Nonsacrificial Self‐Template Synthesis of Colloidal Magnetic Yolk–Shell Mesoporous Organosilicas for Efficient Oil/Water Interface Catalysis

• Published in: Small (Weinheim an der Bergstrasse, Germany) Germany), 2019-04, Vol.15 (14), p.e1805465-n/a
• Main Authors: Yu, Lei, Pan, Panpan, Zhang, Yu, Zhang, Yi, Wan, Li, Cheng, Xiaowei, Deng, Yonghui
• Format: Article
• Language: English
• Subjects: Catalysis; Crosslinking; Gold; heterojunction structure; Heterojunctions; Interface reactions; Iron oxides; magnetic microspheres; mesoporous organosilica; Microspheres; Morphology; Nanoparticles; Nanotechnology; Open channels; pickering emulsion catalysis; Recyclability; Selectivity; Styrenes; Synthesis; Water pollution; yolk–shell structure
• ISSN: 1613-6810; 1613-6829
• DOI: 10.1002/smll.201805465

Using interfacial reaction systems for biphasic catalytic reactions is attracting more and more attention due to their simple reaction process and low environmental pollution. Yolk–shell structured materials have broad applications in biomedicine, catalysis, and environmental remediation owing to their open channels and large space for guest molecules. Conventional methods to obtain yolk–shell mesoporous materials rely on costly and complex hard‐template strategies. In this study, a mild and convenient nonsacrificial self‐template strategy is developed to construct yolk–shell magnetic periodic mesoporous organosilica (YS‐mPMO) particles by using the unique swelling–deswelling property of low‐crosslinking density resorcinol formaldehyde (RF). The obtained YS‐mPMO microspheres possess an amphiphilic outer shell, high surface area (393 m2 g−1), uniform mesopores (2.58 nm), a tunable middle hollow space (50–156 nm), and high superparamagnetism (34.4–37.1 emu g−1). By tuning the synthesis conditions, heterojunction structured yolk–shell Fe3O4@RF@void@PMO particles with different morphologies can be produced. Owing to the amphipathy of PMO framworks, the YS‐mPMO particles show great emulsion stabilization ability and recyclability under a magnetic field. YS‐mPMO microspheres with immobilized Au nanoparticles (≈3 nm) act as both solid emulsifier for dispersing styrene (St) in water and interface catalysts for selective conversion of St into styrene oxide with a high selectivity of 86%, and yields of over 97%. A nonsacrificial self‐template method is developed to synthesize yolk–shell magnetic mesoporous microspheres with mesoporous organosilica shell containing encapsulated Au nanoparticles. These nanoparticles are used as magnetically recyclable nanocatalysts for oil/water interface catalysis by virtue of the unique amphipathy of the organosilica shell and their radially aligned mesoporous channels.