Mixed　matrix　membranes　(MMMs),　conjugating　the　advantages　of　flexible　processing-ability　of　polymers　and　high-speed　mass　transfer　of　porous　fillers,　are　recognized　as　the　next-generation　high-performance　CO2　capture　membranes　for　solving　the　current　global　climate　challenge.　However,　controlling　the　crystallization　of　porous　metal-organic　frameworks　(MOFs)　and　thus　the　close　stacking　of　MOF　nanocrystals　in　the　confined　polymer　matrix　is　still　undoable,　which　thus　cannot　fully　utilize　the　superior　transport　attribute　of　MOF　channels.　In　this　study,　the　＂confined　swelling　coupled　solvent-controlled　crystallization＂　strategy　is　employed　for　well-tailoring　the　in-situ　crystallization　of　MOF　nanocrystals,　realizing　rapid　(＜5　min)　construction　of　defect-free　freeway　channels　for　CO2　transportation　in　MMMs　due　to　the　close　stacking　of　MOF　nanocrystals.　Consequently,　the　fabricated　MMMs　exhibit　approximately　fourfold　enhancement　in　CO2　permeability,　i.e.,　2490　Barrer　with　a　CO2/N-2　selectivity　of　37,　distinctive　antiplasticization　merit,　as　well　as　long-term　running　stability,　which　is　at　top-tier　level,　enabling　the　large-scale　manufacture　of　high-performance　MMMs　for　gas　separation.