Multiscale Models in Heterogeneous Catalysis: Incorporating Dynamics into Reaction Kinetics

Modern operando spectroscopy and microscopy, and kinetic investigations have provided qualitative evidence for active site dynamics, catalyst surface dynamics, and charge transport. On the macroscale, intraparticle and interparticle mass and heat transfer can be tuned to optimise selectivity over heterogeneous catalysts. On the microscale, adsorbate-induced restructuring, adsorbate mobility, surface composition, oxidation states, charge transport, bandgap, and the degree of coordination of the active site have been identified for controlling product selectivity. There exist, however, limited physics-based and data-driven multiscale models that can assimilate these qualitative descriptors in an integrated manner to extract quantitative catalyst activity, stability, and product selectivity descriptors. A multiscale model, which describes the evolution of gas species, adspecie accumulation due to reactivity, stability, lifetime, and mobility, charge transport involving electrons and holes, heat transfer for non-isothermal conditions due to reaction exothermicity, and the changing catalyst states is provided. Dynamical effects are included in these models to bridge the gap between laboratory-scale studies and industrial technical reactors.

Ligand-Tuning of the Stability of Pd(II) Conjugates with Cyanocobalamin

Besides the well-known functions performed by vitamin B12 (CblCN) in biochemical processes of the human body, an increasing interest has been raised by the possibility of its use as a transmembrane drug carrier, capable, among others, of enhancing the accumulation of inorganic cytostatics in cancer cells. The present study was aimed at determining the possibility of the formation of CblCN conjugates with Pd(II) complexes. A key aspect was their stability, which we attempted to tune by appropriate choice of ligands. Syntheses, spectroscopic analysis of postreaction systems and kinetic investigations of conjugate formation reactions, have been complemented by DFT modelling. The obtained results showed that ligand charge, geometry and electron affinity may have a significant impact on carrier binding and release leading to the activation of the Pd(II) complex. This provides a rationale to expect that with appropriate composition of the coordination sphere, it will be possible to extend the spectrum of less toxic inorganic chemotherapeutics.

Desulfurization of liquid fuels using aluminum modified mesoporous adsorbent: towards experimental and kinetic investigations

In this study, a modified mesoporous adsorbent (MSU-S) impregnated by aluminum was used to remove the aromatic sulfur compounds from n-decane as the model fuel. Physical and chemical properties of as-synthesized adsorbent were investigated by XRD (X-Ray Diffraction), SEM (Scanning Electron Microscopy), FTIR (Fourier Transform Infrared spectroscopy) and BET (Brunauer–Emmett–Teller) method. Adsorptive desulfurization of model fuel was studied through batch and continues processes under mild temperature and normal atmospheric pressure. The equilibrium adsorption was modeled by Langmuir, Temkin, and Freundlich and the kinetics of adsorption was studied through first, second and intraparticle diffusion models. It was figured out that Temkin and the pseudo-second-order model were best fitting the adsorption equilibrium and describing the kinetics, respectively.

Ligand-Metal Charge Transfer Induced via Adjustment of Textural Properties Controls the Performance of Single-Atom Catalysts During Photocatalytic Degradation

Because of their peculiar nitrogen-rich structure, carbon nitrides are convenient polydentate ligands for designing single-atom-dispersed photocatalysts. However, the relation of catalysts textural properties with their photophysical properties and as a result activity in photocatalytic applications is rarely elaborated. Herein we report the preparation and characterization of a series of single-atom heterogeneous catalysts featuring highly-dispersed Ag and Cu species on mesoporous graphitic C₃N₄. We show that adjustment of materials textural properties and thereby metal single atoms coordination mode enables ligand-to-metal (LMCT) or ligand-to-metal-to-ligand charge transfer (LMLCT), a property tha was long speculated in single-atom catalysis but never observed. We employ the developed materials in the degradation of organic pollutant under irradiation with visible light. Kinetic investigations under flow conditions show that single atoms of Ag and Cu decrease the amount of toxic organic fragmentation products, while leading to a higher selectivity towards full calcination. The results correlate with the selected mode of charge transfer in the designed photocatalysts and provide a new understanding of the surface state of single-atom catalysts. The concepts can be exploited further to rationally design and optimize other single-atom materials.

Ligand-Metal Charge Transfer Induced via Adjustment of Textural Properties Controls the Performance of Single-Atom Catalysts During Photocatalytic Degradation

Because of their peculiar nitrogen-rich structure, carbon nitrides are convenient polydentate ligands for designing single-atom-dispersed photocatalysts. However, the relation of catalysts textural properties with their photophysical properties and as a result activity in photocatalytic applications is rarely elaborated. Herein we report the preparation and characterization of a series of single-atom heterogeneous catalysts featuring highly-dispersed Ag and Cu species on mesoporous graphitic C₃N₄. We show that adjustment of materials textural properties and thereby metal single atoms coordination mode enables ligand-to-metal (LMCT) or ligand-to-metal-to-ligand charge transfer (LMLCT), a property tha was long speculated in single-atom catalysis but never observed. We employ the developed materials in the degradation of organic pollutant under irradiation with visible light. Kinetic investigations under flow conditions show that single atoms of Ag and Cu decrease the amount of toxic organic fragmentation products, while leading to a higher selectivity towards full calcination. The results correlate with the selected mode of charge transfer in the designed photocatalysts and provide a new understanding of the surface state of single-atom catalysts. The concepts can be exploited further to rationally design and optimize other single-atom materials.

Ligand-Metal Charge Transfer Induced via Adjustment of Textural Properties Controls the Performance of Single-Atom Catalysts During Photocatalytic Degradation

Because of their peculiar nitrogen-rich structure, carbon nitrides are convenient polydentate ligands for designing single-atom-dispersed photocatalysts. However, the relation of catalysts textural properties with their photophysical properties and as a result activity in photocatalytic applications is rarely elaborated. Herein we report the preparation and characterization of a series of single-atom heterogeneous catalysts featuring highly-dispersed Ag and Cu species on mesoporous graphitic C₃N₄. We show that adjustment of materials textural properties and thereby metal single atoms coordination mode enables ligand-to-metal (LMCT) or ligand-to-metal-to-ligand charge transfer (LMLCT), a property tha was long speculated in single-atom catalysis but never observed. We employ the developed materials in the degradation of organic pollutant under irradiation with visible light. Kinetic investigations under flow conditions show that single atoms of Ag and Cu decrease the amount of toxic organic fragmentation products, while leading to a higher selectivity towards full calcination. The results correlate with the selected mode of charge transfer in the designed photocatalysts and provide a new understanding of the surface state of single-atom catalysts. The concepts can be exploited further to rationally design and optimize other single-atom materials.