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

A triphosphaazatriangulene (H3L) was synthesized through an intramolecular triple phospha‐Friedel–Crafts reaction. The H3L 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 (H3L⋅0.5 [Cu2(OH)4⋅6 H2O] ⋅4 H2O), 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. Another dimension: A triphosphaazatriangulene containing three phosphinate groups and an extended π‐conjugated framework was synthesized through an intramolecular triple phospha‐Friedel–Crafts reaction. It undergoes a stimuli‐responsive reversible transformation from a 3D‐MOF that exhibits reversible sorption characteristics to a 1D‐columnar assembled proton‐conducting material.