Cascade reactions with Zeolites in compartmentalized settings

CaZeo uses zeolites to overcome thermodynamic barriers in cascade processes, instrumentalizing the zeolite micropores to compartmentalize the reaction space. As a pilot case, the endergonic hydrogenation of CO2 to CO inside a small-pore zeolite is coupled to an exergonic homogeneously catalyzed carbonylation of an alkene outside the zeolite, yielding in one step an ester product with a CO2-derived functional group. Critically, undesired alkene hydrogenation is impeded by the narrow zeolite channels. CaZeo’s overall chemical targets include: (i) to re-integrate CO2 into oxygenated compounds, like esters, aldehydes, glycolaldehyde, isoprenol etc., in which at least one oxygenated function is sourced from CO2, via a Reverse Water Gas Shift Reaction to CO, or via selective CO2 hydrogenation to HCHO; (ii) to use zeolites as generators of small, reactive (or even toxic) molecules like isocyanates or isocyanides, starting from safe precursors like N,N-dialkylureas or N-alkylformamides; (iii) to upgrade polyamide-6,6 by ammonolysis and an ensuing zeolite-catalyzed reaction that convergently transforms the N-functionalized molecular mixture to valuable 1,6-hexanediamine. In CaZeo’s conceptual framework, reactions are spatially partitioned and orthogonalized to each other, overcoming the incompatibility conundrum of catalytic cascades and the equilibrium limitations of isolated reactions. In a more advanced development, pore systems with different diameters within one zeolite crystal are used as compartments. Advanced X-ray absorption spectroscopy monitors the monometallic or cooperative bimetallic active sites in the zeolites. The spatial organization is visualized with high-resolution electron and fluorescence micro(spectro)scopies, giving shape to the envisioned compartments. CaZeo provides catalytic technology that is safe and sustainable, recycles nitrogen-containing (waste) polymers to high quality building blocks, and re-integrates CO2 in chemicals.