Mesostructures, hierarchically ordered

Figure 11.S TEM images of an ultrathin section of the hierarchically ordered silica mesostructure ZSU-4 obtained with a mixture of silicone surfactant and PEO-PPO-PEO block copolymer as the template (left) X-ray...

Huang Y, Cai H, Feng D, Gu D, Deng Y, Tu B, Wang H, Webley PA, Zhao D (2008) One-step hydrothermal synthesis of ordered mesostructured carbonaceous monoliths with hierarchical porosities. Chem Commun 23 2641-2643... 

Wang X, Bozlrilov KN, Feng P (2006) Facile preparation of hierarchically porous ctubon monoliths with well-ordered mesostructures. Chem Mater 18 6373-6381... 

The present paper provides an overview of the physical properties of silica mesostructures with representative wormhole and lamellar framework structures assembled through S°P pathways. The wormhole framework silica, denoted HMS silica, was assembled using an alkylamine surfactant as the structure director and a silicon alkoxide as the inorganic precursor. The lamellar framework silica with a vesicular hierarchical structure, denoted MSU-G silica, was obtained from tetraethylorthosilicate (TEOS) as the silica precursor and a bi-functional gemini amine surfactant of the type RNH(CH2)2NH2. We then provide examples of the catalytic activity of these disordered mesostructures in comparison to more ordered framework mesostructures such as hexagonal MCM-41. 

The resulting mesoporous layers don t usually exhibit extraporosity at a larger scale, but as smaller pores in the oxide walls (Figure 25.24). ° Due to limitations associated with intrinsic mesostructure characteristics, anisotropy resulting from preferential orientations, or boundaries between ordered domains, the tem-plated mesoporosity is usually not directly interconnected. " In such situations, it does directly define the selectivity of the membrane, which depends on the pore size of the oxide walls. However, the resulting hierarchical porosity (templated mesopores and smaller pores of the oxide walls) favors a decrease in layer permeability. The templated mesoporosity can also be used to functionalize the membrane. 

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