Understanding the working principle of sustainable catalytic materials for selective hydrogenation of carbonyls bond in α, β-unsaturated aldehydes

Abstract

The superior hydrogenation of carbonyl (C=O) bonds in α, β-unsaturated aldehydes (UAL) has attracted considerable attention from economic and industrial perspectives. Several efforts have been made because hydrogenation of the olefin (CC) bond is kinetically and thermodynamically preferred over CO bond hydrogenation. Hence, to achieve superior hydrogenation of the targeted CO bond, highly active and durable catalysts are required. Herein, functional hydrogenation catalytic materials and their working principles are thoroughly discussed and apprehended. The active role of noble, non-noble mono/bi-metal catalysts and support materials along with the key factors arising from the structure of catalysts that promotes the CO bond selectivity were thoroughly disclosed. Essential techniques and strategies, such as tuning the surface electronic properties and generating electro-nucleophilic sites via synergistic effects, geometric effects, and applying a confinement or steric effect for improved CO bond hydrogenation, are briefly apprehended. The aggregate analysis suggested two crucial approaches for the engineering of a vastly selective and stable hydrogenation catalytic material: (1) tuning the electronic number of an active noble metal and (2) stabilizing the active noble metal by selecting distinctive support materials, especially metal-organic frameworks (MOFs) owing to its special physiochemical features, to construct robust metal-support interactions. In the end, various crucial key factors and additional active sites that are also encountered to attain the desired selectivity of the CO bond are concisely reviewed. Regardless of the numerous successes, significant development is still essential to expand our understanding of the preferential hydrogenation of challenging CO bonds in UAL.