Using　poly(acrylic　acid)　(abbreviated　as　PAA)　as　a　shell,　bimodal　mesoporous　silicas　(abbreviated　as　BMMs)　as　a　core,　and　bipyridine-proline　(abbreviated　as　Z)　as　an　active　species,　a　facile　approach　for　preparation　of　the　P-Z@BMMs　nanocomposites　with　core–shell　structure　was　proposed,　which　was　used　as　a　suitable　pH-sensitive　catalyst　for　asymmetric　aldol　reaction　between　p-nitrobenzaldehyde　and　cyclohexanone.　Their　microstructural　features　and　physicochemical　properties　were　extensively　characterized　by　various　methods,　such　as　powder　X-ray　diffraction　patterns,　N2　adsorption–desorption　isotherms,　the　scanning　(and　transmission)　electron　microscopy　images,　the　dynamic　light　scattering　measurements,　the　thermogravimetric　analysis,　the　elemental　analysis,　and　the　Fourier　transform　infrared　spectroscopy　spectra.　Particularly,　their　fractal　evolution,　the　pair　distance　distribution　function,　and　the　Porod　plots　were　demonstrated　via　the　small-angle　X-ray　scattering　patterns.　The　results　elucidated　that　the　PAA　was　successfully　incorporated　onto　the　external　amino-modified　surfaces　of　the　mesoporous　BMMs,　and　the　particles　having　PAA　grafted　thereon　had　a　pH-responsive　shell　in　thickness　of　around　0.97　nm　for　controlled　release　of　Z　species　by　adjusting　pH　value　of　the　reaction　medium.　Besides,　the　synthesized　P-Z@BMMs　presented　the　satisfactory　catalytic　yields　(around　80%)　in　comparison　with　the　homo-　and　heterogeneous　catalytic　system　using　Z　or　Z@BMMs　as　the　catalysts.　©　2023　The　Author(s)