Organically modified porous hydroxyapatites: A comparison between alkylphosphonate grafting and citrate chelation

Two alternative methods to prepare organically modified porous hydroxyapatites following a “one pot” approach were compared. The partial substitution of inorganic phosphates by alkylphosphonates leads to mesoporous materials with high specific surface area (>200 m2 g−1). The incorporation of the organic moieties within the hydroxyapatite structure is confirmed by Infra-red and solid-state NMR spectroscopy and depends on the nature of the alkyl chain. However, it induces a significant loss of the material crystallinity. In contrast, the introduction of citrate, a calcium-chelating agent, to the precursor solution does not improve the material specific surface area but allows a better control of the hydroxyapatite structure, both in terms of crystallinity and pore size distribution.