Investigating the Effect of Positional Isomerism on the Assembly of Zirconium Phosphonates Based on Tritopic Linkers

Abstract

We report on the use of a novel tritopic phosphonic linker, 2,4,6-tris[3-(phosphonomethyl)phenyl]-1,3,5-triazine, for the synthesis of a layered zirconium phosphonate, named UPG-2. Comparison with the structure of the permanently porous UPG-1, based on the related linker 2,4,6-tris[4-(phosphonomethyl)phenyl]-1,3,5-triazine, reveals that positional isomerism disrupts the porous architecture in UPG-2 by preventing the formation of infinitely extended chains connected through Zr-O-P-O-Zr bonds. The presence of free, acidic P-OH groups and an extended network of hydrogen bonds makes UPG-2 a good proton conductor, reaching values as high as 5.7x10<sup>-4</sup> S cm<sup>-1</sup>.<br>

Proton Conductive Zr-Phosphonate UPG-1—Aminoacid Insertion as Proton Carrier Stabilizer

“…However, both solids exhibit similar proton conductivities (around 10 −4 S·cm −1 ) at high temperature, indicating the poor impact of the Lys encapsulation on the final conductivity values. Note here that these values are in the range of the reported ones for other phosphonate-based MOFs ( Table S1 ), including the recently reported UPG-2 (10 −4 S·cm −1 ) [ 41 ] which is based on an isomeric H 6 ttbmp linker and presents an identical chemical formula than UPG-1.…”