Development of Single-Site Heterogeneous Catalysts Using Tunable Hydrotalcites as Supports Open Access
Downloadable ContentDownload PDF
Homogenous catalysts consisting of noble metals are expensive, typically non-recyclable, and generate toxic metal waste. Developing long-lived heterogeneous catalyst as alternatives is a main priority for many segments of the chemical industry. We report protocols for the use of layered double hydroxides, such as hydrotalcite clays, as supports for single-site heterogeneous catalysts (SSHCs) based on linkers that afford long-lived, highly active catalysts that are often more active than the homogeneous counterparts. A one-step synthetic method for the SSHC synthesis in flow has been developed, and we show proof-of-concept that SSHCs can be electronically tuned using hydrotalcite support with variable composition. We discuss the development of structure-activity relationships associated with the electronic and geometric interactions of the catalysts and LDHs, and methods for probing how electronic properties of the supported catalysts and supports influence activity, selectivity and stability. Several case studies of Pd and Ir SSHCs will illustrate the challenges and opportunities in rationally optimizing support interactions in order to engineer new catalytic activity for reactions such as C-C couplings, acceptorless dehydrogenation of alcohols and CO2 reduction to formic acid using hydrogen equivalents borrowed from glycerol. The aforementioned reactions are all highly relevant to the replacement of fossil fuel sources of commercial chemicals with renewable bio-based sources.