Molecular approaches to heterogeneous catalysis

Coordination Chemistry Reviews, Journal Year: 2021, Volume and Issue: 448, P. 214179 - 214179

Published: Sept. 1, 2021

In most applications in industry involving catalysis, heterogeneous catalysts are preferred over their homogeneous counterparts when available. However, the former cannot be easily made as selective for complex chemical conversions latter. Selectivity requires control of structural and electronic properties catalytic sites at a molecular level, that is general quite difficult to accomplish solids. Nevertheless, number novel approaches have been advanced recent years toward goal. this brief Perspective we provide personal view some avenues available make highly catalysts. First, discuss possibility tethering or otherwise immobilizing on solid surfaces. Alternatively, complexity can added surfaces via adsorption discrete modifiers. Isolated with unique characteristics also created during after synthesis The structure exposed facets solids themselves exploited performance. Finally, nanostructures such Janus core-shell nanoparticles synthesized employed scaffolds multiple functionalities. A few examples all these methodologies, mainly from our own laboratory, provided, discussion pros cons each approach provided.

Language: Английский

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Synthesis and Surface Attachment of Molecular Re(I) Complexes Supported by Functionalized Bipyridyl Ligands

Inorganic Chemistry, Journal Year: 2023, Volume and Issue: 62(5), P. 2359 - 2375

Published: Jan. 24, 2023

Eleven 2,2'-bipyridine (bpy) ligands functionalized with attachment groups for covalent immobilization on silicon surfaces were prepared. Five of the feature silatrane functional to metal oxide coatings surfaces, while six contain either alkene or alkyne hydrogen-terminated surfaces. The bpy coordinated Re(CO)5Cl form complexes type Re(bpy)(CO)3Cl, which are related known catalysts CO2 reduction. Six new characterized using X-ray crystallography. As proof principle, four molecular Re immobilized a thin layer TiO2 silicon. surface-immobilized photoelectron spectroscopy, IR and cyclic voltammetry (CV) in dark one representative example light. CO stretching frequencies attached similar those pure complexes, but CVs less analogous. For two comparison electrocatalytic reduction performance showed lower Faradaic efficiencies than same complex solution under conditions. In particular, containing linked an amide linker poor catalytic control experiments suggest that linkers conjugation redox-active ligand not stable highly reducing conditions alkyl more stable. A conclusion this work is understanding behavior semiconducting complicated have previously been metallic electrodes.

Language: Английский

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Silica Supported Organometallic Ir^I Complexes Enable Efficient Catalytic Methane Borylation

Journal of the American Chemical Society, Journal Year: 2023, Volume and Issue: 145(14), P. 7992 - 8000

Published: March 30, 2023

Catalytic C-H borylation is an attractive method for the conversion of most abundant hydrocarbon, methane (CH4), to a mild nucleophilic building block. However, existing CH4 catalysts often suffer from low turnover numbers and conversions, which hypothesized result inactive metal hydride agglomerates. Herein we report that heterogenization bisphosphine molecular precatalyst, [(dmpe)Ir(cod)CH3], onto amorphous silica dramatically enhances its performance, yielding catalyst 12-times more efficient than current standard borylation. The affords over 2000 turnovers at 150 °C in 16 h with selectivity 91.5% mono- vs diborylation. Higher loadings improve yield monoborylated product (H3CBpin) 82.8% >99% being achieved 1255 turnovers. X-ray absorption dynamic nuclear polarization-enhanced solid-state NMR spectroscopic studies identify supported precatalyst as IrI species, indicate upon completion catalysis, multinuclear Ir polyhydrides are not formed. This consistent hypothesis immobilization organometallic species on surface prevents bimolecular decomposition pathways. Immobilization homogeneous fragment represents unique simple strategy TON longevity catalyst.

Language: Английский

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Promoting Ethylene (co)Polymerization in Aliphatic Hydrocarbon Solvents Using tert‐Butyl Substituted Nickel Catalysts

Chinese Journal of Chemistry, Journal Year: 2021, Volume and Issue: 40(2), P. 215 - 222

Published: Oct. 26, 2021

Comprehensive Summary In the past few decades, development of high‐performance catalysts has been a key driving force and center research efforts in field olefin polymerization. However, major discrepancy exists between industrial researches which utilize aliphatic hydrocarbon solvents, academic predominantly focus catalytic properties aromatic solvents. this contribution, novel diaryl‐methyl aniline bearing eight tert ‐butyl groups was prepared subsequently transformed to four different kinds imine‐type ligands. The corresponding nickel complexes as well their counterparts derived from diphenyl‐methyl without were investigated ethylene multiple enable great solubility metal leading similar polymerization comparing with contrast, demonstrate significant solvent effect. Moreover, ligand electronic steric effects induced by lead thermal stability (up 140 o C) capabilities generating high molecular weight polymer copolymer products. This strategy can be potentially applied many catalyst systems help bridge studies practical applications.

Language: Английский

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Molecular Catalyst Synthesis Strategies to Prepare Atomically Dispersed Fe-N-C Heterogeneous Catalysts

Journal of the American Chemical Society, Journal Year: 2022, Volume and Issue: 144(41), P. 18797 - 18802

Published: Oct. 10, 2022

We report a strategy to integrate atomically dispersed iron within heterogeneous nitrogen-doped carbon (N-C) support, inspired by routes for metalation of molecular macrocyclic complexes. The N-C derived from pyrolysis ZIF-8 metal–organic framework, is metalated via solution-phase reaction with FeCl2 and tributyl amine, as Brønsted base, at 150 °C. Fe active sites are characterized 57Fe Mössbauer spectroscopy aberration-corrected scanning transmission electron microscopy. site density can be increased selective removal Zn2+ ions the support prior metalation, resembling transmetalation commonly employed preparation Fe-macrocycles. utility this approach validated higher catalytic rates (per total Fe) these materials relative established Fe-N-C catalysts, benchmarked using an aerobic oxidation reaction.

Language: Английский

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