Fig. 1: Structures of the monomers and the as-designed two free-standing COF membranes.

TFP, Sa, and TAPA is short for 1,3,5-triformylphloroglucinol, 2,4,6-triformylphenol, and tris(4-aminophenyl)amine, respectively. The red, blue, gray, and white spheres represent O, N, C, and H atoms, respectively.