Supramolecular catalysis in flow: Reversible anchoring of precious catalysts for water-based reactions - theory and experiment.

Homogeneous catalysts are capable to mediate a number of unique transformations, that cannot be achieved by the conventional heterogeneous catalysts. However, the intrinsic drawbacks of separation and recycling difficulties often block their industrial application. In order to develop a catalysis system that combines the advantages of both homogeneous catalysis and heterogeneous catalysis, we propose to develop a novel flow catalytic system, that would benefit from the use of the unique structures of pillararenes as supramolecular hosts. First we are going to design a pillararene-based supramolecular host and a catalyst-linked guest that is strongly bound to host. Then the designed supramolecular host will be immobilized on a surface to capture the guest molecules with a homogeneous catalytic site on the tail. The non-covalent interaction between guest molecules (catalyst) and host molecules (pillararenes) will be used to prevent the catalyst from leaching. Such a semi-homogeneous catalyst is expected to be strongly bound to the macrocycles on the support. Because the non-covalent interaction will be designed is such a way that itis reversible under specific conditions, the deactivated catalyst can be removed and regenerated by specific stimulation treatments such as pH, salt, environment polarity, etc.