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.