Investigation on Hydrogenation of Metal-Organic Frameworks HKUST-1, MIL-53, and ZIF-8 by Hydrogen Spillover

The stabilities of three moisture-stable MOFs containing different metal clusters, i.e., HKUST-1 (Cu), MIL-53(Al), and ZIF-8 (Zn), were investigated in dihydrogen and dissociated hydrogen (caused by doped Pt nanoparticles) environments. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and X-ray-excited Auger electron spectroscopy (XAES) results showed that all three MOFs were stable in dihydrogen environment. However, the structure of Pt-doped HKUST-1 collapsed in the presence of dissociated hydrogen due to the higher reduction potential of Cu compared with H, and the degree of reduction that occurred to the divalent copper in HKUST-1 increased with temperature. Unlike HKUST-1, MIL-53 and ZIF-8 maintained their structures in both dihydrogen and dissociated hydrogen environments at temperatures up to 150 degrees C. Moreover, comparison of Pt-doped HKUST-1 samples synthesized by chemical vapor deposition (CVD) and incipient wetness impregnation showed that the contact between the doped Pt particles (dissociation source) and MOFs (receptor) significantly affected hydrogen spillover.