A　defect-free,　robust　and　selective　barrier　is　essential　for　manufacturing　membranes　with　targeted　high　permeability　and　selectivity.　Here　we　report　a　new　route　to　engineering　a　separation　composite　membrane　by　confining　both　channels　in　nanoscale　metal　organic　frameworks　(MOFs)　and　charges　in　a　polyelectrolyte　in　the　inner　space　of　a　porous　supportviaa　counter-diffusion　method.　A　simple　thermal　annealing　treatment　of　the　interface　between　the　MOF,　polymer　and　support　favorably　reduced　voids　inside　this　nano-confinement　environment.　As　this　composite　membrane　combines　both　the　support　and　barrier　as　one,　it　minimizes　mass　transfer　resistance　of　water　molecules.　In　a　separation　test,　it　readily　achieved　the　state-of-the-art　permeance.　This　simple　chemical　approach　to　upgrade　membrane　structures　will　offer　wide　opportunities　in　separation　devices.