Although organic-inorganic composite membranes have a variety of possible applications, they have a problem that they become brittle when they contain a large amount of insoluble inorganic particles , . It is because too much inorganic induces their agglomerates in a membrane when the composite is formed. As a result, it breaks from the accumulated areas of the inorganic particle when a force is applied to it . However, insoluble inorganic particles are difficult to disperse and avoid agglomeration. So then, a small amount is usually included in a membrane, although high inorganic content is ideal for fully exhibiting the properties of the inorganic. On the other hand, soluble inorganic particles can be well dispersed in organic molecules, suppress the agglomeration, and retain the membrane flexibility.