De Novo Tailoring Pore Morphologies and Sizes for Different Substrates in a Urea-Containing MOFs Catalytic Platform

To better understand
the structure–catalytic property relationship,
a platform of urea-containing MOFs with diverse topologies as hydrogen-bonding
(H-bond) catalyst has been well established in the present work. During
the construction of MOFs, we proposed a new strategy called the isoreticular
functionalization approach in which the desired topological net is
first considered as a blueprint, and then two predesigned functionalized
polydentate ligands link to four different metal clusters by de novo
routes to achieve the MOFs with expected pore structure and catalytic
sites. By means of this strategy, we successfully synthesized four
programmed MOFs (named as URMOF-1–4) with diverse
topologies, pore morphologies, and sizes and distribution of active
sites. Subsequently, we systematically investigated the Friedel–Crafts
reactions of 1-methylpyrrole or 1-methylindole with nitroalkene derivatives
with diverse sizes to assess the catalytic properties of the above-mentioned
URMOFs. These four URMOFs can act as reusable H-bond catalysts and
show varied catalytic capacities and size-selectivity properties.
Most significantly, the open morphologies of pores, large channels
in the framework, and effective distribution of active sites on the
wall of the channel are proved to facilitate catalysis. This urea-containing
MOF catalytic platform provides new insight into the catalytic properties
of MOFs with the same kind of active sites but diverse topologies,
pore morphologies, and sizes and distributions of catalytic sites.