Porous silica and polysilsesquioxane with covalently linked phosphonates and phosphonic acids

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