Lattice-strained metal oxides often display enhanced
catalytic
activity and selectivity on activation of C–H, CC,
CO, and O–H bonds in bio-oxygenates. However, limited
experimental studies have been conducted on the structure sensitivity
for tandem reactions, particularly on complicated surface redox chemical
chain reactions over strained oxide materials. In this work, we employed
transfer hydrogenation of levulinate as a representative example to
illustrate how lattice strain affects tandem oxidation (dehydrogenation,
C–H/O–H bond cleavage) and reduction (hydrogenation,
CO bond saturation) reactions. The key finding is that lattice
strain at MnO
x
–CuO
x
boundaries within bimetallic MnCu oxides leads to
a highly unsymmetrical strain across the interface and lattice distortion.
Such unique behaviors further induce the Jahn–Teller effect
for electronic reconfiguration and field split for Mn 3d orbitals.
Thus, tandem H2 generation and hydrogenation of levulinate
to valerolactone can occur much more efficiently with a fivefold enhancement
over monometallic oxide catalysts. Detailed characterization of fresh
and sintered catalyst samples further demonstrated the critical role
of expansion of the Mn–O facet and phase segregation in facilitated
chemical chain reactions. The design principles discussed in this
work could be potentially applied for other non-noble oxide catalysts
in energy and environmental fields.
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