Hybrid Catalyst of a Metal–Organic Framework, Metal Nanoparticles, and Oxide That Enables Strong Steric Constraint and Metal–Support Interaction for the Highly Effective and Selective Hydrogenation of Cinnamaldehyde

Advances and Challenges in Development of Transition Metal Catalysts for Heterogeneous Hydrogenation of Organic Compounds

Actual problems of development of catalysts for hydrogenation of heterocyclic compounds by hydrogen are summarized and discussed. The scope of review covers composites of nanoparticles of platinum group metals and 3d metals for heterogeneous catalytic processes. Such problems include increase of catalyst activity, which is important for reduction of precious metals content; development of new catalytic systems which do not contain metals of platinum group or contain cheaper analogues of Pd; control of factors which make influence on the selectivity of the catalysts; achievement of high reproducibility of the catalyst's performance and quality control of the catalysts. Own results of the authors are also summarized and described. The catalysts were prepared by decomposition of Pd0 and Ni0 complexes, pyrolysis of Ni2+ and Co2+ complexes deposited on aerosil and reduction of Ni2+ in pores of porous support in situ. The developed catalysts were used for hydrogenation of multigram batches of heterocyclic compounds.

Enhanced Selective Hydrogenation of Cinnamaldehyde to Cinnamyl Alcohol over Silica-Coated Pt-CoxOy Hybrid Nanoparticles

Selective hydrogenation of cinnamaldehyde (CAL) to cinnamyl alcohol (COL) is difficult due to the intrinsic difficulty with thermodynamically easier hydrogenation of C═C bonds. In this work, Pt-CoxOy hybrid nanoparticles encapsulated in mesoporous silica nanospheres (Pt-CoxOy@mSiO2) were synthesized by a sol-gel method, which showed greatly improved COL selectivity for hydrogenation of CAL. At 80 °C and 1.0 MPa of H2, Pt-CoxOy@mSiO2 achieved a CAL conversion of 98.7% with a COL selectivity of 93.5%. In contrast, Pt@mSiO2 yields 3-phenylpropanol (HCOL) as the major product with HCOL selectivity of 67.2%, while PtCo@mSiO2 yields 3-phenylpropionaldehyde with selectivity of 51.8% under the same conditions. The enhanced catalytic performance of Pt-CoxOy@mSiO2 for hydrogenation of CAL to COL is ascribed to the Pt surface electron deficiency induced by metal-oxide interaction, and the protection of active NPs by silica shells results in good catalytic stability.

The structure and electronic effects of ZIF-8 and ZIF-67 supported Pt catalysts for crotonaldehyde selective hydrogenation

The structure and electronic effects of ZIF-8 and ZIF-67 supported Pt catalysts for crotonaldehyde selective hydrogenation.

Atomically dispersed Pd-Ru dual sites in an amorphous matrix towards efficient phenylacetylene semi-hydrogenation

Optimizing the active sites to balance the conversion and selectivity of the target reaction has long been a challenging quest in developing noble metal-based catalysts. By dispersing Pd and Ru in an amorphous zirconium hydrogen phosphate matrix cross-linked by ionic inorganic oligomers, highly diluted noble metal (<0.2 mol%) can be utilized as dual single-atom sites in oxides for the semi-hydrogenation of phenylacetylene with optimized conversion and selectivity (both >90%) to styrene. In situ DRIFT-IR results suggested the fast generation of surface hydroxyl groups during the catalytic reaction, indicating the high efficiency of the single-atom sites to dissociate bound H2. This work provides an easily scaled-up method for the production of cost-effective single-atom catalysts extendable to various oxide matrices.

Chemoselective hydrogenation of cinnamaldehyde over a tailored oxygen-vacancy-rich Pd@ZrO2 catalyst

Selective hydrogenation of cinnamaldehyde to hydrocinnamaldehyde is captivating due to its industrial relevance.

Stable Iron Hydroxide Nanosheets@Cobalt-Metal-Organic-Framework Heterostructure for Efficient Electrocatalytic Oxygen Evolution

Most studies are devoted to the use of metal-organic frameworks (MOFs) as templates to construct desirable electrocatalysts in situ by high-temperature pyrolysis. The emergence of heterostructures invokes new opportunities to use the full potential of pristine MOFs as efficient catalysts in the oxygen evolution reaction (OER). Here, a MOF surface-reaction strategy is developed to synthesize MOF-based heterostructures without pyrolysis. Uniform Fe(OH)₃ nanosheets are grown controllably on the Co-MOF-74 surface by a fast "phenol-Fe" reaction that takes advantage of the hydroxyl sites in Co-MOF-74. The resulting Fe(OH)₃ @Co-MOF-74 heterostructure delivers an excellent performance in the OER with a low overpotential of 292 mV at 10 mA cm^-2 . Notably, the introduction of Fe can improve the intrinsic activity of the original Co atom significantly. The turnover frequency in Fe(OH)₃ @Co-MOF-74 (1.209 s^-1 ) is more than 25 times higher than that in Co-MOF-74 (0.048 s^-1 ). This work presents a fresh concept for the fundamental design of advanced pure-MOF-based heterostructures and, thereby, provides a new avenue for the fabrication of other energy-conversion and -storage materials.

Pt nanoparticles supported on YCoxFe1−xO3 perovskite oxides: highly efficient catalysts for liquid-phase hydrogenation of cinnamaldehyde

The Pt/YCo_0.3Fe_0.7O₃ catalyst furnished ca. 95% selectivity to cinnamyl alcohol at nearly full conversion for the selective hydrogenation of cinnamaldehyde.