Salt-templated Synthesis and Morphological Control of Monodisperse Hollow Mesoporous Structures

Hollow mesoporous structures have great potential in catalysis, energy storage and conversion, biomedicine, etc., due to their abundant inner void space and porous permeable shells. However, there is still a lack of efficient, simple and green synthesis methods. Herein, sodium citrate nanoparticles with excellent colloidal stability were used as templates for the direct growth of mesoporous silica shells through the interfacial co-assembly of cetyltrimethylammonium bromide (CTAB) micelles and hydrolyzed oligomer of tetraethyl orthosilicate (TEOS). The hollow mesoporous structures were obtained simply after removal of the CTAB micelles and colloidal sodium citrate nanoparticles by ethanol and water washing. Further studies have shown that electrostatic interactions between negatively charged colloidal sodium citrate nanoparticles and CTAB micelles were key for the polymerization assembly of silicon oxide oligomer on the nanoparticle surface. More importantly, the morphology and shell thickness of hollow mesoporous structures could be accurately adjusted through the control of reaction time. Moreover, the hollow meso. porous structures could improve the mass transfer significantly, which can act as an ideal support for metal catalysts. As a proof of concept, the Au nanoparticles loaded hollow mesoporous silica nanospheres showed excellent catalytic activity for reduction of 4-nitrophenol. This work provided a new insight into the green and simple synthesis of hollow mesoporous materials.