Considering the closed packing of supramolecular mediated cage-type (spherical) mesopores inside spherical particles that are typically obtained by the aerosol-assisted process, uniform mesopores cannot be packed so periodically and then the mesopores are less connected and/or occasionally isolated, leading to the formation of low-surface-area mesoporous particles. In this study, we proposed the controlled swelling of such cage-type mesopores for improving their connectivity. Controlled swelling Actually, we succeeded in preparing high-surface-area mesoporous alumina powders using poly(oxyethylene)-block-poly-(oxypropylene)-block-poly(oxyethylene) (EOnPOmEOn) type triblock copolymers such as Pluronic P123. The surface area of the mesoporous alumina powders was originally low (278 m(2) g(-1) without organic additives), which can be drastically increased up to ca. 540 m(2) g(-1) through the controlled welling with suitable addition of 1,3,5-trimethylbenzene and 1,3,5-triisopropylbenzene. The insight is promising for further development of the aerosol-assisted approach for recovering high-quality mesoporous powders and helpful for rational catalyst design by utilizing mesoporous alumina powders with extremely high surface area.