Abstract

In this paper we report on synthesis and characterisation of the first phosphonate and phosphonic acid-modified porous silicas and polysilsesquioxanes. The organosilicon phosphonates [(EtO)₃Si(CH₂)₃PO(OEt)₂] 1 and [(EtO)₃Si(CH₂)₂PO(OEt)₂] 2 have been used to introduce phosphonate and phosphonic acid functionalities to silica and a polysilsesquioxane. Compounds 1 and 2 have been fully characterised (¹H, ²⁹Si, ³¹P and ¹³C NMR and elemental analysis). Xerogels [from tetraethylorthosilicate (TEOS) or 1,4-bis(triethoxysilyl)benzene (BTESB), and 1 or 2] bearing functionality of the type [O_n/2(EtO)_3 − nSi(CH₂)_mPO(OEt)₂] and, after treatment with concentrated HCl, functionality of the type [O_n/2(EtO)_3 − nSi(CH₂)_mPO(OH)₂], (n can be 0–2, m = 2 or 3) were synthesised and characterised using solid state ²⁹Si, ³¹P and ¹³C NMR spectroscopy, elemental analyses and porosimetry measurements. High surface area mesoporous phosphonic acid-modified silicas with a narrow pore size distribution are described.