Atomically dispersed ruthenium hydride on beta zeolite as catalysts for the isomerization of muconates

Searching for sustainable polymers requires access to biomass-based monomers. In that sense, glucose-derived cis,cis-muconic acid stands as a high-potential intermediate. However, to unlock its potential, an isomerization to the value-added trans,trans-isomer, trans,trans-muconic acid, is required. Here we develop atomically dispersed low-loaded Ru on beta zeolite catalysts that produce trans,trans-muconate in ethanol with total conversion (to equilibrium) and a selectivity of >95%. We reach very high turnovers per Ru and productivity rates of 427 mM h−1 (~85 g l−1 h−1), surpassing the bio-based cis,cis-muconic acid production rates by an order of magnitude. By coupling isomerization to Diels–Alder cycloaddition, terephthalate intermediates are produced in around 90% yields, circumventing the isomer equilibrium. Isomerization is promoted by Ru hydride species where the hydrides are generated from the alcohol solvent, as evidenced by Fourier transform infrared spectroscopy. Beyond isomerization, the Ru–zeolite and its hydride-forming capacity could be of use as a heterogeneous catalyst for other hydride chemistries, demonstrated by a successful hydride transfer hydrogenation. Muconic acid is an important bio-based chemical; however its applications are limited by the lack of efficient methods to access its trans,trans-isomer. Here the authors address this problem with a catalyst based on single Ru atoms dispersed on zeolite BEA that is capable of unlocking hydride chemistries.