Understanding Heterogeneous Catalytic Hydrogenation by Parahydrogen-Induced Polarization NMR Spectroscopy

Parahydrogen-induced polarization (PHIP) is an NMR hyperpolarization technique with the ability to increase the NMR sensitivity by serval orders. The generation of hyperpolarization in hydrogenation reactions is associated with a pairwise addition behavior, which is sensitive to the properties of catalysts and the reaction process, making it a powerful tool for the characterization of catalyst properties and elucidation of reaction mechanisms. In this Perspective, we provide an in-depth overview of the heterogeneous PHIP (HET-PHIP) technique and its application in heterogeneous catalytic hydrogenation. The fundamentals of HET-PHIP are introduced. We describe how HET-PHIP can be used to obtain information about the morphology and electronic properties of supported monometallic catalysts, bimetallic catalysts, and zeolites as well as the facet effect and strong metal-support interaction (SMSI) effect in hydrogenation. Advances in the mechanistic understanding of catalytic hydrogenations by using HET-PHIP are discussed with representative work. We propose the current limitations and prospects of the HET-PHIP technique in catalytic hydrogenation reactions.