Preparation of Bifunctional Mesoporous Silica Nanoparticles by Orthogonal Click Reactions and Their Application in Cooperative Catalysis

• Published in: Chemistry : a European journal 2012-12, Vol.18 (52), p.16689-16697
• Main Authors: Dickschat, Arne T., Behrends, Frederik, Bühner, Martin, Ren, Jinjun, Weiß, Mark, Eckert, Hellmut, Studer, Armido
• Format: Article
• Language: English
• Subjects: acid-base catalysis; Chemistry; click chemistry; cooperative catalysis; MCM-41; mesoporous silica; Porous materials; Silica
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201200499

The synthesis of bifunctional mesoporous silica nanoparticles is described. Two chemically orthogonal functionalities are incorporated into mesoporous silica by co‐condensation of tetraethoxysilane with two orthogonally functionalized triethoxyalkylsilanes. Post‐functionalization is achieved by orthogonal surface chemistry. A thiol–ene reaction, Cu‐catalyzed 1,3‐dipolar alkyne/azide cycloaddition, and a radical nitroxide exchange reaction are used as orthogonal processes to install two functionalities at the surface that differ in reactivity. Preparation of mesoporous silica nanoparticles bearing acidic and basic sites by this approach is discussed. Particles are analyzed by solid state NMR spectroscopy, elemental analysis, infrared‐spectroscopy, and scanning electron microscopy. As a first application, these particles are successfully used as cooperative catalysts in the Henry reaction. Cooperative clicking: Bifunctional mesoporous silica particles were synthesized by orthogonal surface chemistry. A thiol–ene reaction, a copper‐catalyzed 1,3‐dipolar cycloaddition and a radical nitroxide exchange reaction were used as orthogonal processes for the introduction of the acid and base functionalities (see scheme). Catalytic activities of these bifunctionalized inorganic/organic hybrid materials were studied on the Henry reaction.