Oligomeric Surfactant and Triblock Copolymer Syntheses of Aluminum Organophosphonates with Ordered Mesoporous Structures

Abstract

Mesostructural control of aluminum organophosphonates (AOPs) with methylene groups inside the inorganic−organic hybrid frameworks was performed by using oligomeric surfactants (C16EO10 and C16EO20) and triblock copolymers (EO80PO30EO80, EO106PO70EO106, and EO20PO70EO20). The templating by oligomeric surfactants with hexadecyl chains that directed the formation of 2-D hexagonal mesostructured and mesoporous AOPs (BET surface areas; ∼579 m2 g-1, pore volumes; ∼0.53 cm3 g-1), especially highly ordered materials, can be obtained by using C16EO20. Mesoporous materials with 2-D hexagonal phases (∼279 m2 g-1, ∼0.76 cm3 g-1) were also prepared through triblock copolymer templating. The pore diameters (6.0−9.2 nm) were largely expanded by using triblock copolymers as compared with those of oligomeric surfactant templated materials (3.3−3.8 nm). Low-temperature calcination of the mesostructured AOPs was useful for removing surfactant molecules to afford periodic non-silica-based hybrid mesoporous materials. Once internal organic moieties are eliminated by calcination at high temperatures, the frameworks are composed of only inorganic units containing two adjacent phosphate groups (−P−OH + HO−P−). Further condensation in the inorganic frameworks is therefore not preferable. Inorganic units are supposed to be restructured to form aluminophosphate-like frameworks (−Al−O−P−) composed of alternating AlO4 and PO4 units and then the mesostructures collapse. Therefore, mesostructural stabilities of AOPs are related to stabilities of methylenediphosphonate groups (⋮PCH2P⋮) and the inner organic groups of the hybrid frameworks.