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Understanding Ligand‐Directed Heterogeneous Catalysis: When the Dynamically Changing Nature of the Ligand Layer Controls the Hydrogenation Selectivity
Author(s) -
Schröder Carsten,
Schmidt Marvin C.,
Haugg Philipp A.,
Baumann AnnKatrin,
Smyczek Jan,
Schauermann Swetlana
Publication year - 2021
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.202103960
Subject(s) - ligand (biochemistry) , chemoselectivity , chemistry , catalysis , acrolein , aldehyde , selectivity , heterogeneous catalysis , adsorption , combinatorial chemistry , amine gas treating , surface modification , photochemistry , chemical engineering , organic chemistry , biochemistry , receptor , engineering
We present a mechanistic study on the formation and dynamic changes of a ligand‐based heterogeneous Pd catalyst for chemoselective hydrogenation of α,β‐unsaturated aldehyde acrolein. Deposition of allyl cyanide as a precursor of a ligand layer renders Pd highly active and close to 100 % selective toward propenol formation by promoting acrolein adsorption in a desired configuration via the C=O end. Employing a combination of real‐space microscopic and in‐operando spectroscopic surface‐sensitive techniques, we show that an ordered active ligand layer is formed under operational conditions, consisting of stable N‐butylimine species. In a competing process, unstable amine species evolve on the surface, which desorb in the course of the reaction. Obtained atomistic‐level insights into the formation and dynamic evolution of the active ligand layer under operational conditions provide important input required for controlling chemoselectivity by purposeful surface functionalization.