Switching the Channel Screening Effect of Metal-Organic Frameworks to Control the Selectivity of Furfural Hydrogenation.

The adsorption configuration regulation of molecules on the metal site is crucial in the targeted conversion of specific functional groups. Herein, we propose a strategy to adjust the adsorption configuration of substrate molecules by switching the channel screening effect of MOF, thereby achieving the targeted regulation of the selective hydrogenation pathway of furfural. Specifically, two Pd-containing MOF with different Pd locations were fabricated, in which Pd nanoclusters are confined within the MOF cavities and Pd nanoparticles grow on the MOF external surface. Since furfural must pass through the MOF to contact with the Pd cluster, thus forcing furfural to present a linear adsorption configuration and selectively activates the C═O bonds. In contrast, surface Pd particles shield the channel effect, allowing furfural to adopt a thermodynamically stable planar adsorption mode, resulting in hydrogenation of both C═O and C═C bonds. This work provides insights into the adjustment of substrate adsorption configurations, and the proposed channel screening adsorption mechanism also provides ideas for designing catalysts with complex molecular orientation conversion.