Molecular Catalysis最新文献

Selective hydrogenolysis of C_Ar-O bonds in lignin to produce aromatic compounds typically necessitates severe conditions. We developed a Ni/Nb₂O₅HZSM-5 catalyst that facilitates direct cleavage of guaiacol's aryl ether bonds at reduced temperatures (200 °C) and pressure (0.1 MPa H₂), achieving a conversion of 89.5 % with the selectivity of phenol at 81.7 %, while retaining its activity after five cycles. The Ni/Nb₂O₅HZSM-5 exhibits a higher yield of phenol (49.1 mmol_phenol·g_Ni⁻¹·h⁻¹), currently achieving the highest phenol yield among Ni-based catalysts. The addition of Nb₂O₅ enhances the dispersion of Ni and augments the effective surface area. In addition, the strong interaction of Nb with the HZSM-5 changed the electronic state of Nb and enhanced the resistance of the catalyst to high temperature and mechanical stress. Employing this catalyst for lignin depolymerization in an aqueous medium led to a 17.0 wt% yield of alkyl phenolic compounds. This approach represents an advancement in biomass resource conversion, circumventing the dependency on high-pressure and precious-metal catalysts, and signaling a new trajectory for sustainable biomass utilization in scientific research.

Herein, we report a combination of experimental and computational studies for the photochemical synthesis of N,N’-dibenzyl-N-methylamine via three component coupling of benzylamine, benzaldehyde, and CO₂ assisted by 1-butyl-3-methylimidazolium chloride ionic liquid at atmospheric pressure. The theoretical investigation revealed the formation of imine and two reaction intermediates (I & II) through the coupling reaction of CO₂ with benzaldehyde and benzylamine in excess phenyl saline. The Molecular electrostatic potential and activation energy calculations depicted the formation of Intermediate I (formoxysilane) formation by inserting CO₂ into the SiH bond of the phenyl silane via hydrogen bonding. Furthermore, Intermediate I converted to Intermediate II by reacting with phenyl saline (PhSiH₃) and imine, followed by the final methylated product via the CN bond between the carbon of CO₂ and nitrogen of the imine group.

Synthesizing efficient and selective green ideal catalysts has been an increasingly critical, yet unsolved, issue for the ammonia synthesis industry, hindering the growing global demand for environmental protection and energy efficiency. Electrocatalytic nitrogen reduction reaction (eNRR) is a promising technology for low-energy ammonia synthesis. However, designing efficient electrocatalysts for NRR remains challenging. The emergence of graphene-like substrates offers exciting prospects for addressing this challenge and facilitating single-atom catalysts in eNRR. Here, we report the innovative selection of a recently synthesized two-dimensional biphenyl network (2D BPN) compound as a substrate. Its excellent conductivity and porosity enable stable transition metal atoms (TMs) support for constructing eNRR electrocatalysts. we evaluated the feasibility of 23 TMs anchored on BPN for eNRR by high-throughput first-principles calculations. Through a systematic five-step strategy, we identified several single-atom catalysts (SACs) with potential for eNRR, including Mo@BPN, V@BPN, W@BPN, and Re@BPN. Among them, Mo@BPN exhibited the best balance in the adsorption of key reaction intermediates (e.g., N₂H and NH₃) and demonstrated a low limiting potential (-0.37 V). In addition, the underlying mechanism of NRR activity was elucidated by analyzing the extrinsic patterns revealed through the screened catalysts. A triangular volcano diagram, incorporating the initial protonation step, adsorption free energy, and final protonation step, revealed the NRR activity trend. Overall, this study provides a solid theoretical foundation and valuable guidance for future experimental exploration of efficient electrocatalysts for ammonia synthesis on BPN. Crucial insights into the theoretical design of efficient electrocatalysts are also offered.

This study investigates the application of cobalt-copper layered double hydroxides (LDHs) in the oxidation of butylated hydroxytoluene (BHT) and explores their catalytic behavior during thermal treatment. LDHs were synthesized via coprecipitation, and various ratios of Co-Cu hydrotalcite were subjected to thermal treatment. Structural analysis revealed that thermal treatment transforms the LDHs into mixed metal oxides. Among the synthesized catalysts, Co1Cu3-LDHs exhibited superior catalytic activity in the oxidation of BHT. Techniques such as XRD, FT-IR, TGA, N₂ adsorption-desorption, SEM, and XPS were employed to investigate the structural changes and surface properties of the LDHs. The Co1Cu3-LDH catalyst, treated at 250 °C, exhibited outstanding catalytic performance, attributed to the synergistic effects between Co and Cu. Upon optimizing the reaction conditions, the conversion of BHT reached 99 %, with a selectivity of 77 % towards 3,5-di‑tert‑butyl‑4-hydroxybenzaldehyde (BHT-CHO). The oxidation mechanism involves the oxidation of the π-electron system on the benzene ring and deep oxidation of the phenolic hydroxyl methyl group, with two potential reaction pathways proposed.

In order to get a better life, industrial revolution prevails worldwide since past few centuries but the rapid growth of industrialization in our planet invites different type of severe pollutions and hence environmental damage, which has now impacted on the survival of mankind. Although, the survival of mankind demands physical resourses but these are limited in quantity. In this problematic situation, biomimetics can be a solution. Biomimetics is the study which deals with nature and natural phenomenon to investigate the fundamental mechanisms, and afterwards to apply the concepts in the field of science, technology, and vastly in medical. In this present study, we look into one of the biomimetic enzymes, phenoxazinone synthase. Phenoxazinone synthase is an important class of enzyme that catalyzes the oxidation of o-aminophenol to aminophenoxazinone with the activation of molecular dioxygen. Bioinorganic chemists are largely influenced by the nature's design on phenoxazinone synthase and hence they are excited to synthesize this mimics model enzyme to understand the mechanistic pathways properly, so that they can explored its potential applications in the field of bioelectronics, material science, optoelectronics, and biomedical. In the literature, a significant number of Schiff base bound model complexes (about 126) for phenoxazinone synthase-like activity have been synthesized and catalytically characterized by different research groups. A variety of Schiff base ligands (about 68) are employed to prepare such model complexes with different nuclearities in presence of one or more 3d metals like V, Mn, Fe, Co, Ni, Cu and Zn in order to modulate the catalytic activity and to get a better structure property relationship on phenoxazinone synthase activity. This article aims to explore the recent advances, challenges, and opportunities in bioenzymatic catalysis, highlighting its promise to revolutionize the way we create value added compounds and materials.

Bimetallic or polymetallic materials often exhibit different catalytic activities due to the interaction between different metal centers compared with monometallic materials. Here, we designed and synthesized a new bimetallic catalyst SnMo-MOF with tin and molybdenum as metal centers by solvothermal synthesis, which could realize the oxidation of diphenyl sulfide (Ph₂S) and difurfuryl sulfide (FFS) under mild conditions, and selectively generate sulfoxide and sulfone, respectively. The introduction of Sn enhanced the Lewis acidity of the catalyst surface and the electron transfer between Sn and Mo led to bimetallic synergistic catalysis, which made a great contribution to the high conversion and selectivity of sulfide oxidation. This is reflected in the complete conversion of Ph₂S and FFS with 91.8% and 98.1% selectivity of diphenyl sulfoxide (Ph₂SO) and difurfuryl sulfone (FFSO₂), respectively. The composite material had good substrate adaptability for the catalytic oxidation of other phenyl sulfides and furfuryl sulfides, which opens interesting prospects for the development of new MOF materials as efficient heterogeneous catalysts for the oxidation of thioethers.

As an environmentally friendly way, propylene epoxidation forming propylene oxide (PO) catalyzed by Ag-based catalyst had received considerable attentions, which was important in the chemical industry. The experimental results exhibited that the products of propylene epoxidation catalyzed by Ag₂O were PO and carbon dioxide. In this work, the spin-polarized density functional theory (DFT) calculations combined with a Hubbard U correction were performed to investigate propylene epoxidation on Ag₂O(111) and Cl−Ag₂O(111) surfaces, and reaction micro-mechanism of propylene epoxidation was discussed in detail. The micro-mechanism mainly included two pathways: the allylic hydrogen stripping (AHS) pathway and the intermediary propylene oxametallacycles (OMMP) pathway. In the AHS pathway, the allyl radical can be generated, which was considered as a precursor for acrolein formation, and completed combustion yielding CO₂. In the OMMP pathway, PO, propanal and acetone can be created through the propylene oxametallacycle intermediates. Our calculated results indicated that the O_suf site on the Ag₂O(111) surface has a stronger basicity than the O_suf site on the Cl−Ag₂O(111) surface, the stronger basicity was beneficial for the AHS pathway, and carbon dioxide can be regarded as the main product for propylene epoxidation. It was also found that PO became the main product with the effect of Cl doping on the Ag₂O(111) surface, and the electrostatic effect of Cl−Ag_cus can improve the adsorption ability between the Ag_cus site and the absorbate. Moreover, energetic span model analysis were carried out and found that the TOF or the orders of selectivity are: acrolein > acetone > propanal ≅ PO on clean surface, PO > acetone > acrolein > propanal on the Cl doped surface, and acrolein, as a precursor, was easily completely burned to CO₂, the results confirmed that the selectivity of PO can be enhanced by the effect of subsurface Cl^- doping. The present study aimed to help workers to find high selectivity and activity catalyst for propylene epoxidation.