Layer defoliation and slippery of triformylphloroglucinol-covalent organic framework under pH stress

The triformylphloroglucinol covalent organic framework is a keto-enamine-based porous matrix generally presented as two-dimensional layers stacked to form a superstructure. This study aims to compare the layer stability for three Tp-COFs, two from triformylphloroglucinol and compounds containing the 2,5-diamino structure, TpPa(OH)₂ and TpPaSO₃Na, and another from triformylphloroglucinol and biuret, called TpBu. The pH −0.2 stresses moderately slip the TpPa(OH)₂ layers, while pH 14 stress leads to severe layer slippery to deteriorate its long-range crystal structure. The excess protons protonate the sulfite group of TpPaSO₃Na, weaken the H bonds between amine and S-O groups, and make the pH −0.2 stress layer slippery. The layer stability of Tp-COFs correlates with the H bonds formed with the amine groups. The TpBu has excessive amine groups, hence having the highest layer stability.