Mechanical properties of organic/inorganic thin-films prepared from bridged silicon precursors have been investigated. The Young's modulus follows a linear decay when porosity is introduced, a unique observation as compared to traditional organosilicates. Remarkably, in the dense state, fracture energies of 15-17 J.m(-2) were measured, values that are larger than those for dense SiO2 (10 J.m(-2)), dispelling the common belief that all organosilicates are fragile and prone to fracture.