Synergy principle of single active centers and microenvironment for Cr-MFI-catalyzed alkane dehydrogenation

Propane dehydrogenation (PDH) to propylene holds immense industrial application value and encompasses pivotal scientific issues in fossil resources utilization, particularly the C-H bond activation and transformation in alkane conversion. Metal-containing zeolites have emerged as efficient catalysts for alkane dehydrogenation. However, the fundamental understanding of how the metal center and zeolite microenvironment participate in alkane dehydrogenation remains elusive. Here we constructed a Cr-MFI zeolite featuring single Cr centers embedded within the MFI framework and utilized this highly efficient PDH catalyst to comprehensively illustrate the synergistic interplay between metal active centers and the zeolite microenvironment for alkane dehydrogenation. Through <i>in situ</i> X-ray absorption spectroscopy (XAS) and <i>in situ</i> Fourier transform infrared (FTIR) spectroscopy, we successfully captured the dynamic evolution of Cr electronic states and the migration of H species to Cr and its adjacent O atoms under PDH conditions. Theoretical calculations and isotope labeling elucidated the synergy principle between Cr active centers and the zeolite microenvironment in Cr-MFI, demonstrating that the zeolite microenvironment intensifies propane activation and the flexible Cr-O-Si centers consecutively extract H* from propane. These findings provide great insights into the dynamic catalytic behavior of metal-zeolite systems under alkane dehydrogenation conditions and offer valuable guidelines for the rational design and optimization of such catalysts for industrial application.