Methods of increasing the solubility of a base in supercritical carbon dioxide include forming a complex of a Lewis acid and the base, and dissolving the complex in supercritical carbon dioxide. The Lewis acid is soluble in supercritical carbon dioxide, and the base is substantially insoluble in supercritical carbon dioxide. Methods for increasing the solubility of water in supercritical carbon dioxide include dissolving an acid or a base in supercritical carbon dioxide to form a solution and dissolving water in the solution. The acid or the base is formulated to interact with water to solubilize the water in the supercritical carbon dioxide. Some compositions include supercritical carbon dioxide, a hydrolysable metallic compound, and at least one of an acid and a base. Some compositions include an alkoxide and at least one of an acid and a base.