Materials synthesis

A number of materials types are of interest for CATMAT; microporous materials (zeolites, coordination polymers = metal-organic framework structures MOFs); mesoporous materials; oxides as supports, membranes and sources for reactive oxygen; layered materials (hydrotalcites) as supports; metal and oxide nanoparticles, etc. An overall vision is to utilize our strength in material synthesis as a basis for approaching rational design of improved catalysts and adsorbents.

Hydro/solvothermal methods are adopted for synthesis of micro-and mesoporous materials. Typically teflon lined autoclaves are used. The products could we well crystalline e.g. fibers or platelets, and could delicately depend on synthesis parameters like temperature, pH, reagent source, additives, templates, heating profile, holding time, etc. (see picture to the right)
The crystallization process can be followed by in-situ X-ray diffraction, as visualized by the 3D-pattern below where the growth of one phase takes place on the expense of another.

MOFs are similarly synthesized solvothermally. The aim is to achieve compounds that keep their microporosity upon removal of solvent, thus enabling (selective) adsorption or catalytic behaviour (from purposely introduced transition metal containing building units).

Oxide supports and materials are typically made by a ceramic route (soft-chemistry being utilized when high quality samples are required at milder conditions). For depositing reactive metal, incipient wetness is used with subsequent calcination and activation steps.

Synthesis of metalorganic/organometallic molecules is of high importance, both for studies of homogeneous catalyst systems, as precursors for MOF synthesis and as precursors for thin film deposition methods that are used for providing controlled, finely dispersed deposition of oxide and metal components on large-area surfaces by means of ALCVD (atomic layer chemical vapour deposition), see figure.

Of interest is further to take advantage of new knowledge related to nanostructured materials. E.g. layered hydrotalcites (exhibiting memory effect subsequent to calcination and repeated exposure to humidity/water) are used as supports. However, these can at the same time act as precursors for metal nanocrystals that are formed upon subjecting the material to reducing atmospheres. A fascinating aspect with such layered materials is their ability to delaminate under certain specific conditions. Thereby small flakes are brought into solution. These can subsequently be reconstructed to various types of materials being of importance for catalysis. Other relevant synthesis activities comprise growth of oxide nanoparticles with controlled sized and morphology.

High throughput methods (combinatorial techniques) have been developed and are used in order to more efficiently scan the complex multiparameter space connected with synthesis, materials and catalyst development and optimation.

Published September 19, 2006