Turning On Catalysis: Incorporation of a Hydrogen-Bond-Donating Squaramide Moiety into a Zr Metal–Organic Framework

Herein, we demonstrate that the incorporation
of an acidic hydrogen-bond-donating
squaramide moiety into a porous UiO-67 metal–organic framework
(MOF) derivative leads to dramatic acceleration of the biorelevant
Friedel–Crafts reaction between indole and β-nitrostyrene.
In comparison, it is shown that free squaramide derivatives, not incorporated
into MOF architectures, have no catalytic activity. Additionally,
using the UiO-67 template, we were able to perform a direct comparison
of catalytic activity with that of the less acidic urea-based analogue.
This is the first demonstration of the functionalization of a heterogeneous
framework with an acidic squaramide derivative.