KF@Metal–Organic Framework Composite as Solid Base in Solvent‐Free Knoevenagel Condensation

The encapsulation of guest molecules in metal–organic frameworks (MOFs) is a powerful strategy for designing functional materials. However, most MOFs and their derivatives exhibit acidic properties. To address the lack of heterogeneous MOF‐based basic catalysts, we developed a series of KF@MOF composites with varying levels of KF loading. The composites were synthesized via vacuum‐assisted evaporative impregnation. Stable microporous MOFs with comparable pore apertures: Alfum (aluminum fumarate), MIL‐88A (MIL = Materials Institute Lavoisier), MOF‐801, and CAU‐10‐H (CAU = Christian Albrechts University) were selected as hosts. Although these composites exhibit lower basicity than the benchmark KF/Al 2 O 3 , they effectively retain the KF guest during catalytic reactions and workup. The acid–base properties of the composites were evaluated semi‐quantitatively using Hammett indicators. Their catalytic performance was assessed in the Knoevenagel condensation, where they function synergistically as both a base catalyst and a dehydration agent, shifting the equilibrium toward the condensation products. Among the series, the KF@CAU‐10‐H composite with 20% KF loading was the most effective. We successfully extended this methodology to the condensation of arylaldehydes with CH‐acids containing a nitrile group. This solvent‐free protocol provides access to substituted acrylonitriles in high yields (32%–99%) with short reaction times of 20–80 min.