Development of Ambient Nanogibbsite Synthesis and Incorporation of the Method To Embed Ultrafine Nano-Al(OH)₃ into Channels and Partial Alumination of MCM-41

An ultrafine aluminum hydroxide nanoparticle suspension was prepared via the controlled titration of [Al­(H₂O)₆]³⁺ with l-arginine to pH 4.6. The prepared material, predominantly 10–30 nm in diameter, was purified by GPC and subsequently identified as the gibbsite (or hydrargillite) polymorph via FTIR, powder XRD, and elemental analysis. The material’s chemical environment and morphology were probed using ²⁷Al/¹H NMR, FTIR, ICP-OES, TEM-EDS, XPS, XRD, and N₂ adsorption experiments. Furthermore, by incorporating the newly developed synthetic route, Al­(OH)₃ was partially loaded inside the mesopores (2.7 nm) of MCM-41. EDS and NMR analysis indicated that both tetrahedral and octahedral Al (O_h/T_d = 1.4) are incorporated at 11% w/w total Al and that the Si/Al ratio is 2.9, indicating that part of the Al is embedded in the Si framework. In addition, differences in elemental composition between surface XPS and bulk EDS analysis provided insight into the distribution of Al within the material. A higher Si/Al ratio was observed on the external surface (3.6) of MCM-41 compared to that of the internal (2.9) cavities. Estimated O/Al ratios suggest predominantly Al­(O)₃ and Al­(O)₄ motifs present near the core and external surface, respectively. This novel methodology produces Al-MCM-41 with relatively high Al content while preserving the ordered SiO₂ framework and can be used in lateral applications where incorporating hydrated or anhydrous Al₂O₃ is desired