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 [P₈W₄₈O₁₈₄]^40- polyoxometalate (POM) by alkylammonium functionalization using [C_nH_2n+1]₄N⁺, where n = 4 (Q₄P₈), 7 (Q₇P₈), and 10 (Q₁₀P₈), into continuous POM thin films (POMbranes) featuring periodically aligned ∼1 nm intrinsic pores (I_p) of P₈ (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 cm²) while preserving I_P. Q₇P₈ and Q₁₀P₈ POMbranes with restricted E_p enforce precise sieving via I_p, whereas Q₄P₈ permits dual-path transport through I_p and E_p, as confirmed by cross-flow separations and molecular dynamics simulations. Q₇P₈ and Q₁₀P₈ 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.