Insights into the Interfacial Effects in Heterogeneous Metal Nanocatalysts toward Selective Hydrogenation

Abstract

Heterogeneous metal catalysts are distinguished by their structure inhomogeneity and complexity. The chameleonic nature of heterogeneous metal catalysts have prevented us from deeply understanding their catalytic mechanisms at the molecular level and thus developing industrial catalysts with perfect catalytic selectivity toward desired products. This Perspective aims to summarize recent research advances in deciphering complicated interfacial effects in heterogeneous hydrogenation metal nanocatalysts toward the design of practical heterogeneous catalysts with clear catalytic mechanism and thus nearly perfect selectivity. The molecular insights on how the three key components (i.e., catalytic metal, support, and ligand modifier) of a heterogeneous metal nanocatalyst induce effective interfaces determining the hydrogenation activity and selectivity are provided. The interfaces influence not only the H2 activation pathway but also the interaction of substrates to be hydrogenated with catalytic metal surface and thus the hydrogen transfer process. As for alloy nanocatalysts, together with the electronic and geometric ensemble effects, spillover hydrogenation occurring on catalytically “inert” metal by utilizing hydrogen atom spillover from active metal is highlighted. The metal–support interface effects are then discussed with emphasis on the molecular involvement of ligands located at the metal–support interface as well as cationic species from the support in hydrogenation. The mechanisms of how organic modifiers, with the ability to induce both 3D steric and electronic effects, on metal nanocatalysts manipulate the hydrogenation pathways are demonstrated. A brief summary is finally provided together with a perspective on the development of enzyme-like heterogeneous hydrogenation metal catalysts.

Surface Molecule Manipulated Pt/TiO2 Catalysts for Selective Hydrogenation of Cinnamaldehyde

“…Previous attempts to improve the chemoselectivity of metal nanocatalysts mainly focused on controlling the size, shape and composition of metal NPs, and, the interactions between metal and supports (1-6). More recent researches have seen an increased focus on understanding the interactions between adsorbates at nanoscale interfaces of heterogeneous catalysts (7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24). But, how these interactions can be precisely regulated to tune the chemical reactivity remains elusive.…”

Mesoporosity‐Enabled Selectivity of Mesoporous Palladium‐Based Nanocrystals Catalysts in Semihydrogenation of Alkynes

“…Generally, Pd‐based catalysts need to be passivated for energetically avoiding further over‐hydrogenation of alkenes to industrially unfavorable alkanes [2] . Currently, there are three main passivation methods, including fabrication of Pd multicomponent alloys, formation of strong Pd–support interactions, and introduction of organic modifiers on Pd, to passivate Pd catalysts and further tune their hydrogenation selectivity [2a, 3] . However, all the passivation strategies required precise engineering of Pd active sites at atomic/molecular levels, which likely complicated the catalyst synthesis and limited their further applications to some extent.…”

Recent Progress in Pd-Based Nanocatalysts for Selective Hydrogenation

“…In the past decades, many efforts have been made to design highly selective and active Pd-based catalysts for selective hydrogenation. 11 − 17 For instance, Grabovskii et al have described the recent advances in palladium catalysts deposited on various inorganic and organic for C=C bond hydrogenation. 18 Also, Sajiki and co-workers have also outlined the effect of support, such as chelate resin, ceramic, spherically shaped activated carbon, 3 Å molecular sieves, and boron nitride, on the selective hydrogenation performance over heterogeneous palladium catalysts.…”