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

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