Time-Domain NMR: Generating Unique Insights into the Characterization of Heterogeneous Catalysis in Liquid Phase

Time-domain (TD) nuclear magnetic resonance (NMR) comprises a family of tools for characterizing wetted porosity and surface area, fluid-catalyst surface adsorption energy, liquid distribution in packed beds, and transport of fluids in catalyst materials. These methods are differentiated from NMR spectroscopy in that the data are not analyzed in the frequency domain and often benefit from the use of low magnetic field strength. The increased accessibility of commercial, low-field, benchtop NMR instruments has supported substantial growth in TD NMR research in catalysis. This perspective offers a tutorial on physical phenomena critical to TD NMR methods, a summary of applications in both ex situ and in situ settings, and commentaries on ensuring experimental rigor and opportunities for growth in the field. The unique insights accessible from TD NMR often cover length scales in the tens of nanometers to tens of micrometers and are complementary to other catalyst characterization methods probing molecular structure and identity.