Nanosized Al-containing mesostructures with a narrow grain size distribution and high aluminum content (Si/Al >= 5) have been facilely prepared via a novel two-step synthetic process, in which the pre-hydrolysis and afterward fast-assembly of inorganic species can be conveniently promoted by acidic aluminum salt and basic catalyst, respectively. Meanwhile, nonionic polyethylene glycol (PEG-4000) added in the synthesis can effectively regulate the grain size and distribution through hydrogen-bonding blocking. Along with high density of acidic sites, the interesting morphology consisted of slight aggregation of nanoparticles with AIMCM-41 structure and thereby formation of a second broader porous system in these interparticle voids may be responsible for its superior activity in the bulky hydrocarbon cracking reactions; i.e. not only good catalytic behavior to the transformation of 1,3,5-triisopropylbenzene even at the lowest temperature tested but also stable cumene conversion can be achieved over the nanoscale mesoporous aluminosilicates. These results reveal that our nanosized mesoporous aluminosilicates are a capable catalyst of high connectivity and accessibility particularly for large molecules. (c) 2007 Elsevier B.V. All rights reserved.