Evaluating the catalytic performances of supported transition metal catalysts by positron annihilation lifetime spectroscopy

Supported transition metal catalysts have played a critical role in the modern synthetic chemical industry. Herein, MCM-41 was chemically modified with amino groups and then used as the support of six transition metal cations . The chemical structures , microstructures and dispersions of these supported transition metal cations were carefully characterized by XRD , TEM and BET. The chelations of modified MCM-41 support with these transition metal cations were confirmed by FT-IR and XPS . The reduction reaction of 4-nitrophenol into 4-aminophenol was employed to evaluate the catalytic activities and recyclabilities of these supported transition metal catalysts. Meanwhile, their reactivities with o -Ps species were assessed by positron annihilation lifetime spectroscopy (PALS). It was found that the reduced o -Ps annihilation intensities (ΔI 3 ) were well associated with their catalytic activities while the o -Ps annihilation lifetime values (τ 3 ) were related to their catalytic recyclabilities. In all, the catalytic activities and recyclabilities of supported transition metal cations can be conveniently evaluated by their o -Ps annihilation properties. This method holds great potential in the design and preparation of highly active and stable supported transition metal catalysts.