Synergistic
effects have been discussed extensively in bimetallic
heterogeneous catalysis, but it remains unclear how the effects function
at the atomic scale. Here, we report a dual single-atom catalyst (DSAC)
Ir1Mo1/TiO2 displaying much greater
catalytic chemoselectivity (>96%, at 100% conversion) than comparable
single-atom catalysts (SACs) Ir1/TiO2 (38%,
at 87% conversion) and Mo1/TiO2 (no activity)
for the hydrogenation of 4-nitrostyrene (4-NS) to 4-vinylaniline (4-VA).
Activation of the TiO2-supported bimetallic carbonyl cluster
Ir2Mo2(CO)10(η5-C5H5)2 in an Ar atmosphere affords the
DSAC Ir1Mo1/TiO2. Characterization
of the dual single-atom structure confirms that it consists of well-dispersed
Ir single atoms (Ir1) and Mo single atoms (Mo1) on TiO2. Density functional theory studies reveal that
Ir1 sites effect H2 activation while Mo1 sites are responsible for 4-NS adsorption, with synergistic
cooperation between the two sets of single atoms contributing to the
better catalytic performance for the hydrogenation of 4-NS. This work
provides a deep understanding of synergistic effects in dual single-atom
catalysis.
{[Cu(6)(TTTMB)(8)(OH)(4)(H(2)O)(6)]·8(NO(3))·34.5H(2)O}(n) can reversibly transform to {[Cu(6)(TTTMB)(8)I(3)]·9I·26H(2)O}(n) upon a single crystal to single crystal process. The transformation is accompanied by the formation of weak Cu(2+)I(-) interactions and changes in the coordination numbers, as well as modulation in their properties.
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