Swelling-agent-free synthesis of mesocellular foam (MCF)-like silica mesophases by a pH-dependent structural transformation using carboxy-terminated triblock copolymer Pluronic P123 has been discovered. The structural properties of the MCF-like silica materials can be modulated by controlled calcination or post-synthesis treatment with sulfuric acid, and either closed-cell or open-cell mesostructures have been prepared. The MCF-like silica mesophases have also been applied as hard templates to prepare MCF-like carbon materials via a nanocasting route. Furthermore, the swelling-agent-free synthesis has been found to be less sensitive to the presence of organosilanes, and the cocondensation syntheses of functional MCF-like materials with carboxyethyl, iodopropyl, or mercaptopropyl groups have also been demonstrated.