Since the surfaces of the multi-walled CNTs are modified by carboxyl groups, CNTs are able to condense with the surface hydroxyl groups of titanate, as demonstrated in literatures [3,11]. Through the crosslink of CNTs, it is possible to bind the nanofibers together and form a macroscopic membrane. As we expected, an intact membrane was floated on the surface of the solution filled in the Teflon liner after the hydrothermal reaction. In parallel experiments, we did not introduce CNTs into the reaction system while keeping other conditions unchanged. Only white precipi-tates were obtained in the autoclave, suggesting that CNTs are essential for the formation of the membrane. Fig. 1a shows the XRD patterns of the membranes before and after calcination. The membrane taken out of the autoclave is composed of titanate (Fig. 1a, curve 1). After acid washing and annealing process, titanate within the membrane was transformed into monoclinic TiO2 (Fig. 1a, curve 2). The existence of CNTs in the membrane was revealed by the Raman spectroscopy characterization. Two peaks centered at 1330 cm