Exceptional Thermal Stability of Lanthanide-Phosphonate Frameworks

Abstract

A single-crystal-to-single-crystal transformation (SC-SC) of [Ln(H5btp)]∙2H2O [where Ln3+ = Gd3+ (1Gd), Tb3+ (1Tb), Dy3+ (1Dy), Ho3+ (1Ho), Er3+ (1Er), and Tm3+ (1Tm)] led to the formation of [Ln(L)(HL)] (where L = [–(PO3)(C6H3)(PO2)] and HL = [–(PO2H)(C6H3)(PO2)]n) based on a polymeric phosphonate-based organic linker (i.e., a polyMOF). The resulting material has a high thermal stability maintaining its crystallinity and structural features up to ca. 800 ºC, thus being to date the most thermally-robust and stable MOF. This remarkable feature is attributed to the close compact 3D network maintained, especially by the strong pyrophosphonate bridges formed by the dehydration of the material at high temperatures.