Lithium　metal　batteries　(LMBs)　have　garnered　considerable　interest　because　of　their　substantial　theoretical　capacity.　However,　their　development　is　hampered　due　to　the　grave　issue　of　hazardous　lithium　dendrites　arising　from　inhomogeneous　lithium　(Li)　electrodeposition.　An　effective　strategy　for　addressing　dendritic　growth　is　to　regulate　the　migration　behavior　of　target　molecules　and/or　ions　during　cycling.　Herein,　we　demonstrate　an　in　situ　self-assembly　strategy　where　metal-organic　frameworks　(MOFs)　grow　on　a　polypropylene　separator　homogeneously　along　a　certain　orientation.　By　integration　of　abundant　functional　groups　and　secondary　structural　units,　a　continuous,　uniform,　and　defect-free　distribution　of　MOFs　on　the　substrate　membrane　was　achieved.　The　intrinsic　subnanochannels　of　MOFs　significantly　benefit　the　transfer　of　Li+　ions　and　restrain　the　chaotic　movement　of　target　ions,　resulting　in　a　high　Li+　migration　number　(0.86)　and　enhanced　Li+　ionic　conductivity.　Consequently,　a　highly　stable　lithium　plating/stripping　behavior　was　observed,　leading　to　efficacious　lithium　deposition　and　stable　cycling　over　1200　h　at　2　mAh　cm-2.　Additionally,　the　permselective　MOF-based　separator　with　tunable　channel　sizes　promises　broad　applicability　in　LMBs.　Our　approach　paves　a　new　pathway　for　in　situ　self-assembly　strategies　for　permselective　MOF-based　separators,　which　is　expected　to　help　develop　advanced　LMBs　with　high　energy　density　and　long-life　performance.　©　2024　American　Chemical　Society.