A novel organic-inorganic hybrid titanophosphite membrane that exhibits proton conductivity at 100-150 degrees C was successfully prepared. Graded monomer conversion was achieved in the membrane by ultraviolet light (UV) absorption during polymerization: the conversion at the membrane surface was high, whereas that at the inner part was low. As a result, this membrane exhibited water durability as well as a proton conductivity of 6.3 x 10(-4) S cm(-1) at 150 degrees C under a N-2 atmosphere. This is because the inner part acted as an acidic site whereas the surface provided water resistance. Thus, the structure of the membrane with graded monomer conversion enables proton conduction under a dry atmosphere at intermediate temperatures. (C) 2012 Elsevier B.V. All rights reserved.