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

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 (C[dbnd]C) bond is kinetically and thermodynamically preferred over C[dbnd]O bond hydrogenation. Hence, to achieve superior hydrogenation of the targeted C[dbnd]O 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 C[dbnd]O 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 C[dbnd]O 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 C[dbnd]O bond are concisely reviewed. Regardless of the numerous successes, significant development is still essential to expand our understanding of the preferential hydrogenation of challenging C[dbnd]O bonds in UAL.