Highly Ordered Nanochannels in a Nanosheet-Directed Thin Zeolite Nanofilm for Precise and Fast CO₂ Separation

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.