Jian-Lei Qi,Dan Zhou,Qin-Qin Xu,Jian-Zhong Yin,Kun-Peng Yu,Hai-Xin Sun
In recent years, single-atom catalysts (SAC) have emerged as a new frontier in the field of heterogeneous catalysis owing to their unique properties and minimized metal dosage. Herein, the Pd-ZIF-8 single-atom catalyst was successfully fabricated using ZIF-8 as support, and Pd(hfac) 2 as the precursor using the supercritical CO 2 deposition method. Aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (AC-HAADF-STEM) images confirmed the formation of uniformly dispersed Pd atoms. Supercritical CO 2 has the advantage of zero-surface tension and high diffusibility, it can carry the molecules of Pd precursor into the micropores of ZIF-8. The dissolution and diffusion of precursor were observed by a visual view cell and the mechanism of the preparation was analyzed. Finally, semi-hydrogenation of phenylacetylene to styrene was performed to evaluate the catalytic activity of the prepared Pd-ZIF-8 catalyst. The conversion rate of 80.7% and selectivity of 92.2% were obtained at 70 °C and 4 h in the semi-hydrogenation of phenylacetylene.
Cu single atoms dispersed on N-doped carbon materials (Cu-NC) were obtained after supercritical CO 2 deposition and decompression, without further post-treatment. AC-HAADF-STEM, STEM , XRD , ICP-OES, and XPS results confirmed that the Cu atoms were equably dispersed over the N-doped carbon (NC) support with the loading of 0.80 wt%. The catalytic performance of Cu-NC in solvent-free oxidation of phenylcarbinol to benzaldehyde was investigated, and the conversion of 73.9% and selectivity of 85.7% were obtained at 50 °C for 1 h. A high-pressure view cell was used to observe the dissolution and diffusion for Cu(acac) 2 in scCO 2 . The stability of Cu-NC structures and the formation path of active oxygen species (O*) on different configurations were predicted by density functional theory (DFT) calculations, and CuN 3 C 1 was found to be more conducive to the activation of tert-butyl hydroperoxide (TBHP).
危险品化学品经营许可证（带存储）