Imine
and its derivatives, serving as vital intermediates to construct
N-containing heterocyclic compounds, are the highly desired products
for fine chemical industry and pharmaceutical industry. With visible
light as environmental-benign energy sources, imines are generally
synthesized with coupling of amines and alcohols or oxidative self-coupling
of amines. However, the coupling of amines and alcohols strategy is
usually catalyzed by noble metal catalyst, and the yield of imines
is still far from satisfactory owing to the formation of overhydrogenation
byproducts. Meanwhile, oxidation self-coupling of amines cannot meet
the requirement for the synthesis of asymmetrical substituted imines.
In this work, CdS quantum dots decorated MIL-101 catalysts have been
constructed as versatile catalysts for photocatalytic synthesis of
imines with two different strategies at low temperature (ice bath).
Strong interactions between CdS quantum dots and MIL-101 carrier are
observed by Raman and UV–Vis DRS measurement results. By taking
the combined advantages of CdS quantum dots and MIL-101 materials,
CdS@MIL-101 multifunctional catalyst is not only feasible to the photocatalytic
coupling of amines and alcohols to synthesize imines under N2 or air atmosphere but also highly active for the oxidative self-coupling
of benzylamine derivatives for the synthesis of imines with air as
photo-oxidant. Noteworthy, the two photocatalytic synthesis strategies
provide an ultra-high selectivity for imine products.
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