Precise molecular and ion separations depend largely on the size and uniformity of the nanochannels in a defect‐free microporous nanofilm. Ordered and perpendicular nanochannels with uniform pore size are assembled into a continuous and defect‐free film by a “gel nuclei‐less” route. The ultrathin (<50 nm) zeolite nanosheets seeding layer induces the formation of defect‐free zeolite nanofilms (500–800 nm) with preferential [100] orientation well‐aligned to the transport pathway. The large‐area and thin silicoaluminophosphate‐34 (SAPO‐34) nanofilm consisting of uniform and straight nanochannels shows a milestone CO2 permeance of ≈1.0 × 10−5 mol (m2 s Pa)−1 and high CO2/CH4 and CO2/N2 selectivities of 135 and 41 in equimolar binary mixtures at room temperature and 0.2 MPa feed pressure, respectively. These results suggest that highly oriented and thin SAPO‐34 nanofilms prepared from nanosheets might have great potential for CO2 capture from natural gas, biogas, and flue gas.