation is dominated by the buckling of the nanopore walls parallel to the external loading.