Metal-coordinated sub-10 nm membranes for water purification

Ultrathin membranes with potentially high permeability are urgently demanded in water purification. However, their facile, controllable fabrication remains a grand challenge. Herein, we demonstrate a metal-coordinated approach towards defect-free and robust membranes with sub-10 nm thickness. Phytic acid, a natural strong electron donor, is assembled with metal ion-based electron acceptors to fabricate metal-organophosphate membranes (MOPMs) in aqueous solution. Metal ions with higher binding energy or ionization potential such as Fe(3+) and Zr(4+) can generate defect-free structure while MOPM-Fe(3+) with superhydrophilicity is preferred. The membrane thickness is minimized to 8 nm by varying the ligand concentration and the pore structure of MOPM-Fe(3+) is regulated by varying the Fe(3+) content. The membrane with optimized MOPM-Fe(3+) composition exhibits prominent water permeance (109.8 L m(−2) h(−1) bar(−1)) with dye rejections above 95% and superior stability. This strong-coordination assembly may enlighten the development of ultrathin high-performance membranes.