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In this paper, we compare the reactivity of a series of triaryl borates B(OArx)3 as catalysts for the hydroboration of alkenes and alkynes. It was observed that commercially available B(OPh)3 performed the poorest, whereas catalysts with o-F atoms appeared to perform much better. [ABSTRACT FROM AUTHOR]

The availability of catalytic sites for contact with reactants is a key issue to improve the performance of a catalyst, where constructing hollow structured nanomaterials has been considered as an effective strategy. Here, an N-doped carbon supported Ru catalyst with an interior cavity was synthesized by etching a MOF-derived core–shell precursor, in which metal Ru can be highly dispersed in the porous shell. This catalyst shows 98.7% conversion and >99% selectivity towards p-chloroaniline in the hydrogenation of p-chloronitrobenzene, which is better than the corresponding supported catalyst. Moreover, it also displays excellent stability with 5 cycle runs and good substrate universality for the hydrogenation of extensive substituted nitroarenes. Various characterization techniques and control experiments reveal the advantage of the unique structure to promote the mass transport and adsorption of reactant molecules on Ru sites. This work provides a novel strategy to design an efficient Ru-based catalyst for chemoselective hydrogenation. [ABSTRACT FROM AUTHOR]

A new method for the generation of benzyl radicals from terminal aromatic alkynes has been developed, which allows the direct cross coupling with acrylate derivatives. Our additive-free protocol employs air-stable diamino Mo3S4 cubane-type cluster catalysts in the presence of hydrogen. A sulfur-centered cluster catalysis mechanism for benzyl radical formation is proposed based on catalytic and stoichiometric experiments. The process starts with the cluster hydrogen activation to form a bis(hydrosulfido) [Mo3(μ3-S)(μ-S)(μ-SH)2Cl3(dmen)3]+ intermediate. The reaction of various aromatic terminal alkynes containing different functionalities with a series of acrylates affords the corresponding Giese-type radical addition products. [ABSTRACT FROM AUTHOR]

The synthesis of three N-heterocyclic carbene complexes by stepwise grinding is described in this paper. The benzimidazolium salts ([H2L]Br2 and [H2L](PF6)2 ([H2L] = 1,1′-di(2-picolyl)-3,3′-methylenedibenzoimidazolium)) were initially prepared. Their reactions with Ni(OAc)2·4H2O by grinding afforded three nickel complexes, [NiL]Br2·CH3OH (1), [NiL]Br2·2H2O (1′) and [NiL](PF6)2·0.5CH3CN (2), respectively. A five-coordinated complex [NiLBr]PF6 (3) was further obtained by grinding NH4PF6 with complex 1 or 1′, or grinding KBr with complex 2. Complex 3 can also be obtained by direct grinding of complexes 1/1′ and 2. Complex 3 was subsequently used as a catalyst in the C–S bond cross-coupling of 2-bromoacetophenone and 2-mercaptobenzothiazole. The entire procedure from the synthesis to the catalytic reaction was performed by mechanochemistry. The green metrics E-factor and EcoScale close to ideal values showed the eco-friendly nature of the entire procedure. [ABSTRACT FROM AUTHOR]

Proton exchange membrane water electrolysis (PEMWE) can be coupled with renewable energy power generation technology and is considered to be a highly promising hydrogen production technology. However, the acidic electrolyte environment, as well as the numerous sulfonic acid groups on the proton exchange membrane surface, can seriously corrode the oxygen evolution reaction (OER) catalyst and even cause deactivation. To develop an efficient acidic OER catalyst, the IrOx/WO3 heterostructure OER catalyst was prepared by a hydrothermal-calcination method. The coordination environment of IrOx was regulated through the electronic rearrangement effect, improving the OER activity and stability of the catalyst in acidic media. The prepared IrOx/WO3 exhibits excellent OER activity in 0.5 M H2SO4, with an overpotential of only 260 mV to achieve a current density of 10 mA cm−2 and a mass activity of 176.8 A gIr−1. It can stably operate for over 12 hours at a current density of j = 10 mA cm−2. [ABSTRACT FROM AUTHOR]

Heterogenized molecular catalysts have shown interesting activities in different chemical transformations. In our previous studies, a molecular catalyst, Re(bpy)(CO)3Cl where bpy is 2,2′-bipyridine, was covalently attached to silica surfaces via an amide linkage for use in photocatalytic CO2 reduction. Derivatizing the bpy ligand with electron-withdrawing amide groups led to detrimental effects on the catalytic activity of Re(bpy)(CO)3Cl. In this study, an alkyl amine linkage is utilized to attach Re(bpy)(CO)3Cl onto SiO2 in order to eliminate the detrimental effects of the amide linkage by breaking the conjugation between the bpy ligand and the amide group. However, the heterogenized Re(I) catalyst containing the alkyl amine linkage demonstrates even lower activity than the one containing the amide linkage in photocatalytic CO2 reduction. Infrared studies suggest that the presence of the basic amine group led to the formation of a photocatalytically inactive Re(I)-OH species on SiO2. Furthermore, the amine group likely contributes to the stabilization of a surface Re(I)-carboxylato species formed upon light irradiation, resulting in the low activity of the heterogenized Re(I) catalyst containing the alkyl amine linkage. [ABSTRACT FROM AUTHOR]

The present investigation presents a facile approach for synthesizing cobalt nanoparticles encapsulated in nitrogen-doped graphite (Co@NC) for catalytic purposes. The Co@NC composite was employed for the conversion of 4-nitrophenol to 4-aminophenol. Despite the extensive research conducted on the catalytic efficacy of transition metal catalysts, the examination of the cobalt catalyst's durability and reusability over successive reaction cycles remains unexplored. A Co@NC composite catalyst was synthesized using innovative precursors of glucose, urea, and cobalt nitrate. The results demonstrate that the high specific surface area and pore structure of the Co@NC composite catalyst not only have a high adsorption capacity but also accelerate the rate of electron transfer. Due to the synergistic effects of cobaltic metal and nitrogen-doped graphite, the Co@NC catalyst displays remarkable catalytic effects comparable to those of noble metal catalysts. The stable 92% 4-NP conversion rate after 10 reaction cycles also demonstrated the reusability of the composite catalyst. The Co@NC composite catalyst possesses a number of noteworthy characteristics, including excellent recyclability, high stability, and easy magnetic recovery. These characteristics make it a promising option for practical applications in the removal of 4-nitrophenol from industrial water. [ABSTRACT FROM AUTHOR]

In this study, we present a colloidal assembly of histidyl bolaamphiphiles whose imidazoles coordinate with rhodium ions (HisC7[Rh]) to exhibit catalytic isomerization activity for cis-stilbene and cis-alkene molecules. The histidyl bolaamphiphiles self-assemble to form a soft scaffold that functions analogously to an apoenzyme. This scaffold exposes multiple histidyl imidazoles and carboxylates on its surface, to which rhodium ions bind, generating catalytically active sites. The Rh coordination with the biochemical functional groups was verified through comprehensive vibrational spectroscopy and calorimetry. The colloidal HisC7[Rh] demonstrated a significant catalytic effect on the isomerization of cis- to trans-stilbene under mild H2 conditions, resulting in 69% yield of trans-stilbene. In contrast, when Rh(cod)2BF4 was employed as a control catalyst, only the hydrogenated products of bibenzyl were obtained. These findings underscore the crucial role of histidyl motifs in exhibiting unique catalytic isomerization activity through the coordination with Rh. The catalytic activity of HisC7[Rh] is governed by several factors, such as rhodium content, solvent composition, temperature, and H2 pressure. Moreover, HisC7[Rh] displayed moderate isomerization activity towards not only stilbene but also unsaturated fatty acid isomers, highlighting its expansive potential as an isomerization catalyst. [ABSTRACT FROM AUTHOR]

An effective combination of polyoxometalates (POMs) and porous materials is a feasible method to solve the homogeneity of POMs and synthesize extremely stable POM-based catalysts. Herein, by using simple mechanochemical synthesis, we fabricated a series of composites constructed by Keggin-POMs, p-phenylenediamine (Pa-1), and 1,3,5-triformylphloroglucinol (Tp), which in situ form a stable covalent organic framework (Keggin-POMs@TpPa-1). Notably, the different Keggin-POMs@TpPa-1 composites showed different catalytic effects on thioether oxidation reaction under mild conditions. From the comparison, the catalytic effect of PW12@TpPa-1 with its added amount of 27% H3PW12O40 is superior to that of other composites, whose catalytic efficiency can reach 99%. This study provides some inspiration for designing diverse POM-modified catalysts with outstanding stability and efficiency using COFs as supports. [ABSTRACT FROM AUTHOR]

It is necessary to design and develop simpler, more efficient, and cleaner synthetic methodologies to prepare increasingly complex molecules. One interesting strategy is multicatalysis. The aim of this study was to synthesize a multicatalytic hybrid system by the immobilization of H3PW12O40 (HPW), a polyoxometalate, on ionic liquid-functionalized mesoporous silica (SBA-15 or MCF). The resulting catalysts were characterized by different techniques, including N2 adsorption–desorption, Boehm titration of the acid site, SEM-EDS, FT-IR, XPS, CP-MAS, and NMR. To test the active site acid-oxidant duality of HPW, 2-pyridones were synthesized in a one-pot methodology with auto-tandem catalysis involving the ring-opening/ring-closure/oxidation sequence of 4H-pyrans. The morphology of the support structure affects the duality of HPW. Whereas the MCF complex favors oxidation, the SBA-15 complex favors Brønsted acidity (finding greater oxidation when adding water). The hybrid catalyst was recovered and reused for eight consecutive reaction cycles with no significant loss in activity. [ABSTRACT FROM AUTHOR]

The electrochemical reduction of CO2 (ERCO2) into economically valuable chemicals is one of the most promising ways to achieve carbon neutrality. Perovskite materials have shown potential applications in high-temperature catalysis and photocatalysis due to their unique structure, but their catalytic performance during the aqueous ERCO2 has rarely been investigated. In this study, we developed an efficient YbBiO3 perovskite catalyst (YBO@800) for CO2 conversion to formate, with a maximum faradaic efficiency of 98.3% at −0.9 VRHE, as well as a considerable faradaic efficiency (>90%) over a wide potential range (from −0.8 to −1.2 VRHE). Further analyses demonstrated that the structural evolution of YBO@800 occurred during the ERCO2 process, and the subsequent construction of the Bi/YbBiO3 heterostructure played a significant role in optimizing the rate-determining step of the ERCO2. This work inspires the development of perovskite catalysts for the ERCO2 and provides insight into the influence of the surface reconstruction of catalysts on their electrochemical performance. [ABSTRACT FROM AUTHOR]

Besides adjusting the active sites, modulating the adsorption capacity and diffusion ability can realize the enrichment of the antibiotics and propel the catalytic degradation properties via the effective contact between active species and antibiotics. Herein, a series of CoS2@MMT were prepared by a two-step synthesis. With the synergy of adsorption and catalysis, the obtained composites exhibit potential for the rapid and effective degradation of ofloxacin (OFL) as advanced oxidation process (AOP) catalysts by activating peroxymonosulfate (PMS). Among them, 10CoS2@MMT can adsorb 41% of OFL and its total removal efficiency of OFL can reach 96.7% within 10 min. Based on the related tests, the composite can decompose OFL through both radical (˙OH, SO4˙−, and O2˙−) and non-radical pathways (1O2). The satisfactory catalytic properties and the stability of this kind of composite demonstrate their potential in the practical application of water decontamination. [ABSTRACT FROM AUTHOR]

Metal–ligand cooperation (MLC) catalysis is one of the most important concepts in the field of organometallic catalysis. However, diverse functional ligands result in ambiguous mechanisms and constrain the understanding of MLC catalysis. Herein, a theoretical study based on DFT calculations is performed to shed light on the mechanistic preference of borrowing-hydrogen N-alkylation catalysed by a ruthenium complex with dual proton-responsive sites. The results suggest that the reaction pathway mediated by the α-NH site requires overcoming a higher activation energy barrier (31.4 kcal mol−1) compared with the γ-NH site due to the ligand distortion after protonation. Nevertheless, the instability caused by the ligand distortion does not transform into catalytic activity for the subsequent hydrogenation reaction. In contrast, the γ-NH site facilitates the rate-determining hydride transfer step (21.1 kcal mol−1) via non-covalent interaction instead of participating in the bond formation and breaking process, which is found to be a more plausible mechanism. These findings demonstrate the versatile role of ligand N–H functionality, which may provide useful guidance for the design of new MLC catalysts in the future. [ABSTRACT FROM AUTHOR]

Three biacidic tin-based functional ionic liquid catalysts were prepared, including [HO3S-(CH2)3-mim]Cl-SnCl4, [HOOC-(CH2)2-mim]Cl-SnCl4, and [HO-(CH2)2-mim]Cl-SnCl4. A Fourier transform infrared (FT-IR) spectrometer, a nuclear magnetic resonance instrument (1H NMR), an X-ray diffractometer (XRD), and a thermal gravimetric analyzer (TGA) were used to test and analyze the structures, molecular structure, crystal structures, and thermal performance of the three catalysts. And investigate their performance in catalyzing the coupling reaction between ethylene carbonate (EC) and dimethyl succinate (DMSu) to synthesize poly(ethylene succinate) (PES). Orthogonal tests were performed to optimize process parameters, explore the effect of polycondensation temperature on the intrinsic viscosity number ([η]) of PES, and discuss the effect of acidic groups on catalytic performance and the mechanism of the catalytic action. An FT-IR spectrometer and a TGA were used for structural characterization and thermal performance tests on polymer PES, and biodegradability tests (enzymolysis tests) on PES. The results showed that the three biacidic tin-based functional ionic liquid catalysts prepared in this study had a satisfactory catalytic effect. Among them, the sulfonic acid imidazole tin-based ionic liquid catalyst ([HO3S-(CH2)3-mim]Cl-SnCl4) manifested the best catalytic performance. The catalytic mechanism of the biacidic tin-based ionic liquid catalysts was further explained and discussed. Under the optimal process conditions for the transesterification reaction (temperature: 227 °C; material ratio: EC : DMSu = 1; catalyst consumption: 1.0 wt%; time: 5.5 h), PES had a yield of 67.12%, a selectivity of 82.47%, and an intrinsic viscosity number of [η] = 1.052 dL g−1, and had good thermal stability and biodegradability. [ABSTRACT FROM AUTHOR]

Herein, a series of transition metal coordinated metalloporphyrin-mediated M–N–C catalysts with single and dual metal atoms were prepared and characterized. Interestingly, these M–N–C catalysts exhibit accelerated N2 reduction behaviors through electrochemical catalysis. At the potential of E = −0.4V (vs. RHE), the optimum catalyst Fe0.95Ni0.05TPP@rGO-800 shows excellent catalytic activity, and the NH3 yield is 22.5 μg mgcat−1 h−1, which is much higher than that of its single metal counterparts alone, and the faradaic efficiency is as high as 50.7%, which is better than those of most reported catalysts. These results provide an opportunity to further explore the efficient electrochemical synthesis of NH3 from M–N–C materials in the future. [ABSTRACT FROM AUTHOR]

The traditional one-step reaction of methanol to aromatics on ZSM-5 is a potential route for the synthesis of non-petroleum aromatics. Zn/ZSM-5 is widely used as the most common catalyst for the methanol to aromatics reaction. However, due to the generation of by-products such as alkanes, carbon atoms are consumed, and it is still difficult to obtain high aromatic selectivity. In this work, in order to improve the aromatic selectivity, the traditional one-step reaction is divided into two steps: methanol to light olefins and aromatization of light olefins. SAPO-34 and Zn/ZSM-5 are designed as catalysts for the above two-step reaction respectively. Through a study of the loading methods and loading ratios of the above two catalysts, it is found that the top-down loading mode of SAPO-34 and Zn/ZSM-5 can obtain higher aromatic selectivity than the one-step reaction. The reason for the improvement of aromatic selectivity is that the light olefins generated by SAPO-34, as the intermediate of methanol aromatization, promote the generation of aromatics on the Zn/ZSM-5 catalyst. The acidity and reaction temperature of the two catalysts are further optimized to improve the reaction performance. Under the conditions of 673 K and a loading ratio of SAPO-34 to Zn/ZSM-5 of 1 : 9, the selectivity of aromatics and BTX in the two-step reaction can reach 80.0% and 56.7% respectively. It is much higher than 64.9% and 32.0% in the one-step reaction by filling Zn/ZSM-5 only. This reaction method provides a new way for the production of aromatics and BTX and shows great development potential. [ABSTRACT FROM AUTHOR]

The energy release performance of energetic compounds like 3-nitro-1,2,4-trizole-5-one (NTO) and 5,5′-bistetrazole-1,1′-diolate (TKX-50) are indispensable in propellent formulations. However, thermal decomposition behavior is impeded by unfavorable catalysts. Presently, ultrathin porous MoS2 nanosheets (pMoS2) are considered as high-performance catalysts for NTO and TKX-50 decomposition. The pMoS2 in 5 wt% content could decrease the decomposition temperature of NTO and TKX-50 by 13.5 °C and 37.1 °C, respectively. Furthermore, the exothermic heat-release for pMoS2@NTO and pMoS2@TKX-50 were increased almost by a factor of two. The porous structure combined with large specific area of pMoS2 could mostly trigger the catalytic effect towards energetic compound decomposition. Additionally, the as-obtained MoS2 endowed advances in safety performance of NTO and TKX-50, with remarkably reduced impact and friction sensitivity. The as-proposed strategy may stimulate a different perspective towards the fast decomposition of energetic materials in propellants. [ABSTRACT FROM AUTHOR]

The selectivity of metal nanocatalysts is critical to chemical transformations and industries. Herein, a highly selective heterogeneous living cell catalytic system (LCCS) with intracellular Pd nanodots (bio-nPd) via in situ biomimetic synthesis is constructed. Research studies show that the LCCS is capable of size-selective catalytic hydrogenation for a series of acrylamides in water under mild conditions, and has self-reproducible, reusable and recyclable performance. Moreover, the LCCS also has high catalytic activity: the turnover frequency (TOF) for the acrylamide is up to 198.3 h−1 and the conversion rate is 100%. The calculation results show that the size-selectivity is closely interrelated with the inherent "gating" effect of the cell membrane, which is beneficial for the entry of small molecules. The highly selective and eco-friendly characteristics of the catalytic systems provide an effective strategy for exploring novel catalytic systems that can meet the requirements of sustainable development. [ABSTRACT FROM AUTHOR]

The problem of energy crisis promotes the development and utilization of materials related to the application of solar energy. Employing solar energy for clean photocatalytic nitrogen fixation is an effective approach to replace the high-energy consumption Haber–Bosch nitrogen fixation method to alleviate the energy crisis. In this article, mulberry-like BiVO4 containing oxygen vacancies (OVs–BVO) was prepared by the solvothermal method. In order to further elevate the catalytic effect of the catalyst, Ag nanoparticles with uniform distribution were loaded on the surface of OVs–BVO by the photodeposition method. A variety of survey techniques were performed to characterize the properties of the materials, including XRD, SEM, TEM, Raman, XPS, EPR, DRS, PL and Kelvin probe study. The results show that the subband (defect level) generated by the presence of OVs can accommodate low energy electrons to activate the adsorbed N2. Ag nanoparticles firmly attached on the surface of OVs–BVO produced a strong local surface plasmon resonance (LSPR) effect, which promoted the utilization of light energy and the effective separation of electron–hole pairs. The electrons have no interfacial barrier to overcome during the transfer between Ag and BVO due to their Ohmic contact. The application of Ag loaded OVs–BVO as a catalyst provides a new direction for the study of catalysts in the field of photocatalytic nitrogen fixation. [ABSTRACT FROM AUTHOR]

Imidazolium sulfonate zwitterions (ZIs) with unconventional counter-anions were used to fabricate a series of mesoporous silica-gel-immobilized Brønsted acid ionic liquid (SG@BAIL) nanocatalysts. In comparison to traditional heterogeneous catalysts, these immobilised heterogeneous catalysts have the advantage of ionic-liquid acidic sites and the advantage of solid silica gel as a support, increasing their catalytic activities. The catalysts were analysed using a series of physicochemical techniques and their catalytic efficiencies were evaluated during the acetalization of glycerol (G) with benzaldehyde (B). The influence of the counter-anions present in the SG@BAIL catalysts was initially investigated in terms of the percentage conversion vs. the reaction time at a particular temperature. Furthermore, different parametric studies relating to the acetalization reaction were carried out based on the catalyst with the maximum activity. SG-[C3ImC3SO3H][OTf] was observed to have the highest catalytic performance and durability during ecofriendly acetal synthesis, with the highest selectivity for 1,3-dioxane. Parametric studies of the acetalization reaction were carried out, and the catalyst showed noteworthy performance at 90 °C, showing 94% conversion in an equimolar reactant mixture under solvent-free conditions with 0.03 wt% catalyst loading in a short time span of 75 min. In addition, kinetics modelling was performed using reversible second-order kinetics to calculate the forward rate constants at various temperatures. The activation energy of the reaction was determined using the Arrhenius equation, and the overall activation energy was 69.33 kJ mol−1. These investigations have demonstrated the excellent potential of SG@BAIL catalysts for practical application in the glycerol acetalization process. [ABSTRACT FROM AUTHOR]

Our previous study on the photochemical CO2 reduction into CO catalyzed by the diazapyridinophane complexes of Fe, Co, and Ni revealed that (i) the Co catalyst shows the highest TOF but degrades rapidly, (ii) the Fe catalyst exhibits a lower TOF relative to Co but shows higher robustness, giving a higher TON, and (iii) the Ni complex shows no activity (Sakaguchi et al., Chem. Commun., 2019, 55, 8552). Here we show our DFT results unveiling that the Fe and Co catalysts can utilize multiple sets of frontier MO associations at the CO2 binding by including one of the SOMOs in a high-spin d7 Fe(I) and d8 Co(I) center, respectively, giving an increased driving force for these oxidative addition steps. Remarkably, two-electron reduction of CO2 to CO22− at the binding step is driven by the two electrons transferred from different d-based orbitals. The CoI species binds CO2 at the rate-limiting step with an activation barrier of 15.0 kcal mol−1, rationalizing the high initial TOF observed. However, the CoI(CO) species is given as a dead-end product, consistent with its relatively rapid deactivation. The Fe catalyst possesses a slightly higher barrier in CO2 binding (ΔG‡ = 15.8 kcal mol−1) but does not stabilize the FeI(CO) species which readily releases CO (ΔG = 3.5 kcal mol−1). The Ni catalyst has the smallest barrier in CO2 binding (ΔG‡ = 11.5 kcal mol−1) but the CO release is largely prohibited by the dead-end NiI(CO) species, consistent with its inactive character towards CO2 reduction. The combined results all satisfactorily explain the observed catalytic behaviors. [ABSTRACT FROM AUTHOR]

A synergistic combination of photoredox and polarity reversal catalysis enabled a hydrogen evolution cross-coupling of silanes with H2O, alcohols, phenols, and silanols, which afforded the corresponding silanols, monosilyl ethers, and disilyl ethers, respectively, in moderate to excellent yields. The dehydrogenative cross-coupling of Si–H and O–H proceeded smoothly with broad substrate scope and good functional group compatibility in the presence of only an organophotocatalyst 4-CzIPN and a thiol HAT catalyst, without the requirement of any metals, external oxidants and proton reductants, which is distinct from the previously reported photocatalytic hydrogen evolution cross-coupling reactions where a proton reduction cocatalyst such as a cobalt complex is generally required. Mechanistically, a silyl cation intermediate is generated to facilitate the cross-coupling reaction, which therefore represents an unprecedented approach for the generation of silyl cation via visible-light photoredox catalysis. [ABSTRACT FROM AUTHOR]

Selective oxidation of thioethers is an important reaction to obtain sulfoxides as synthetic intermediates for applications in the chemical industry, medicinal chemistry and biology or the destruction of warfare agents. The reduced Magneli-type tungsten oxide WO3−x possesses a unique oxidase-like activity which facilitates the oxidation of thioethers to the corresponding sulfoxides. More than 90% of the model system methylphenylsulfide could be converted to the sulfoxide with a selectivity of 98% at room temperature within 30 minutes, whereas oxidation to the corresponding sulfone was on a time scale of days. The concentration of the catalyst had a significant impact on the reaction rate. Reasonable catalytic effects were also observed for the selective oxidation of various organic sulfides with different substituents. The WO3−x nanocatalysts could be recycled at least 5 times without decrease in activity. We propose a metal oxide-catalyzed route based on the clean oxidant hydrogen peroxide. Compared to other molecular or enzyme catalysts the WO3−x system is a more robust redox-nanocatalyst, which is not susceptible to decomposition or denaturation under standard conditions. The unique oxidase-like activity of WO3−x can be used for a wide range of applications in synthetic, environmental or medicinal chemistry. [ABSTRACT FROM AUTHOR]

Recently, cost-effective production of high value-added furan chemicals from abundant and renewable bioresources has attracted much attention via a chemoenzymatic approach in an environmentally friendly reaction system. In this work, a chemoenzymatic cascade reaction for bridging tandem chemocatalysis and biocatalysis was constructed to valorize biomass into furfurylamine in a deep eutectic solvent (DES)–water system. Waste shrimp shell (SS) was used as a biobased carrier to prepare sulfonated tin-based solid acid (Sn-SS) for catalyzing sugarcane bagasse (SB) into furfural in DES–water. The prepared Sn-SS was characterized by XRD, SEM, FTIR spectroscopy and BET. Furfural (113.2 mM) was obtained in 62.3% yield from xylan in SB by Sn-SS (0.6 wt% dose) within 20 min at 170 °C in [ChCl][EG]–water (20 : 80, v : v). A potential catalytic mechanism was proposed for catalyzing SB into FAL and derivatives in [ChCl][EG]–water. Sequentially, one newly constructed recombinant Escherichia coli PRSFDuet-CV-AlaDH cells containing ω-transaminase and L -alanine dehydrogenase were used for the biological transamination of SB-derived furfural to furfurylamine in the presence of amine donor NH4Cl (2.0 mol NH4Cl/mol furfural) and cosubstrate glucose (1.0 mol glucose/mol furfural) at 35 °C and pH 8.0 without the removal of Sn-SS and residual SB. Within 1 h, SB-derived furfural was wholly aminated to furfurylamine with a productivity of 0.458 g furfurylamine per g xylan in SB by whole cells using NH4Cl as an amine donor in [ChCl][EG]–water (20 : 80, v : v). It was found that [ChCl][EG]–water enhanced furfural and furfurylamine yields. Compared to the aqueous system, this green [ChCl][EG]–water (20 : 80, v : v) system enabled the highly efficient production of furfurylamine from SB via chemoenzymatic cascade catalysis with a sulfonated Sn-SS catalyst and ω-transaminase biocatalyst by enhancing the catalytic activity and thermostability of chemocatalysts and biocatalysts. This chemoenzymatic cascade reaction strategy had potential application for utilizing renewable biomass into furan-based chemicals in the benign DES–water system. [ABSTRACT FROM AUTHOR]

Tungstate catalysts are well established for olefin epoxidation reactions, while their catalytic activity for CO2 insertion in epoxides is a more recent discovery. This dual reactivity of tungstate prompted the present development of a catalytic tandem process for the direct conversion of olefins into the corresponding cyclic organic carbonates (COCs). Each of the two steps was studied in the presence of the ammonium tungstate ionic liquid catalyst – [N8,8,8,1]2[WO4] – obtained via a benign procedure starting from ammonium methylcarbonate ionic liquids. The catalytic epoxidation first step was optimised on 1-decene as model substrate, using H2O2 as benign oxidant, [N8,8,8,1]2[WO4] as catalyst and phosphoric acid as promoter affording quantitative conversion with 92% selectivity towards decene oxide. Unfortunately, the addition of CO2 from the start (auto-tandem catalysis) gave low yields of decene carbonate (<10%). On the contrary, the addition of 1 atm CO2 and tetrabutyl ammonium iodide after completion of the epoxidation first step without any intermediate work-up (assisted-tandem catalysis) afforded a 94% yield in decene carbonate. The protocol could be scaled up to a 10 gram scale. The scope of the reaction was demonstrated for primary aliphatic olefins with different alkyl chain lengths (C6–C16), while cyclic and aromatic activated olefins such as cyclohexene and styrene suffered from the formation of undesired overoxidation products in the first step. [ABSTRACT FROM AUTHOR]

Herein we report an experimental and computational study of a family of four coordinated 14-electron complexes of Rh(III) devoid of agostic interactions. The complexes [X–Rh(κ3(P,Si,Si)PhP(o-C6H4CH2SiiPr2)2], where X = Cl (Rh-1), Br (Rh-2), I (Rh-3), OTf (Rh-4), Cl·GaCl3 (Rh-5); derive from a bis(silyl)-o-tolylphosphine with isopropyl substituents on the Si atoms. All five complexes display a sawhorse geometry around Rh and exhibit similar spectroscopic and structural properties. The catalytic activity of these complexes and [Cl–Ir(κ3(P,Si,Si)PhP(o-C6H4CH2SiiPr2)2], Ir-1, in styrene and aliphatic alkene functionalizations with hydrosilanes is disclosed. We show that Rh-1 catalyzes effectively the dehydrogenative silylation of styrene with Et3SiH in toluene while it leads to hydrosilylation products in acetonitrile. Rh-1 is an excellent catalyst in the sequential isomerization/hydrosilylation of terminal and remote aliphatic alkenes with Et3SiH including hexene isomers, leading efficiently and selectively to the terminal anti-Markonikov hydrosilylation product in all cases. With aliphatic alkenes, no hydrogenation products are observed. Conversely, catalysis of the same hexene isomers by Ir-1 renders allyl silanes, the tandem isomerization/dehydrogenative silylation products. A mechanistic proposal is made to explain the catalysis with these M(III) complexes. [ABSTRACT FROM AUTHOR]

Umbrella-sampling density functional theory molecular dynamics (DFT-MD) has been employed to study the full catalytic cycle of the allylic oxidation of cyclohexene using a Cu(II) 7-amino-6-((2-hydroxybenzylidene)amino)quinoxalin-2-ol complex in acetonitrile to create cyclohexenone and H2O as products. After the initial H-atom abstraction step, two different reaction pathways have been identified that are distinguished by the participation of alkyl hydroperoxide (referred to as the "open" cycle) versus the methanol side-product (referred to as the "closed" cycle) within the catalyst recovery process. Importantly, both pathways involve dehydrogenation and re-hydrogenation of the –NH2 group bound to the Cu-site – a feature that is revealed from the ensemble sampling of configurations of the reactive species that are stabilized within the explicit solvent environment of the simulation. Estimation of the energy span from the experimental turnover frequency yields an approximate value of 22.7 kcal mol−1 at 350 K. Whereas the closed cycle value is predicted to be 26.2 kcal mol−1, the open cycle value at 16.5 kcal mol−1. Both pathways are further consistent with the equilibrium between Cu(II) and Cu(III) that has previously been observed. In comparison to prior static DFT calculations, the ensemble of both solute and solvent configurations has helped to reveal a breadth of processes that underpin the full catalytic cycle yielding a more comprehensive understanding of the importance of radical reactions and catalysis recovery. [ABSTRACT FROM AUTHOR]

In this study, an efficient catalytic system composed of deep eutectic solvents (DESs) was developed by adjusting the basicity of hydrogen bond donors (HBDs) to synthesize poly(isosorbide) carbonate (PIC) with high weight average molecular weight (Mw). It was demonstrated that the Mw of PIC prepared by using nearly neutral [EminOH]Cl–2EG was the highest. The results of the transesterification kinetics with different catalysts supported that the transesterification rate was significantly promoted as the basicity of DESs increased but their strong alkalinity inhibited the Mw of PIC. Therefore, the degradation of PIC was investigated to reveal the mechanism of the influence of basicity on the molecular weight of PIC. The strong alkalinity of DESs would cause the depolymerization of the macromolecular chains and ultimately limit the molecular weight of the product, proving the experimental fact that a near-neutral catalyst was more conducive to the Mw of PIC. Finally, a reasonable mechanism of synergistic catalysis was proposed based on 1H NMR spectroscopy, Fourier transform infrared spectroscopy (FT-IR) and experimental results. The metal-free, low-cost, high catalytic activity DES catalyst involved here is a practical candidate for advanced bio-based polycarbonate. [ABSTRACT FROM AUTHOR]

Herein, we report an intramolecular radical cyclization reaction towards the synthesis of pyrrolidinone derivatives via metal-free photoredox catalysis under irradiation from blue LEDs. Some of the remarkable features of this protocol include synthetic efficiency, green reaction profile, easy isolation of products and short reaction time. The photophysical properties of synthesized compounds were investigated via steady state and time-resolved fluorescence spectroscopy in the solid state. Results showed the promising opportunity for their spectral tuning together with large Stokes-shifted and highly active fluorescence emission, thus indicating that these molecular scaffolds can be effective probes for the biological applications and development of opto-electronic devices. [ABSTRACT FROM AUTHOR]

Palladium-catalyzed coupling of 4,5-dibromo-2,7,9,9-tetramethylacridan with two equivalents of 1,3-diisopropylimidazolin-2-imine afforded 4,5-bis(1,3-diisopropylimidazolin-2-imino)-2,7,9,9-tetramethylacridan, H[AII2]. Reaction of the H[AII2] pro-ligand with one equivalent of [M(CH2SiMe3)3(THF)2] (M = Y or Sc) yielded the base-free neutral dialkyl complexes [(AII2)M(CH2SiMe3)2] {M = Y (1) and Sc (2)}. The rigid AII2 pincer ligand affords a similar steric profile to the previously reported XA2 pincer ligand, but is monoanionic rather than dianionic. Reaction of 1 with one equiv. of [CPh3][B(C6F5)4] in C6D5Br generated a highly active catalyst for intramolecular alkene hydroamination. However, rather than forming the expected monoalkyl cation, this reaction afforded a diamagnetic product which was identified as [(AII2-CH2SiMe3)Y(CH2SiMe3)2][B(C6F5)4] (3; AII2-CH2SiMe3 is a neutral tridentate ligand with a central amine donor flanked by imidazolin-2-imine groups) in approx. 20% yield, accompanied by HCPh3 (∼2 equiv. relative to 3), an unidentified paramagnetic product (detected by EPR spectroscopy), and a small amount of colourless precipitate. The unexpected reactivity of 1 with CPh3+ is thought to involve initial AII2 ligand backbone oxidation, given that the zwitterionic form of the ligand contains a phenylene ring with two adjacent anionic nitrogen donors, similar to a redox-non-innocent, dianionic ortho-phenylenediamido ligand. [ABSTRACT FROM AUTHOR]

The catalytic conversion of CO or CO/CO2 mixtures to higher alcohols (HAs) using hydrogenation reactions remains challenging in C1 chemistry and also one of the most promising reactions for the utilization of non-petroleum resources. Here, the experiment and characterization tests of CuCoMn/Al2O3 show that copper is much more dispersed on γ-Al2O3 than cobalt, and the interaction between cobalt and Mn metals is stronger. And, mixed cobalt–manganese oxides are formed in the calcined catalyst, promoting the formation of higher alcohols. Under the optimum conditions, the catalyst demonstrated a total alcohol selectivity of 44.6%, and the fraction of higher alcohols reached up to 85.3% among the total alcohol products, which is superior to the classical modified CuCo-based catalysts. And in the gas mixture reaction with a CO : CO2 ratio of 8 : 2, the conversion rate of the catalyst to CO and CO2 reached 34.8% and 27.3%, respectively, and the selectivity (C1+ slate 1-alcohol) was 53.2%. [ABSTRACT FROM AUTHOR]

To deeply understand the role of P in hydrodeoxygenation (HDO), SiO2-supported Ni and Ni–P catalysts with different P/Ni ratios (x) were prepared. The as-prepared samples were characterized by various characterization methods. The HDO activity and product distribution over the Ni/SiO2 and N–P/SiO2-x were compared and the effects of x on the structure, acidity, formation mechanism of active phases and HDO performance were studied taking m-cresol HDO as a model reaction. The results showed that the introduction of P promotes the formation of smaller active sites and contributes to the creation of weak and medium strength acid sites through the formation of P–OH groups and Niδ+ in Ni2P. HDO over the Ni/SiO2 catalyst occurs mainly via the hydrogenation (HYD) route with 3-methyl-cyclohexanol (3-MCHnol) as the main product. However, for Ni–P/SiO2-x catalysts, methyl-cyclohexane (MCH) selectivity increases first and then decreases with the increase of x, reaching a maximum of 95% at x = 1. The acidity generated by the introduction of P contributes to increased MCH selectivity, while the dehydration of 3-MCHnol to MCH occurs mainly on acid sites. However, the excessively high P content (x ≥ 2.0) leads to a significant increase of MB (toluene) selectivity, which is associated with the increase in Ni(I) sites. About 100% m-cresol conversion was achieved with Ni–P/SiO2-1.0 when the m-cresol (g)/catalyst (g) ratio was 3, with MCH (99.4%) as the major product, showing great promise for deep HDO catalysis. [ABSTRACT FROM AUTHOR]

Hybrid materials of metal–organic frameworks (MOFs) and nanoparticles (NPs) have attracted significant attention because of the wide variety of attractive properties derived from the two components. In the last decade, the development of synthesis techniques for NP/MOF composites was particularly significant. In the field of catalysis in particular, various synergistic effects that make the composites attractive catalysts have been reported. However, the role of MOFs in the composite catalysts is still not well understood and is being elucidated. In this feature article, we focus on recent progress in NP/MOF composite catalysts, concentrating on the analysis of the interaction between NPs and MOFs and the reaction mechanisms, together with the synthetic techniques used for NP/MOF hybrid materials. [ABSTRACT FROM AUTHOR]

Three 3-component copper(I)-based slider-on-deck systems served as catalysts for a click reaction showing a higher catalytic activity with increasing sliding speed. Upon addition of brake stones, the motion of the resulting 4-component machinery was slowed and eventually stopped (on the NMR time scale) with the effect that catalysis was reduced or obstructed. [ABSTRACT FROM AUTHOR]

In the last few decades, worldwide scientists have been motivated by the promising production of chemicals from the widely existing methane (CH4) under mild conditions for both chemical synthesis with low energy consumption and climate remediation. To achieve this goal, a whole library of catalytic chemistries of transforming CH4 to various products under mild conditions is required to be developed. Worldwide scientists have made significant efforts to reach this goal. These significant efforts have demonstrated the feasibility of oxidation of CH4 to value-added intermediate compounds including but not limited to CH3OH, HCHO, HCOOH, and CH3COOH under mild conditions. The fundamental understanding of these chemical and catalytic transformations of CH4 under mild conditions have been achieved to some extent, although currently neither a catalyst nor a catalytic process can be used for chemical production under mild conditions at a large scale. In the academic community, over ten different reactions have been developed for converting CH4 to different types of oxygenates under mild conditions in terms of a relatively low activation or catalysis temperature. However, there is still a lack of a molecular-level understanding of the activation and catalysis processes performed in extremely complex reaction environments under mild conditions. This article reviewed the fundamental understanding of these activation and catalysis achieved so far. Different oxidative activations of CH4 or catalytic transformations toward chemical production under mild conditions were reviewed in parallel, by which the trend of developing catalysts for a specific reaction was identified and insights into the design of these catalysts were gained. As a whole, this review focused on discussing profound insights gained through endeavors of scientists in this field. It aimed to present a relatively complete picture for the activation and catalytic transformations of CH4 to chemicals under mild conditions. Finally, suggestions of potential explorations for the production of chemicals from CH4 under mild conditions were made. The facing challenges to achieve high yield of ideal products were highlighted and possible solutions to tackle them were briefly proposed. [ABSTRACT FROM AUTHOR]

The development of visible-light-induced photoacid catalyzed glycosylation is reported. The eosin Y and PhSSPh catalyst system is applied to realize glycosylation with different glycosyl donors upon light irradiation. The reaction shows a broad substrate scope, including both glycosyl donors and acceptors, and highlights the mild nature of the reaction conditions. [ABSTRACT FROM AUTHOR]

A novel, efficient and facile protocol for the synthesis of a series of [Ru(NHC)(CO3)(p-cymene)] complexes is reported. This family of Ru-NHC complexes was obtained from imidazol(in)ium tetrafluoroborate or imidazolium hydrogen carbonate salts in moderate to excellent yields, employing sustainable weak base. The ruthenium complexes were successfully utilized in the transfer hydrogenation of ketones as highly active multifunctional catalysts. [ABSTRACT FROM AUTHOR]

Considering the irreplaceable importance of photocatalytic functionalization reactions and the widespread attention paid to the use of metal–organic frameworks, especially their modified variants, for this purpose in recent years, different types of HKUST-1/POMoW composites were prepared through the immobilization of a series of Keggin-type polyoxometalates (POMs; POW = H3PW12O40, POMo = H3PMo12O40, and POMoW = H3PMo6W6O40) on HKUST-1 as a metal–organic framework (HKUST-1; Cu3(1,3,5-benzenetricarboxilicacid)2). Then, to produce HKUST-1/Cs-POM, the substitution of H+ cations with Cs+ ones as counter cations was carried out. The prepared composites were fully characterized with the PXRD (powder X-ray diffraction), FT-IR (Fourier transform infrared spectroscopy), BET and BJH (sorption of N2), TGA (thermo-gravimetric analysis), SEM (scanning electron microscopy), EDX (energy dispersive X-ray), TEM (transmission electron microscopy), UV-vis DRS (diffuse reflectance UV-vis spectroscopy), photoluminescence (PL) spectroscopy and ICP-AES (inductively coupled plasma atomic emission spectroscopy) techniques. The great importance of the amide functional group and the attractiveness of photocatalytic oxidative functionalization reactions led us to study the formation of this functional group using the prepared catalytic system in line with our previous research in this field. The HKUST-1/Cs-POMoW composite showed a raised photocatalytic performance compared to the discrete components, HKUST-1 and Cs-POMs, in aerobic oxidative amidation of alcohols under illumination with visible light, owing to the presence of catalytically active Cs-POMs deposited on the MOF particles. Besides, the combination of composite components mitigated the recombination rate of the electron–hole pairs, raising its photocatalytic activity. The attractiveness of fluorine solvents for oxidation reactions has led to the study of their role in the efficiency of oxidative amidation of alcohols and their significant effect on the efficiency of the process has been confirmed. The Cu-MOF/POM catalyst showed excellent stability during the reaction, and no significant decrease in its ability was observed during five consecutive cycles. [ABSTRACT FROM AUTHOR]