Bifunctional Copper Metal–Organic Framework Catalyst for Late-Stage Functionalization of Alkenes

Multifunctional catalysts in organic synthesis are highly
attractive,
particularly in the construction of complex molecules. In this work,
we report a heterogeneous bifunctional Cu-based metal–organic
framework (MOF) catalyst, IMU-108, serving as both a photoredox catalyst
and a cross-coupling catalyst. IMU-108 was synthesized on a gram scale
from Cu(NO3)2·3H2O and 5-mercaptoisophthalic
acid precursors through a simple refluxing device. The structure of
IMU-108 is formed via an in situ S–S bridge
bond connecting zero-dimensional metal–organic polyhedra (MOPs),
each composed of 12 Cu–Cu paddle-wheel motifs. These interpolyhedral
S–S bonds result in a rigid geometric structure and ensure
inner MOPs remain bench-stable while maintaining catalytic activity.
We demonstrate the capacity of IMU-108 in heterogeneous photoredox-catalyzed
cross-coupling of styrenes and α-bromo esters with boronic acids
to yield various substituted 1,1-diaryl alkanes in a single step.
The versatility of this method enables late-stage functionalization
of complex molecules without the need for de novo synthesis. IMU-108 exhibits good reusability, maintaining its catalytic
activity over ten consecutive reaction cycles. Furthermore, computational
and mechanistic studies suggest that coordinatively unsaturated copper
species on the surface of IMU-108 served as catalytically active sites,
possessing competent Single-Electron Transfer (SET) reduction ability
and facilitating cross-coupling reactions.