From light to heavy alkali metal tetraphosphonates (M = Li, Na, K, Rb, Cs): cation size-induced structural diversity and water-facilitated proton conductivity

A family of alkali metal-based frameworks containing the tetraphosphonate linker hexamethylenediamine-N,N,N′,N′-tetrakis(methylenephosphonic acid), HDTMP, exhibiting rich structural diversity and water-dependent proton conductivity.