Electrospun　nanofibrous　air-filtration　membranes,　which　are　cost-effective　materials　that　help　safeguard　human　health,　have　garnered　widespread　attention.　To　comprehensively　enhance　the　protection　capabilities,　comfort　(for　masks),　energy　efficiency　(for　air　purifiers),　and　achieve　optimal　overall　benefits,　there　is　a　demand　for　the　functionalization　and　lightweighting　of　high-performance　air　filtration　membranes.　Bimodal　nanofiber　membranes　can　deliver　high-performance　air　filtration　with　a　higher　proportion　of　fine　fibers,　contributing　to　a　lightweight　design.　Moreover,　they　are　compatible　with　various　functionalization　strategies.　Therefore,　an　in-depth　analysis　of　electrospun　bimodal　nanofibrous　membranes　is　key　to　promoting　the　development　of　high-performance　air　filters.　However,　this　has　yet　to　be　achieved.　Importantly,　deep-level　mechanisms　of　the　electrospun　jet　behavior　are　involved　in　the　fabrication　of　bimodal　structures.　Reflection　on　these　phenomena　may　guide　theoretical　and　experimental　studies　in　related　fields,　such　as　fluid　dynamics　and　materials　science.　This　study　details　electrospun　bimodal　nanofibrous　membrane　properties,　high-performance　air　filtration　mechanisms,　fabrication　methods,　and　molding　mechanisms.　Subsequently,　the　functionalized　applications　are　summarized.　Finally,　the　challenges　encountered　in　the　development　of　bimodal　air　filtration　membranes　are　discussed.　©　2024　Elsevier　B.V.