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 high thermal stability maintaining its crystallinity and structural features up to ca. 800 °C, thus being to date the most thermally-robust and stable MOF. This remarkable feature is attributed to the close compact 3D network maintained by the strong pyrophosphonate bridges formed by the dehydration of the material at high temperatures.