Visualizing Composition and Functionality of Porous Catalysts Using Dual-Emissive Fluorescent Nanoprobes

The performance of heterogeneous catalyst bodies is closely related to the accessibility and properties of their catalytically most active regions. Visualizing and understanding the composition and functionality of these multicomponent hierarchically structured materials is often time-consuming and expensive. To overcome these challenges, fluorescent nanoprobes have been employed to visualize heterogeneous, complex material composition. So far, fluorescence microscopy approaches are limited to the measurement of spatial heterogeneities of only one propertysuch as accessibility or acidityin a single measurement. In this work, we introduce a dual-emissive solution containing carbon dots and porphyrin nanoprobes to simultaneously map different material domains and properties within heterogeneous catalyst particles. We investigated catalyst components (oxides and supports), spray-dried cracking catalysts, and extruded catalysts. The selective adsorption as well as the aggregation of the probes affect their fluorescence emission characteristics, allowing us to identify regions with similar properties and composition. Our multiprobe staining method is a facile approach for high-throughput composition and property mapping of porous materials, including solid catalysts and adsorbents.