Recently　B←N　organic　frameworks　(BNFs)　have　gained　substantial　attention　owing　to　their　unique　dative　bond　energy,　which　imparts　them　with　specialized　functionalities　across　a　broad　spectrum　of　applications.　Despite　previous　reports　on　BNFs　with　permanent　porosity,　research　endeavors　towards　three-dimensional　(3D)　BNFs　with　similar　properties　are　scarce,　with　no　report　of　robust　3D　BNFs　featuring　permanent　porosity　to　date.　Herein,　electrostatic　complementary　strategy　is　proposed　to　construct　the　first　example　of　3D　robust　and　microporous　BNF,　BNF-100,　featuring　a　reo　topology　with　8-connected　sandwich　nodes　assembled　via　dative　B←N　bonds.　The　activated　form　BNF-100　a　exhibits　excellent　chemical　stability　and　permanent　porosity　with　Langmuir　surface　area　of　645.9　m2　g−1　and　pore　volume　of　0.23　cm3　g−1.　BNF-100　a　can　efficiently　separate　hexane　isomers　through　sieving　mechanisms,　as　confirmed　by　vapor　adsorption　experiments　and　dynamic　breakthrough　tests,　surpassing　the　performance　of　most　MOF　materials.　Finally,　we　achieved　the　purification　of　different　branched　hexane　isomers　using　a　single　breakthrough　column　in　a　combined　breakthrough　and　purging　experiment,　which　is　the　first　reported　instance　in　the　literature　on　hexane　isomer　separation.　©　2024　Wiley-VCH　GmbH.