Crystallization of an amorphous inorganic network of mesoporous metal oxides is achieved while maintaining the original ordered mesoporous structure. The methodology utilizes reinforcement (carbon or silica) to strengthen the periodic structure so that the original ordered mesoporous structure is preserved during thermal treatment for crystallization. The reinforcement is removed after crystallization to provide crystalline mesoporous metal oxide with the original ordered structure. Enhancement of photocatalytic activity for the total decomposition of water over mesoporous Ta2O5 after crystallization is shown as an example of the advantages of crystalline mesoporous metal oxides.