Carbon-carbon coupling chemistries such as aldolization underlie several strategies for valorizing biomass-derived platform molecules to sustainably produce commodity chemicals, specialty chemicals, and fuels. Understanding the nature of the sites responsible for such reactions and how to tune them is crucial for directing novel catalyst design. Among the most catalytically active and tunable materials for such reactions are high surface area mixed metal oxides derived from the thermal decomposition of layered double hydroxides (LDHs). Their catalytic performances are highly sensitive to the identities and ratios of the metals present (commonly one divalent and one trivalent metal) as well as both the LDH synthesis and thermal decomposition conditions. While these materials have been studied, much of the work on these materials to date lacks clear connections between structural properties, intrinsic catalytic performance, and quantum chemical theories, especially with respect to bimolecular aldolization reactions.<br/><br/>In this work we synthesized Mg-Al mixed oxides via the thermal decomposition of alkali-free layered double hydroxide precursors and examined them in the liquid-phase aldolization of acetone as a model reaction. Avoiding alkali-based syntheses limits the impact played by non-structural impurities in the final oxide framework. Thermal and structural characterizations demonstrate the requirements for LDH decomposition and carbonate removal. Reactivity trends and site requirements in acetone coupling are examined via data-fitted reaction kinetics models and discussed in connection with ex-situ and in-situ site titration experiments as well as infrared spectroscopy. Additional details are gathered by comparison with quantum chemistry simulations of acetone aldolization over model Mg-Al surfaces. These studies lay the intellectual groundwork required to rationally develop new mixed oxide catalysts for the selective aldolization of biomass-derived oxygenates.

Controlling aldolization over Mg-Al mixed oxides derived from alkali-free layered double hydroxides

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