Phosphorylated chitin and cellulose nanocrystals as colloidal bio-templates towards mesoporous aluminophosphates†

This work demonstrates the interest of phosphorylated chitin and cellulose nanocrystals as colloidal bio-templates towards the formation of mesoporous aluminophosphates. Chitin and cellulose nanocrystals (ChitNC and CellNC, respectively) were phosphorylated using POCl₃. This procedure does not affect the internal structure of the nanoparticles while it opens new opportunities for materials’ design. From the analysis of dimensions and zeta potentials of the phosphorylated nanoparticles (ChitNC-P and CellNC-P), we demonstrate notably the enhanced stability of chitin suspensions across a pH range of 4 to 13. Further we investigated the interactions between the polysaccharide nanocrystals and aluminium oxo–hydroxo clusters ε-Al₁₃O₄(OH)₂₄(H₂O)₁₂⁷⁺ to form mesoporous alumina and aluminophosphate materials through spray-drying and calcination in air. The spatial proximity between phosphorous and aluminum sites in the final materials was probed by solid-state NMR studies using notably ²⁷Al{³¹P} REDOR experiments.