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 [CnH2n+1]4N+, where n = 4 (Q4P8), 7 (Q7P8), and 10 (Q10P8), into continuous POM thin films (POMbranes) featuring periodically aligned ∼1 nm intrinsic pores (Ip) of P8 (visualized with electron microscopy). Alkyl chain length modulations direct supramolecular packing and tune the extrinsic porosity (Ep) in POMbranes across large lateral dimensions (∼50 cm2) while preserving IP. Q7P8 and Q10P8 POMbranes with restricted Ep enforce precise sieving via Ip, whereas Q4P8 permits dual-path transport through Ip and Ep, 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.实现孔隙的埃级精准调控，是将分子设计转化为选择性分离膜领域长期存在的核心挑战。本研究采用[CnH2n+1]4N+（其中n=4对应Q4P8、n=7对应Q7P8、n=10对应Q10P8）进行烷基铵功能化，成功实现冠型结构[P8W48O184]40–多金属氧酸盐（polyoxometalate, POM）的超分子组装，制备得到连续的POM薄膜（POMbranes）。该薄膜具有P8结构单元的周期性排列~1 nm固有孔隙（intrinsic pores, Ip），经电子显微镜可视化表征。烷基链长度的调控可引导超分子堆积方式，并在POM膜的大横向尺寸（~50 cm²）范围内调节其外在孔隙（extrinsic porosity, Ep），同时保留固有孔隙（Ip）结构。Q7P8与Q10P8型POM膜的外在孔隙（Ep）受限于狭窄区间，可通过固有孔隙（Ip）实现精准筛分；而Q4P8型POM膜则可通过固有孔隙（Ip）与外在孔隙（Ep）实现双路径传输，该结论经错流分离实验与分子动力学模拟验证。相较于当前主流的基准分离膜，Q7P8与Q10P8型POM膜可实现单级孔隙选择性（Isoporosity），且对于分子量差为100–200 Da的窄分布溶质，分离效率提升约10倍，由此确立了一种可规模化嵌入结晶纳米孔隙以实现选择性分离的策略。