Solvent Dependent Structures of Melamine: Porous or Nonporous?

Two hydrogen-bonded organic frameworks
(HOFs) of the melamine (MA), MA-1-H2O and MA-2-DMF, have been crystallized
in H2O and DMF (N,N-Dimethylformamide),
respectively. Structurally, MA-1-H2O and MA-2-DMF are condensed and
porous, respectively. The porous MA-2-DMF sustains the
porous feature under the solvent exchange by acetone, dichloromethane
(CH2Cl2), and toluene, while it transforms into
the condensed one under methanol (MeOH) and ethanol (EtOH). Furthermore, MA-2-DMF and MA-2-Toluene can undergo reversible
single crystal–single crystal transformation with retention
of the porous hydrogen-bonded organic frameworks.