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.