Systematic pore lipophilization to enhance the efficiency of an amine-based MOF catalyst in the solvent-free Knoevenagel reaction.

We systematically lipophilized an amine-based metal-organic framework (MOF) catalyst and applied the functionalized MOFs to the Knoevenagel condensation reaction. A well-defined MOF material composed of both amine- and hydroxy-bearing linkers was reacted with a series of aliphatic isocyanates (isopropyl, -butyl, -hexyl, and tetradecyl) and, incongruously, was found to preferentially react at the hydroxy groups. This selective functionalization yielded MOFs in which the catalytically active amines are confined within highly lipophilic pores, reminiscent of many enzyme active sites. We determined that systematically increasing the lipophilicity of the pores results in a commensurate increase of catalyst efficiency.