A nanostructured metal oxide composition comprising hydroxides or oxygen vacancies or both hydroxides and oxygen vacancies on its surface is described. A process for preparing the nanostructured metal oxide composition comprising hydroxides or oxygen vacancies or both hydroxides and oxygen vacancies on its surface, which hydroxides and oxygen vacancies can participate in chemical reactions, which composition is prepared by a method selected from the group of methods comprising: i) controlled thermally induced dehydroxylation of nanostructured metal hydroxide precursors; ii) thermochemical reaction of said nanostructured metal oxide with hydrogen gas; iii) vacuum thermal treatment of said nanostructured metal oxide; and iv) aliovalent doping with a lower oxidation state metal. A photocatalyst comprising a nanostructured metal oxide composition comprising an optimal loading of hydroxides or oxygen vacancies or both hydroxides and oxygen vacancies on its surface, which hydroxides and/or oxygen vacancies can participate in chemical or physical reactions.