Catalytic structures based on cross-linked dendrimers and porous polymers

This project involves the design of new hierarchically structured catalytic systems that possess the vital features recently elucidated for dendrimer-encapsulated nanoparticles (DENs), and subsequently utilise them to develop strategies to achieve the precision construction of catalytic layers in continuous-flow catalytic reactors.

Dendrimer templating has proven to be a versatile method for synthesising metal nanoparticles with very narrow size distributions (1–2 nm range), contributing to the development of homogeneous catalysis in organic synthesis.1,2 However, DENs (e.g. DENs based on PAMAM dendrimers) are also highly sensitive to the local environment (e.g. different solvents) which may lead to the collapse of dendrimers3 and hence the loss of catalytic activity of DENs. Therefore, to integrate DENs within a suitable support can be the best solution to preserve the core-periphery structures of dendrimers and maintain the exceptional characteristics of DENs. Furthermore, from a practical point of view, immobilisation of DENs is also preferred over using them in homogeneous form. Recent development4 has showed the possibility of anchoring DENs (amino-terminated dendrimers) within glass microreactors via thiourea bonding with the (3-aminopropyl)triethoxysilane and p-phenylene diisothiocyanate as linkers. However, the leaching of metal species from DENs under continuous-flow conditions is still a problem. Plus, as mentioned earlier, such catalytic systems with directly immobilised DENs are fastidious in the reaction media (i.e. water and ethanol are preferred) and only applicable to specific cases.
Considering the polymer nature of dendrimers, to cross-link DENs within a porous host polymer matrix may be the best solution to immobilise DENs and at the same time to conserve the template dendrimer’s structure (hence the catalytic activity). If the host polymer matrix can be grown on a macroscopic support (e.g. ceramic open-cell foams, monoliths and/or microchannel reactors), catalytic systems with high stability and catalytic activity can be expected for continuous-flow operation.

The aim of this project is to stabilize metal nanoparticles, with well-defined sizes, compositions, and structures, on macroscopic catalytic supports using cross-linked dendrimer and micro/mesoporous polymer composites overcoming the (i) nanoparticles aggregation challenges and (ii) metal leaching faced by conventional stabilisation approaches. The potential of this new type of catalytic structure will be explored in areas of environment (catalytic hydrodechlorination) and energy (catalytic upgrading of furanic compounds to bio-fuels) applications.

If you wish to apply for this project, please choose ’PhD Chemical Engineering and Analytical Science’ from the list of available programmes.