Template-Directed Fabrication of Highly Efficient Metal–Organic Framework Photocatalysts

Photocatalysis
is a powerful and versatile tool widely applied
in the areas of synthesis chemistry. However, most of the photocatalysts
currently used are homogeneous catalysts, which inevitably face issues
such as product–catalyst separation and recyclability. Addressing
this challenge, we utilized a homogeneous Ru photocatalyst as a structure-directing
template to fabricate a series of isostructural photocatalyst-encapsulating
metal–organic frameworks (photocatalyst@MOFs) with high porosity,
robustness, and photocatalyst loading. The regular channels of MOF
can disperse the encapsulated photocatalysts, promote the mass transfer
of substrates and products, and provide an outstanding substrate confinement
effect, thereby dramatically improving the catalytic activity and
excellent recyclability toward valuable organic reactions. For instance,
the MOF photocatalysts can catalyze the asymmetric Mannich reaction
with ketones with high yields and excellent enantioselectivities (up
to 99% ee), better than the reported photocatalyst. Significantly,
this was the first case that heterogeneous MOF-based photocatalyst
can catalyze the asymmetric Mannich reaction without cocatalysts under
room temperature and visible light. This work not only explores an
avenue to prepare heterogeneous photocatalysts but also broadens the
application scope of MOF-based photocatalysts.