Facile Synthesis of Spatially-Functionalized Core-Shell Nanocatalysts with 3-D Mesopore Structure

Abstract

Hollow mesoporous silica particles (HMSPs) have recently drawn much attention as nanocatalysts, owing to their benefits and potential for greener chemical processes. Here, improved synthesis of HMSPs exhibiting a shell with a 3-D pore structure is proposed to overcome previous synthetic issues, such as reproducibility, particle size distribution, precise tailoring of size/shell thickness, low yield, etc. Additionally, precisely controlled and selective functionalization with amine groups is achieved owing to careful protection and sequential extraction protocols. To overcome time-consuming and complex multistep extraction procedures, different methods were optimized towards the most efficient protocol. The obtained materials are characterized in terms of structure, porosity and functions, and the confined catalytic activity was tested in a Knoevenagel reaction. The nanocatalysts were compared before and after the core template was removed to confirm that the only catalytic species are free amines located on the inner external surface of the shell (i. e., the surface exposed towards the hollow core).