Mesocellular silica foams

Backvall s group has taken advantage of the catalyst immobilization in mesocellular silica foams (MCFs) to coimmobilize palladium nanoparticles and CALB in MCF, so that each cavity of the support will contain both the lipase and the nano-palladiinn, affording a single and recyclable hybrid catalyst of the DKR for primary amines [115]. The immobilization technique and the DKR of 91 were optimized, obtaining the chiral amide target in maximum yields and ee. 

Wu, Sh., Ju, H., and Liu, Y. 2007. Conductive mesocellular silica-carbon nanocomposite foams for immobilization, direct electrochemistry, and biosensing of proteins. Adv. Funct. Mater. 17 585-592. 

Making use of constrained polymerisation of divinylbenzene on surfactant-modified colloid silica, Jang and Lim prepared carbon nanocapsules and mesocellular foams. Later, they reported that mesoporous carbons with highly uniform and tunable mesopores were fabricated by one-step vapour deposition polymerisation using colloidal silica nanoparticles as template and polyacrylonitrile as carbon precursor. Hampsey et al. recently reported the synthesis of spherical mesoporous carbons via an aerosol-based, one-step approach using colloidal silica particles and/or silicate clusters as template. ... 

Lettow, J.S. Han. Y.J. Schmidt-Winkel, P. Yang, P. Zhao, D. Stucky. G.D. Ying, J.Y. Hexagonal to mesocellular foam phase transition in polymer-templated mesoporous silicas. Langmuir 2000. 16. 8291. 

Further examples of supported catalysts used for ATH of imines include those based on recyclable silica [84], functionalized MCM-41 [85], siliceous mesocellular foam [86] and magnetic mesoporous silica. In the latter case, the reusable immobilized catalyst exhibited high activity and enantioselectivities in the ATH of imines in FA/TEA. It was able to be separated mechanically using an external magnet to facilitate ready recycling [87],... 

A Cu-Box complex supported on monolith (51) was developed for the enantio-selective cydopropanation of ethyl diazoacetate. The flow reactions using (51) provided an increase in enantioselectivities of about 20% relative to those for the homogenous batch process (Scheme 7.38) [142]. Pyridine-oxazolidine based monoliths (52) and (53), whose central metals were Ru and Cu, respectively, were also developed [143,144]. Mesoporous silica was utilized as a support for the Cu-Box complex for asymmetric cydopropanation in a flow reador. Aza(bisoxazoline) was easily immobilized on siliceous mesocellular foam MCF) microparticles, which are... 

More recently, Backvall and coworkers have described a very effective catalyst for the racemization of amines highly dispersed Pd nanoparticles supported in the large pores of silica-based mesocellular foam (MCF) [104]. This catalyst proved to be a more robust catalyst in amine racemization than any other catalysts reported before and is completely compatible with CALB activity. 

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