Ion selective membrane is an essential element in energy and environmental fields such as flow batteries or Lithium ion extraction. Like all membranes, the ion selective membrane has a trade off between permeability and conductivity. To overcome this trade-off, we produce a siloxane based membrane with a proper pore size about few angstroms. Siloxane matrix with proper pore size can play the role of a sieving effect, only allowing some molecules through while blocking others. At the same time, a membrane with an ultra-thin thickness is designed to decrease membrane resistance. In this research, ultra-thin siloxane matrix can be created through the sol gel reaction of silicon alkoxide at the liquid liquid interface using total wetting phenomena. The ultra thin siloxane based matrix can be introduced onto support porous membrane to form a thin film composite. For using vanadium redox flow battery, we checked vanadium permeability and proton conductivity.