2D covalent organic framework thin films via interfacial self-polycondensation of an A 2 B 2 type monomer.

An A(2)B(2) type monomer, 1,6-bis(4-formylphenyl)-3,8-bis(4-amino-phenyl)pyrene (BFBAPy), was employed for the fabrication of continuous and highly crystalline 2D imine-linked covalent organic framework (COF) films with tunable thickness via interfacial self-polymerization. These films served as stable acidichromism sensors with rapid response, low detection limit and good repeatability.