DYNAMICAL STUDIES OF ZEOLITIC PROTONS AND ADSORBATES BY PICOSECOND INFRARED-SPECTROSCOPY

The application of (picosecond) nonlinear infrared spectroscopy to inv estigate zeolite catalysts and adsorbates is reviewed. In these time-r esolved experiments, one specific vibration in the zeolite system (i.e ., a zeolite or adsorbate vibration) is selectively excited with an ul trashort (tunable) mid-infrared pulse. The effect of this excitation a nd the subsequent energy relaxation can be monitored real time, provid ing information on the structure of the bare zeolite and adsorption co mplexes. More importantly, with this technique the picosecond energy f low at the catalytic site and the dynamics of the catalyst-adsorbate i nteraction can be investigated: Short-lived transient species (e.g., r eaction intermediates) are observed and the picosecond relaxation rate s and pathways at the catalytic site render insights into the dynamics of the interaction between the zeolite catalyst and its adsorbates at a molecular level. This illustrates the potential of time-resolved in frared spectroscopy in the investigations of catalytic systems.