Effective air filtration proposed for fibers requires their assembly into a porous structure with small pore size, low packing density, and controllable macro-structure; however, creating such filtration media has proved to be a grand challenge. Here, we introduce a strategy to create microwave structured polyamide-6/poly(m-phenylene isophthalamide) nanofiber/net (PA-6/PMIA NFN) membranes for effective air filtration by combining the electro-spinning/netting (ESN) and staple fiber intercalating process. Our approach causes the PA-6 NFN membrane composed of one-dimensional (1D) nanofibers and 2D Steiner-tree nanonets, and the embedded PMIA staple fibers, to assemble into a stable filtration medium with tunable pore size, packing density, and microwave fluctuation by facilely optimizing binary fiber construction and extrinsic staple fiber intercalation. By virtue of the integrated structural properties of small pore size (similar to 0.32 mu m), high porosity (91.3%), and extended surface area, the resulting PA-6/PMIA NFN filter can effectively filter ultrafine airborne particles, mainly using physical sieving, with high filtration efficiency of 99.995%, low pressure drop of 101 Pa, desirable quality factor of 0.1 Pa-1, and large dust-holding capacity of >50 g m(-2), which match well with the requirements for treating the real particulate matter (PM) pollutions. This work would not only provide great potential for PM2.5 governance, but also open new avenues for the design and development of stable porous membranes with controllable macrostructures for various applications.