Yazar "Doustkhah, Esmail" seçeneğine göre listele

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    Feeble Single-Atom Pd Catalysts for H2 Production from Formic Acid
    (Amer Chemical Soc, 2024) Doustkhah, Esmail; Tsunoji, Nao; Mine, Shinya; Toyao, Takashi; Shimizu, Ken-ichi; Morooka, Tetsuro; Masuda, Takuya
    Single-atom catalysts are thought to be the pinnacle of catalysis. However, for many reactions, their suitability has yet to be unequivocally proven. Here, we demonstrate why single Pd atoms (Pd-SA) are not catalytically ideal for generating H-2 from formic acid as a H-2 carrier. We loaded Pd-SA on three silica substrates, mesoporous silicas functionalized with thiol, amine, and dithiocarbamate functional groups. The Pd catalytic activity on amino-functionalized silica (SiO2-NH2/Pd-SA) was far higher than that of the thiol-based catalysts (SiO2-S-Pd-SA and SiO2-NHCS2-Pd-SA), while the single-atom stability of SiO2-NH2/Pd-SA against aggregation after the first catalytic cycle was the weakest. In this case, Pd aggregation boosted the reaction yield. Our experiments and calculations demonstrate that Pd-SA in SiO2-NH2/Pd-SA loosely binds with amine groups. This leads to a limited charge transfer from Pd to the amine groups and causes high aggregability and catalytic activity. According to the density functional calculations, the loose binding between Pd and N causes most of Pd's 4d electrons in amino-functionalized SiO2 to remain close to the Fermi level and labile for catalysis. However, Pd-SA chemically binds to the thiol group, resulting in strong hybridization between Pd and S, pulling Pd's 4d states deeper into the conduction band and away from the Fermi level. Consequently, fewer 4d electrons were available for catalysis.
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    Photocatalytic performance of disordered titanium-based hollow nanosheet metal-organic frameworks in wastewater treatment
    (Elsevier, 2024) Hassandoost, Ramin; Khataee, Alireza; Doustkhah, Esmail
    Background: The low long-range order in the crystallinity of metal-organic frameworks (MOFs), commonly known as disordered MOFs, can lead to critical property variations. However, controlling the synthesis conditions for a reproducible outcome is somehow cumbersome, especially if this control is accompanied by morphology engineering to be utilized in photocatalysis where band structure, band gap, surface area, and porosity matter. Methods: Here, we report a crystal and structure-directing approach for the morphology engineering of NTU-9-like MOF aggregated particles (Ti-DHTA(AP)) (composed of Ti4+ and 2,5-dihydroxyterephthalic acid (DHTA)) into a hollow nanosheet (Ti-DHTA(HNS)) morphology. Triethylamine (TEA), here, acts as a structure-directing agent (SDA), and monodispersed polystyrene (PS) as a hard template. The three obtained Ti-DHTAs were eventually investigated in the photocatalytic removal of organic contaminants (dye and pharmaceuticals) and comprehensively characterized by (photo)electrochemical approaches. Significant Findings: The hollow nanosheet-architected Ti-DHTA(HNS) with a superior photocatalytic activity than the other morphologies also exhibits an overall photocatalytic removal (synergic adsorption-photodegradation) of similar to 6.5-fold higher than the commercial TiO2 (P25) under the visible light irradiation, with a degradation turnover (dTON) of 27 mmol h(-1) g(cat)(-1). Ti-DHTA(HNS) also shows promising results in the photocatalytic removal of dye and pharmaceutical wastewater. Photoelectrocatalytic characterizations were provided to compare the photocatalytic performance of synthesized Ti-DHTAs (e.g., in cyclic chronoamperometry (CA), 6-fold higher photoresponse than Ti-DHTA(AP)). Nyquist plots further exhibit that the charge transfer resistance (R-ct) of the unmodified Ti-DHTA(AP) is similar to 10-fold higher than Ti-DHTA(HNS) under visible light illumination. Furthermore, the actual water samples and the reusability of Ti-DHTA(HNS) were investigated. The addition of the radical scavenger agent can confirm the presence of varoius active radicals during the degradation, and hence, the formation of hydroxyl radicals was probed by adding o-phenylenediamine as a trapping agent. During methylene blue (MB) photodegradation, the LC-MS analysis exhibits acetoacetic acid formation (m/z = 102.03) as the dominant intermediate.
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    Structural diversity and tetrel bonding significance in lead(ii) complexes with pyrazoylisonicotinoylhydrazone and varied anionic co-ligands
    (Royal Soc Chemistry, 2024) Mahmoudi, Ghodrat; Garcia-Santos, Isabel; Fernandez-Vazquez, Roi; Gomila, Rosa M.; Castineiras, Alfonso; Doustkhah, Esmail; Zangrando, Ennio
    Four lead(ii) complexes featuring pyrazoylisonicotinoylhydrazone ligand paired with various anionic co-ligands (azido, thiocyanato, nitrito, and nitrato) were synthesized and thoroughly examined using structural, analytical, and spectroscopic techniques. These ligands, in their mono-deprotonated state, bind to the lead(ii) ion in a tridentate manner through two nitrogen atoms and one oxygen atom. Single-crystal X-ray crystallography revealed the capacity of these molecular complexes to form larger aggregates influenced by the nature of the anion attached to the metal center. In every complex, the lead atom adopts a hemidirectional coordination environment, making it geometrically suited for tetrel bond formation. The crystal structures demonstrate that lead atoms engage in notably short interactions with nitrogen atoms, distances that are shorter than the sum of their van der Waals radii yet exceed the sum of their covalent radii. These tetrel bonds play a pivotal role in weaving the monomeric into self-assembled dimers or extended supramolecular 1D polymers. The formation and characteristics of these intriguing supramolecular structures observed in the solid state of each complex were further explored and validated through density functional theory (DFT) calculations and several computational tools like MEP, NCIPlot, QTAIM, and ELF methods.