Metal-organic frameworks as single-site asymmetric catalysts

Abstract

Metal-organic frameworks (MOFs) are a new class of crystalline solids that can be constructed from a wide selection of inorganic connecting points and an infinite array of organic bridging ligands. Herein is presented the synthesis, characterization and catalytic applications of three new families of metal-organic framework catalysts based on the privileged BINOL, salen, and BINAP chiral ligands. Using these families of materials, the structure-function relationships between the framework architecture and their catalytic performance were evaluated. The BINOL system allowed for the examination of the effects of channel dimension on substrate diffusion, which was elucidated indirectly though the analysis of the enantiomeric excess of the product when using the functionalized framework as a heterogeneous catalyst. Through the use of ruthenium salen-based frameworks, the direct effect of channel dimensions on enantioselectivity was evaluated. New methods of controlling the architecture of these salen-based frameworks were demonstrated through the use of guest counter-ion incorporation. The work on BINOL and salen-based systems culminates in the development of a novel BINAP-based framework that offers a new divergent approach towards the development of multiple MOF-based catalytic systems. This new system was shown to be a competent catalyst for a variety of hydrogenations as well as conjugate additions.