A nanoporous metal–organic framework as a renewable size-selective hydrogen-bonding catalyst in water

Abstract

A novel squaramide-containing metal–organic framework (MOF) material has been designed and synthesized. A detailed X-ray crystal structure analysis showed that four squaramides of this MOF adopted two orientations in each dependent nanopore, confirming that two carbonyl and two N–H groups pointed simultaneously to the inside of the one-dimensional nanometer channel. The MOF was applied as an efficient bifunctional hydrogen-bonding catalyst for Michael additions of 1,3-dicarbonyl compounds to nitroalkenes in pure water, boosting the catalytic efficiency by up to approximately five times the value afforded by the homogeneous control and exhibiting a highly size-selective catalytic performance and good renewability. The catalytic mechanism was also discussed in detail. The present study provides a highly promising approach to achieving dual-activation catalytic centers in a single system, which function as microscopic chemical reactors that allow the interaction and fast transport of substrate molecules in their cavities.