In this study, a novel fibrous nanosilica (KCC-1) based nanocatalyst (Au, Pd, and Cu) with a high surface area and easy accessibility of active sites was successfully developed by a facile approach. KCC-1 with a high surface area was functionalized with multi-carboxylic hyperbranched polyglycerol groups (HPG) acting as robust anchors so that the metal nanoparticles (Au, Pd, and Cu) were well-dispersed on the fibers of the KCC-1 microspheres without aggregation. Because of the amplification effect of HPG, high loading capacities of the nanocatalysts were achieved. The synthesized KCC-1/HPG/X nanocatalyst exhibited excellent catalytic activity for the synthesis of quinazoline-2,4(1H,3H)-diones from CO₂ and 2-aminobenzonitrile under mild conditions due to the easy accessibility of the active sites. High catalytic activity and ease of recovery from the reaction mixture by using filtration after several reuses without any significant loss of performance are additional eco-friendly attributes of this catalytic system.