Large-Area Supramolecular Crystalline Thin Films of Polyoxometalates with Controlled 1-nm Pores Enabling Ultra-Selective Molecular Transport

Achieving angstrom-level control over porosity is a long-standing challenge in translating molecular design into selective membranes. We present the supramolecular assembly of crown-type [P 8 W 48 O 184 ] 40– polyoxometalate (POM) by alkylammonium functionalization using [C n H 2 n +1 ] 4 N +, where n = 4 (Q 4 P 8 ), 7 (Q 7 P 8 ), and 10 (Q 10 P 8 ), into continuous POM thin films ( POMbranes ) featuring periodically aligned ∼1 nm intrinsic pores (I p ) of P 8 (visualized with electron microscopy). Alkyl chain length modulations direct supramolecular packing and tune the extrinsic porosity (E p ) in POMbranes across large lateral dimensions (∼50 cm 2 ) while preserving I P . Q 7 P 8 and Q 10 P 8 POMbranes with restricted E p enforce precise sieving via I p, whereas Q 4 P 8 permits dual-path transport through I p and E p, as confirmed by cross-flow separations and molecular dynamics simulations. Q 7 P 8 and Q 10 P 8 POMbranes deliver single-digit pore selectivity (Isoporosity) and ∼10× higher separation efficiency for narrow molecular weight differences (100–200 Da) than state-of-the-art benchmark membranes, establishing a scalable strategy to embed crystalline nanopores for selective separation.