Host matrices frameworks

We also include in this class of quasi-2D nanostructured materials Titania deposited inside ordered mesoporous silica (because an inner coating of mesoporous silica may be realized), or nano-dot type Titania particles well dispersed in the ordered porous matrix. We do not consider here solids which contain linear or zig-zag type TiOTiO-nanowires in a microcrystalline porous framework, such as ETS-4 and ETS-10, notwithstanding the interest of these materials also as photocatalysts,146-151 because these nanowires are located inside the host matrix, and not fully accessible from the gas reactants (the reactivity is essentially at pore mouth). 

Catalytic activity of metal ions coordinated to the framework of mesoporous molecular sieves atracted attention at first. Recently, catalytic activity of the metal ions incorporated into extraffamework positions of the MCM-41 in various reactions was also reported [3], But, the site geometry, coordination and distribution of the metal ions in the extraframework sites of the MCM-41 host matrix are not understood, and only a few papers have dealt with this problem. For dehydrated Mn-(A1)MCM-41, only one type of single cation was reported [4],... 

Recrystallisation from water containing picric acid (PA) gives stable isomorphous yellowish needles, whose structure has been reported The TMA H O framework of these crystals is well defined but the striking diffuse scattering indicates that the PA molecules located in the channels are partially disordered. This inability to position the guest with respect to the host matrix is a feature common to many channel inclusion complexes and makes it difficult to draw conclusions about the details of the host-guest interaction. 

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