Solvent-Vapor-Induced Reversible Single-Crystal-to-Single-Crystal Transformation of a Triphosphaazatriangulene-Based Metal-Organic Framework.

A triphosphaazatriangulene (H3 L) was synthesized through an intramolecular triple phospha-Friedel-Crafts reaction. The H3 L triangulene contains three phosphinate groups and an extended π-conjugated framework, which enables the stimuli-responsive reversible transformation of [Cu(HL)(DMSO)⋅(MeOH)]n , a 3D-MOF that exhibits reversible sorption characteristics, into (H3 L⋅0.5 [Cu2 (OH)4 ⋅6 H2 O] ⋅4 H2 O), a 1D-columnar assembled proton-conducting material. The hydrophilic nature of the latter resulted in a proton conductivity of 5.5×10-3  S cm-1 at 95 % relative humidity and 60 °C.