Understanding the Dynamics of Fluorescence Emission during Zeolite Detemplation Using Time Resolved Photoluminescence Spectroscopy

Time resolved photoluminescence spectroscopy (TRPS) shows potential as a sensitive, nondestructive, high throughput, label-free laser-based spectroscopy technique capable of analyzing low concentrations of organic species adsorbed on and within zeolite pores. Here we report the results from a study that uses TRPS to characterize photoluminescence (PL) arising from synthesized chabazite framework zeolites at three different stages of the detemplation process (from uncalcined, partially calcined, and calcined zeolites). Temporal resolution was used to demonstrate the steric confinement effects of organic structure directing agents (OSDAs) within a zeolite framework and therefore to establish a signature region for determining the presence of the template. Gated spectra comparisons between an uncalcined zeolite and a partially calcined zeolite demonstrated the presence of template alongside the proliferation of template-derived combustion products. An analysis of lifetime values demonstrated the ability for TRPS to track depletion of OSDA and establish a characteristic PL spectrum for a clean zeolite. The sensitivity of the technique is high enough to reveal that there is still residual organic material remaining in a zeolite even after an extended thermal detemplation process.