Pore　hierarchy　in　polymers　is　crucial　for　applications　spanning　nano-medicine,　sustainable　energy,　and　molecular　separation.　However,　polymer　free　volume　hierarchy　with　ultra-fine　sizes　(＜5　angstrom)　and　modularity　remains　an　important　but　elusive　subject　of　research　due　to　the　dynamic,　transient　and　random　nature　of　free　volume　cavities.　Here　we　show　the　construction　of　hierarchical　free　volume　through　the　self-assembly　of　structured　polyelectrolyte　complex　nanoparticles　(approximate　to　40　nm)　in　the　vacuum　filtration　process.　Membranes　with　tunable　thickness　and　well-defined　nanoparticle　structures　are　prepared,　featuring　enhanced　mechanical　strength,　flexibility,　and　more　importantly,　programmed　free　volume　consisting　of　intra-particle　(r(1)　=　3.22　angstrom)　and　inter-particle　(r(2)　=　4.45　angstrom)　cavities.　Both　free　volume　elements　are　effectively　tuned　and　the　collective　fractional　free　volume　is　improved　8　times,　leading　to　membrane　molecular　channels　outperforming　other　polymer　membranes　in　pervaporation　dehydration　of　ethanol.