Elucidating the Nanoparticle–Metal Organic Framework Interface of Pt@ZIF-8 Catalysts

Composites of metal nanoparticles encapsulated in metal–organic frameworks (NP@MOFs) have emerged as heterogeneous catalysts for regioselective reactions. While numerous NP@MOF composite combinations have been synthesized, characterization of the nanoparticle–MOF interface and the encapsulated nanoparticle surface have yet to be determined. In this work, Pt@ZIF-8 synthesized by the controlled encapsulation method was chosen as a representative NP@MOF, and in situ characterization methods coupled with density functional theory (DFT) calculations were used to probe the nanoparticle surface. CO adsorption diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) revealed that Pt@ZIF-8 exhibits red-shifted linear- and bridge-bound CO peaks and a linear peak associated with cationic Pt. DFT calculations and 1H NMR suggest that these sites arise from the binding and electronic donation of the MOF linker, 2-methylimidazole, to the Pt surface. DRIFTS under argon reveals that linker fragments may be pre...