Mesoporous Materials

Mesoporous silica materials have received a great deal of attention since the discovery in 1992 that inorganic oxide materials could be templated using self-assembled surfactant mesostructures. The pore size and geometry is highly regular and can be tuned by choice of surfactant as well as controlling the chemistry during synthesis. Our work has concentrated upon an understanding of both the structure of these novel materials and also the formation mechanism. The figure below shows a new minimal surface for the structure of the mesoporous materials SBA-1 which was deduced in our laboratory.

Octahedral/Tetrahedral Molecular Sieves

Microporous materials such as zeolites are based around framework ions which are tetrahedral in nature (in zeolites these are Al and Si). We have been interested to expand the framework connectivity into materials with dual octahedral and tetrahedral framework atoms. In particular this allows the inclusion of large quantities of transition metal ions (such as titanium or vanadium etc.) which offers potential fro the materials in opto-electronic and photo-catalytic applications. The example shown below is the titanosilicate ETS-10, the structure of which was solved at the CMM. A possible polymorph (not synthesised to date) would have a spiral channel system.

Crystal Growth in Microporous Materials

We have an active programme to study crystal growth in porous framework materials. We primarily use atomic force microscopy and electron microscopy to monitor the details of crystal surface structure which in turn leads to an understanding of the fundamental crystal growth processes. Our work involves both experimental studies, as shown in the AFM image below of the surface of a zeolite A crystal as well as calculations of crystal growth processes.

Hierarchical Porous Structures

Combining different levels of porosity into an individual material is an important goal in order to optimise diffusion pathways, rather like the ramified pore structure in the lungs. We have used a variety of methods to achive this end including restructuring of diatomaceous earth. Below is shown an example of a material which displays macro-, meso- and microporosity in a hierarchical porous silca. The macropores are templated with Latex spheres, the meso- and microporosity from block-copolymer templates.