Thiazole-conjugated covalent organic framework membranes enable ultraselective molecular desalination under strongly acidic conditions

Membrane nanofiltration provides a sustainable and energy-efficient platform for precise molecular separation. However, highly permselective and chemically stable membrane materials capable of operating under harsh conditions are currently lacking. Here we report a generalizable monomer–solvent dual engineering strategy that enables the one-step synthesis of chemically robust thiazole-linked polycrystalline covalent organic framework (COF) membranes via scalable interfacial polymerization under ambient conditions for ultraselective molecular separation. The fully π-conjugated aromatic skeleton and the spatially exposed heteroatoms on the irreversible thiazole linkages establish a lone-pair electron network, which not only forms an atomic hydration layer to protect the framework but also confers long-range regulation of electrostatic interactions. The thiazole-linked COF membranes exhibit remarkable structural stability in strong acids (e.g., 12 M HCl), good resistance to organic solvents and chlorine, and high pharmaceutical desalination permselectivity, achieving ion/pharmaceutical separation factors up to 690. This versatile thiazole-linked framework structure offers potential for the development of chemically stable aromatic conjugated COF membranes for diverse vital applications. Permselective and chemically stable membrane materials for molecular separation operating under harsh conditions are currently lacking. Here, the authors report a monomer–solvent dual engineering strategy that enables the synthesis of chemically robust thiazole linked polycrystalline covalent organic framework membranes via scalable for selective molecular separation.