Postsynthetic modification of an imine-based microporous organic network

A highly cross-linked microporous organic network with imine linkers was prepared by condensation of tetrakis(4-aminophenyl)methane with terephthaldehyde. Gas adsorption studies indicate that the material exhibits permanent microporosity, and guest exchange experiments demonstrate that small molecules can diffuse into the network. Postsynthetic modification of this microporous network was achieved by treatment with borane in THF, which reduced the imine groups to the corresponding amines as shown by IR and 13C CP-MAS solid-state NMR spectroscopy. The resulting material showed enhanced resistance to acidic hydrolysis compared with the imine precursor, and retained its ability to absorb guest molecules. The amine network was amenable to further postsynthetic modifications. Specifically, acetylation of this network using acetic anhydride was demonstrated.