One-pot synthesis of hierarchically macro/mesoporous Al2O3 monoliths from a facile sol–gel process

Based on the preparation of ordered mesoporous Al₂O₃ powder using P123/isopropoxide aluminum/HNO₃ reaction system, hierarchically macro/mesoporous alumina monoliths were successfully fabricated by introducing PEG8000 as the phase-segregation initiator to generate macropores. The effects of PEG8000 and P123 contents on the monolithic and hierarchical morphology were investigated systematically. With appropriate selection of the starting composition, monolithic skeletons with bimodal macropores interconnected by mesostructured walls can be synthesized in both the dried gels and calcined samples. The well-defined macropores are in close-celled structure dispersed in large-sized mesoporous matrix. The mesopore size can be regulated by adjusting the PEG8000 content while its shape is governed by P123 content. The well-developed alumina monolith, MMA-P20, exhibits high surface area of 287 m²/g and narrowly distributed mesopores with median size of 13 nm after calcinaton.