Advances in fluorescence microscopy for probing the links between zeolite heterogeneity and catalysis

The catalytic performance of zeolites depends not only on framework topology, pore architecture, and acid-site properties, but also on acid-site distribution and accessibility, molecular transport, intracrystalline heterogeneity, and the evolution of carbonaceous species. Conventional characterization methods generally focus on local static structures or bulk-averaged properties. They therefore struggle to relate molecular transport and local reactions to catalytic behavior within the same catalyst particle. Fluorescence microscopy addresses this challenge by converting local chemical environments, molecular transport, and catalytic transformations into spatially and temporally resolved optical signals. This review examines three sources of fluorescence signals: zeolite autofluorescence, externally added fluorescent probes, and reaction-induced fluorescence. We discuss how fluorescence intensity, fluorescence lifetime, polarization, single-molecule trajectories, and super-resolution imaging have been used to elucidate acid-site distribution and local catalytic behavior, pore accessibility and molecular transport, the formation of carbonaceous species and catalyst deactivation, and the effects of intergrowths, grain boundaries, and defects. Current limitations and future opportunities for more selective, quantitative, and OPERANDO fluorescence imaging are also discussed.