Monodispersed covalent organic framework nanocrystals in aqueous solution for DNA inclusion

Covalent organic framework (COF) nanocrystals are useful in biological applications; however, their hydrophobic nature makes them aggregate into clusters in aqueous media. In this work, we show that by modifying the crystal surface with hydrophilic functional groups, these nanocrystals can maintain in the monodispersed form in aqueous solution. Specifically, three COFs, TPB-DMTP COF, TAPB-PDA COF and TAPB-BPDA COF were synthesized using organic Lewis acid as the catalyst, to generate nanoparticles with the size ranging from 180 nm to 1 µm. 2-Aminoethanesulfonic acid (AESA) was applied to react with the terminal aldehyde functional groups exposed at the surface of COF nanocrystals. The resulting negatively charged surface keeps these nanocrystals apart from each other in aqueous solution for at least 48 h. The mesopore of these COF nanocrystals allows the entering of single-strand DNA molecules and the release in the presence of complementary DNA. [graphic not available: see fulltext]