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The well‐known Corey–Bakshi–Shibata (CBS) reduction is a powerful method for the asymmetric synthesis of alcohols from prochiral ketones, often featuring high yields and excellent selectivities. While steric repulsion has been regarded as the key director of the observed high enantioselectivity for many years, we show that London dispersion (LD) interactions are at least as important for enantiodiscrimination. We exemplify this through a combination of detailed computational and experimental studies for a series of modified CBS catalysts equipped with dispersion energy donors (DEDs) in the catalysts and the substrates. Our results demonstrate that attractive LD interactions between the catalyst and the substrate, rather than steric repulsion, determine the selectivity. As a key outcome of our study, we were able to improve the catalyst design for some challenging CBS reductions., London dispersion (LD) interactions facilitate the enantioselectivity in the Corey–Bakshi–Shibata (CBS) reduction. Employing a combination of computational and experimental studies, we provide a modern view on the origin of enantioselectivity in this powerful organocatalyzed reaction. The results demonstrate that attractive LD interactions between the catalyst and the substrate rather than steric repulsion determine the selectivity.

In this study, cyclohexene was used as a representative of olefin and catalyzed by CeY zeolites in a fixed-bed reactor under mild conditions, and the influence of Ce species in hydride transfer reaction over CeY zeolites was evaluated. CeY zeolites show more excellent hydride transfer properties than HY zeolite. Based on the results of almost identical Bronsted acid properties but not the product distributions for 0.075CeY and 0.075CeY(DC) samples, it should be suggested that the Bronsted acid strength and density are not the deciding factors to the hydride transfer reaction. A unique band at 1442 cm−1 in situ FTIR spectroscopy spectra are assigned to pyridine complexes bonded to a class of active Ce species that could reversibly migrate from the core of SOD cages to its 6-rings mouth towards the supercages. These results provide valuable information that these active Ce species should play a synergistic role with the Bronsted acid sites in enhancing the hydride transfer reaction with a bimolecular mechanism over CeY zeolites.

While 1,2-addition represents the most common mode of alkyne hydroboration, herein we describe a new 1,1-hydroboration mode. It is the first demonstration of gem-(H,B) addition to an alkyne triple ...

Main-group-element compounds with energetically high-lying donor and low-lying acceptor orbitals are able to mimic chemical bonding motifs and reactivity patterns known in transition metal chemistry, including small-molecule activation and catalytic reactions. Monovalent group 13 compounds and divalent group 14 compounds, particularly silylenes, have been shown to be excellent candidates for this purpose. However, one of the most common reactions of transition metal complexes, the direct reaction with carbon monoxide and formation of room-temperature isolable carbonyl complexes, is virtually unknown in main-group-element chemistry. Here, we show the synthesis, single-crystal X-ray structure, and density functional theory computations of a room-temperature-stable silylene carbonyl complex [L(Br)Ga]2Si:–CO (L = HC[C(Me)N(2,6-iPr2-C6H3)]2), which was obtained by direct carbonylation of the electron-rich silylene intermediate [L(Br)Ga]2Si:. Furthermore, [L(Br)Ga]2Si:–CO reacts with H2 and PBr3 with bond activation, whereas the reaction with cyclohexyl isocyanide proceeds with CO substitution. Compounds of main-group elements rarely undergo direct carbonylation reactions. Now, an electron-rich silylene intermediate has been shown to readily react with CO to form a silylene carbonyl complex that is stable at room temperature. This complex engages in CO substitution as well as oxidative addition reactions.

A series of CeY zeolites with different cerium loadings and calcined at different temperatures were prepared and used as the adsorbent for the desulfurization of thiophene containing model oil. The CeY zeolites were characterized by XRD, N2 sorption, FT-IR spectroscopy and GC-SCD and GC-MSD techniques. The effects of aromatics and olefins on the adsorption desulfurization performance were investigated and the active species and reaction mechanism for the adsorption desulfurization on CeY zeolites were probed. The results indicate that the CeY zeolite calcined at 150°C is provided with a large number of Bronsted acid sites and hydroxylated cerium species in the supercages, which can synergistically promote the thiophene oligomerization and then enhance the sulfur breakthrough adsorption capacity (18.45 mg(S)/g). However, a further increase in the calcination temperature and cerium loading may greatly reduce the number of active sites for the adsorption desulfurization and suppress the thiophene oligomerization reaction, leading to a significant decrease in the sulfur breakthrough adsorption capacity (4.03 mg(S)/g). For the thiophene model oils containing low concentration of 1-hexene (

Adsorption desulfurization performance of NaY, HY and CeHY zeolites is evaluated in a miniature fixed-bed flow by model gasoline containing with thiophene, tetrahydrothiophene, 2-methylthiophene, benzothiophene or mixed sulfur compounds. The structural properties of adsorbents are characterized by XRD, N2-adsorption and XPS techniques. Adsorption desulfurization mechanisms of these sulfur compounds over the specific active sites of adsorbents as a major focus of this work, have been systematically investigated by using in situ FT-IR spectroscopy with single and double probing molecules. Desulfurization experimental results show that the CeHY adsorbent exhibits superior adsorption sulfur capacity at breakthrough point of zero sulfur for ultra-deep removal of each thiophenic sulfur compound, especially in the capture of aromatic 2-methylthiophene (about ca. 28.6 mgS/gadsorbent). The results of in situ FT-IR with single probing molecule demonstrate an important finding that high oligomerization ability of thiophene or 2-methylthiophene on the CeHY can promote the breakthrough adsorption sulfur capacity, mainly resulting from the synergy between Bronsted acid sites and Ce(III) hydroxylated species active sites located in the supercages of CeHY. Meanwhile, the result of in situ FT-IR with double probing molecules further reveals the essence of oligomerization reactions of thiophene and 2-methylthiophene molecules on those specific active sites. By contrast, the oligomerization reaction of benzothiophene molecules on the active sites of CeHY cannot occur due to the restriction of cavity size of supercages, but they can be adsorbed on the Bronsted acid sites via protonation, and on Ce(III) hydroxylated species and extra-framework aluminum hydroxyls species via direct “S-M” bonding interaction. As to the tetrahydrothiophene, adsorption mechanism is similar to that of benzothiophene, except in the absence of protonation. The paper can provide a new design idea of specific adsorption active sites in excellent desulfurization adsorbents for elevating higher quality of FCC gasoline in the future.

Semihydrogenation of alkynes to alkenes represents a fundamentally useful transformation. In addition to the well-known cis- and trans-semihydrogenation, herein a geminal semihydrogenation of internal alkynes featuring 1,2-migration is described, which provides new access to the useful terminal vinylsilanes. This process also presents a new mode of reactivity of silyl alkynes. With the proper choice of the cationic [CpRu(MeCN)3]PF6 catalyst and a suitable silyl group, both aryl- and alkyl-substituted silyl alkynes can participate in this highly efficient gem-selective process. Furthermore, dedicated condition optimization also allowed switching of selectivity from gem to trans by using a combination of parameters, including the suitable silyl group, additive, and H2 pressure. A systematic DFT study on the reaction mechanism revealed that the formation of the gem-H2 Ru-carbene might be the key intermediate in both gem- and trans-addition reactions, rather than the Ru-vinylidene intermediate. The DFT results were further supported by carefully designed control experiments. This uncommon gem-addition combined with 1,2-silyl migration in the metal-carbene intermediate should open up a new synthetic avenue for alkyne transformations.

Reactions of two equivalents of LGa {L = HC[C(Me)NAr]2; Ar = 2,6‐iPr2‐C6H3} with SbX3 (X = Cl, Br) yield double‐inserted products (LGaX)2SbX (X = Cl 1, Br 2), which were isolated at –40 °C. Warming solutions of 1 and 2 to ambient temperature results in intramolecular elimination of LGaX2 and formation of Ga‐substituted stibinidenes L(X)GaSb as reaction intermediates, which were stabilized by coordination of strong σ‐donating carbenes. Four carbene‐stabilized stibinidenes MeCAAC‐SbGa(X)L {MeCAAC = [H2C(CMe2)2NAr]C, Ar = 2,6‐iPr2‐C6H3, X = Cl 3, Br 4} and IDipp‐SbGa(X)L {IDipp = 1,3‐bis(2,6‐diisopropylphenyl)‐imidazol‐2‐ylidene, X = Cl 5, Br 6} were characterized by single‐crystal X‐ray diffraction and the nature of the bonding in 3–6 was further investigated by quantum chemical methods. The studies reveal substantial Sb–Ccarbene π‐backbonding contributions in 3 and 4, whereas the IDipp‐stabilized derivatives 5 and 6 exhibit Sb–Ccarbene single bonds. DFT computations with and without dispersion corrections reveal that dispersion interactions mainly from the bulky aryl groups decisively contribute to the stability of 3–6. Dedicated to Prof. E. Niecke on the occasion of his 80th birthday.

The formation of S–S bonds has great significance and value in synthetic chemistry and bioscience. To pursue a sustainable approach for such a synthesis, an aerobic oxidative coupling method for the efficient preparation of organic disulfanes, using a low-toxic natural gallic acid as an organocatalyst, inexpensive MnCO3 as a cocatalyst, O2 as the terminal oxidant and water as the solvent, has been successfully developed. Such metal–organic cooperative catalytic protocol provided an access to various symmetrical and unsymmetrical disulfanes in up to 99% yield. Gram scale synthesis with practical convenience and low loading of catalysts further illustrates the practicability of our method.

Low molecular weight gelators (LMWG) have been extensively explored in many research fields due to their unique reversible gel-sol transformation. Intermolecular interactions between LMWG are known as the main driving force for self-assembly. During this self-assembly process, individually analyzing the contribution difference between various intermolecular interactions is crucial to understand the gel properties. Herein, we report 2,5-bis(hexadecylcarbamoyl)terephthalic acid (BHTA) as a LMWG, which could efficiently form a stable organogel with n-hexadecane, diesel, liquid paraffin, and base lubricant oil at a relatively low concentration. To investigate the contribution difference of intermolecular interactions, we first finished FT-IR spectroscopy and XRD experiments. On the basis of the d-spacing, a crude simulation model was built and then subjected to molecular dynamics (MD) simulations. Then, we knocked out the energy contribution of the H-bonding interactions and π-π stacking, respectively, to evaluate the intermolecular interactions significantly influencing the stability of the gel system. MD simulations results suggest that the self-assembly of the aggregates was mainly driven by dense H-bonding interactions between carbonyl acid and amide moieties of BHTA, which is consistent with FT-IR data. Moreover, wave function analysis at a quantum level suggested these electrostatic interactions located in the middle of the BHTA molecule were surrounded by strong dispersion attraction originating from a hydrophobic environment. Furthermore, we also confirmed that 2 wt % BHTA was able to form gel lubricant with 150BS. The coefficient of friction (COF) data show that the gel lubricant has a better tribological performance than 150BS base lubricant oil. Finally, XPS was performed and offered valuable information about the lubrication mechanism during the friction.

We report the synthesis and structural characterization of Ga-substituted diarsene [L(EtO)GaAs]2, which is an exemplary case of a Ga-substituted dipnictene of the general type [L(X)Ga]2E2 (L = C[C(Me)N(2,6-i-Pr2-C6H3)]2, X = F, Cl, Br, I, NMe2, OEt; E = As, Sb, Bi). We examined this extended series of compounds computationally and found that attractive London dispersion interactions between the substituents on the N,N′-chelating β-diketiminate ligands as well as pnictogen−π interactions between the group 15 metal center and the ligand are key factors for the stability and the electronic structures of such types of complexes.

Electronic skin (e-skin) with skin-like flexibility and tactile sensation will promote the great advancements in the fields of wearable equipment. Thus, the multifunction and high robustness are two important requirements for sensing capability of the e-skin. Here, a fully organic self-powered e-skin (FOSE-skin) based on the triboelectric nanogenerator (TENG) is developed. FOSE-skin based on TENG can be fully self-healed within 10 hours after being sheared by employing the self-healing polymer as a triboelectric layer and ionic liquid with the temperature sensitivity as an electrode. FOSE-skin based on TENG has the multifunctional and highly robust sensing capability and can sense the pressure and temperature simultaneously. The sensing capability of the FOSE-skin based on TENG can be highly robust with no changes after self-healing. FOSE-skin based on TENG can be employed to detect the arm swing, the temperature change of flowing water, and the motion trajectory. This work provides a new idea for solving the issues of monofunctional and low robust sensing capability for FOSE-skin based on TENG, which can further promote the application of wearable electronics in soft robotics and bionic prosthetics.

The electrochemical behaviors of three half-sandwich iron(II) complexes, [CpFe(CO) 2 X] (Cp = cyclopentadienyl, 1 : X = Cl; 2 : X = Br; 3 : X = I) were investigated. For the three complexes, two reduction processes at ca . −1.3 V and −2.0 V were observed. They are assigned to the reductions of Fe(II) → Fe(I) couple and the reduction of the dimer, [CpFe (μ-CO)(CO)] 2 ( Fp 2 ), which formed via the dimerization of the neutral intermediate “CpFe(CO) 2 ” ( Fp ) generated from the first reduction, respectively. Our results ruled out the possibility of two-electron reduction for the first process. Using stop-flow infrared spectroscopic technique (SFIS) allowed us to trace the rapid chemical reactions and the first-order reaction rate constants for the formations of both Fp and Fp 2 were derived as 0.27 and 0.43 s −1 , respectively. Both complexes 1 and Fp 2 could be reduced by LiHBEt 3 . In the reduction, ligand exchange reaction occurred between the chloride and hydride, which was evidenced by the observation the absorption bands of [CpFe(CO) 2 H] ( FpH ). Their reduction reactions abided first-order model for the complex and the reducing agent. By assuming that equal moles of the complex and the reducing agent were used in the reduction, a rate equation was established. Again, the SFIS technique was employed to follow the reductions and linear plots were observed to give the rate constants as 14 and 18 mol −1 L s −1 , respectively. The catalysis on proton reduction of the complexes was also examined. Sufficient experimental evidences in our work and the analysis of literature data suggested strongly that the catalytic species was not the neutral species Fp . Instead the anion, FpX − , was responsible for the catalysis. The poor performance in catalysis of these complexes resulted from the competing reaction coupled to the first reduction, loss of the halide upon reduction. The resultant neutral species, Fp dimerized rapidly into Fp 2 .

Carbocations can be categorized into classical carbenium ions and non-classical carbonium ions. These intermediates are ubiquitous in reactions of both fundamental and practical relevance, finding application in the petroleum industry as well as the discovery of new drugs and materials. Conveying stereochemical information to carbocations is therefore of interest to a range of chemical fields. While previous studies targeted systems proceeding through classical ions, enantiocontrol over their non-classical counterparts has remained unprecedented. Here we show that strong and confined chiral acids catalyse enantioselective reactions via the non-classical 2-norbornyl cation. This reactive intermediate is generated from structurally different precursors by leveraging the reactivity of various functional groups to ultimately deliver the same enantioenriched product. Our work demonstrates that tailored catalysts can act as suitable hosts for simple, non-functionalized carbocations via a network of non-covalent interactions. We anticipate that the methods described herein will provide catalytic accessibility to valuable carbocation systems. In 1949, Winstein and Trifan proposed that the 2-norbornyl cation adopts a bridged, non-classical structure. Now, the generation of an asymmetric environment around the three-centre two-electron bond of such an ion has been reported, enabling highly enantioselective catalytic addition reactions to a simple, non-functionalized non-classical cation.

The reaction of β-hydroxyethylation is essential to the current practice of organic chemistry. Here, we proposed a new and green route to synthesize 2-hydroxyethyl n-alkyl sulfide with n-alkyl mercaptan and ethylene carbonate (EC) in the presence of alkali carbonates as catalysts and revealed the mechanism by experiments and theoretical calculations. The reaction reported proceeds rapidly with high yields when it is performed at 120 °C and the catalytic loading is ∼1 mol%. This protocol is applicable to other mercaptans to synthesize the corresponding β-hydroxyethyl sulfide. Density functional theory-based calculations show the energy profile for the reaction pathway. The rate-determining step is the ring-opening of EC. A negatively charged O atom of alkali carbonates approaches the S atom of –SH under the influence of hydrogen bonds. An activated S atom that carries more negative charge serves as a nucleophilic reagent and assists in the ring-opening of EC by reducing the Mayer bond orders of the C1–O1 bond in EC. Alkali cations also contribute to the C1–O1 bond cleavage. The energy barrier for the ring-opening of EC decreases with the decrease of electronegativity of alkali cations. Subsequent transference of a H atom leads to the formation of β-hydroxyethyl sulfide, the dissociation of CO2 and the reduction of K2CO3.

A series of CuNaY zeolites with different Cu loadings were prepared from NaY by liquid-phase ion exchange (LPIE) method. The microstructure and textural properties of CuNaY zeolites were characterized by XRD and N2 sorption and their adsorption desulfurization performance were evaluated with a model oil containing thiophene by the dynamic adsorption method. Combined with the Py-FTIR and NH3-TPD methods, the amounts of surface acid sites and effective Cu+ species were determined quantitatively and a correlation between the effective adsorption sites and adsorption desulfurization performance of CuNaY zeolite towards thiophene was then established. The results revealed that the surface acidity and the active copper species in Y zeolite can be regulated effectively by controlling the copper loading; an adsorbent provided with abundant effective adsorption sites and excellent adsorption desulfurization performance can be obtained by loading appropriate amount of copper. On the contrary, an excessively high copper loading may promote the formation of polymeric copper species in the cavity of Y zeolite, which leads to a decrease in the number of effective adsorption sites as well as a decrease in the adsorption capacity of CuNaY zeolite towards thiophene.

H2O2 is produced industrially by the anthraquinone method, in which energy consumption is high because of its multistep hydrogenation and oxidation reactions. In this work, hollow copper-doped graphitic carbon nitride (g-C3N4) microspheres with outstanding photocatalytic H2O2 production ability are prepared. The characterization results demonstrate that Cu+ is not present as the oxide but instead inserts at the interstitial position through coordinative Cu(I)-N bonds. These Cu(I)-N active sites can act as chemical adsorption sites to activate molecular O2. Moreover, as an “electron transfer bridge”, Cu(I)-N active sites promote electron transfer from the catalyst to the adsorbed O2 molecules. The as-prepared copper-doped g-C3N4 displays much higher H2O2 equilibrium concentration and formation rate than neat g-C3N4 prepared by calcination does, as well as excellent structural stability. Density functional theory simulations show that Cu(I)-N active sites can adsorb the O2 molecules with high adsorption energy and elongate the O O bond. Charge density difference results confirm the electron transfer from the Cu+ doping sites to the O2 molecules. The Mulliken charge is −0.51 when the O2 adsorbed on Cu+ doping sites. This electron-rich environment is beneficial to the H+ attack to form H2O2.

Cage clusters are a discrete chemically and topologically diverse family of molecule-based functional materials. Presented here are two isostructural M48 (M = CoII for LSHU01, NiII for LSHU02) cage clusters with a merohedral icosahedral cage structure featuring 12 M4-TC4A (H4TC4A, p-tert-butylthiacalix[4]arene) second building units as vertices and 18 asymmetric 5-(1H-tetrazol-1-yl)isophthalate ligands as faces. They are the highest-nuclearity cage compounds of CoII and NiII. The activated Co48 cage exhibited high selectivity in the sorption of C3H8 over CH4 under ambient conditions. Frequency response experiments indicated that the extrinsic voids and matrix interface of the activated crystalline samples are primarily responsible for the observed gas adsorption performance.

Full reaction pathways for acetylene hydrogenation on model catalysts are important for understanding the influence of ethylene selectivity and the formation of carbonaceous species. Herein, we report detailed hydrogenation and dehydrogenation reaction pathways for acetylene on the Pd(100) surface and its surface alloys with Ag atoms using first principles calculations. All adsorption species with two C atoms were taken into account. Thirteen corresponding reaction barriers were compared to analyse the reaction activity and selectivity. The selectivity for ethylene of pure Pd(100) surface was not suitable owing to the low reaction barrier for converting CHCH2 species to CHCH3 species and the high reaction barrier for ethylene formation. When the surface Ag concentration was 50%, in which all surface Pd atoms were separated, the ethylene selectivity was enhanced owing to the raised reaction barrier for converting CHCH2 to CHCH3. By analysing the formation of carbonaceous species and their hydrogenation reactions, it was found that, when carbonaceous species were formed on the catalyst, they were difficult to convert back to acetylene and ethylene molecules when hydrogen was supplied. Therefore, the Pd–Ag(100) facet catalyst was not beneficial for the movement of carbon deposits, with the low selectivity mainly due to hydrogenation of the carbonaceous species rather than over-hydrogenation of ethylene. These results will significantly influence current understanding of morphology designations in Pd–Ag bimetallic nanocatalysts.

Pyrolysis of dichloroethane is an important reaction for the production of vinyl chloride monomer. The high operating temperature and low efficiency are, however, nuisances for this process. In this manuscript, a supported structure-controlled graphitic carbon nitride is reported as a highly efficient catalyst for dehydrochlorination of 1,2-dichloroethane (1,2-DCE). The results indicate that the “defects” of the active component, i.e., the chain terminations of the carbon nitride, which tend to form at low synthesis temperature of the catalyst, show high catalytic activities for the dehydrochlorination of 1,2-dichloroethane, while for the high degree of polymerization of carbon nitride, which tends to increase at high synthesis temperature, relatively low activities for the reaction can be found. These findings highlight the role of the “defects”, i.e., chain terminations, of the material in the reaction and also provide a strategy for the selective synthesis of highly active N-doped carbon catalysts for this reaction.

Photothermal therapy (PTT) has been extensively developed as an effective approach against cancer. In some cases, however, PTT can trigger inflammatory responses, in turn simulating tumor regeneration and hindering subsequent therapy. We herein developed a therapeutic strategy able to deliver enhanced PTT and simultaneously inhibite PTT-induced inflammatory response. 1-Pyrene methanol was utilize to synthesize anti-inflammatory prodrug pyrene-aspirin (P-aspirin) with cleavable ester bond, and also facilitate loading the prodrug on gold nanorod (AuNR)-encapsulated graphitic nanocapsule (AuNR@G), a photothermal agent, through π-π interaction. Such AuNR@G-P-aspirin complexes were used for near-infrared laser-triggered photothermal ablation of solid tumor and simultaneous inhibition of PTT-induced inflammation through the release of aspirin in tumor milieu. This strategy showed excellent effects in vitro and in vivo, thus having profound significance for the extended development of PTT.

CeY samples with different cerium (Ce) ions initial distribution were prepared by diverse preparation processes. The correlative influence of Ce ions distribution on the intracrystalline structure and catalytic mechanism of Y-type zeolite was studied by X-ray diffraction (XRD), Rietveld refinement, X-ray fluorescence spectrometry (XRF), energy-dispersive X-ray spectroscopy (EDS), infrared (IR) spectra, NH3 temperature-programmed desorption (NH3-TPD), N2 physical adsorption-desorption and micro-activity test (MAT). The results indicated that Ce ions were concentrated on the surface (supercage) of CeY zeolite would reduce the number of acid sites and the ratio of Bronsted acid and Lewis acid (B/L). Once Ce ions concentrated in the sodalite cage, it would participate in the coordination with framework oxygen atoms under the condition of steric hindrance. Meanwhile, Ce ions would preferentially promote the B/L value of weak acid by retaining more intracrystalline framework Al atoms in sodalite cage, which was beneficial to the conversion of heavy oil in FCC process. The optimal initial-distribution of Ce ions could not only save the consumption of rare earth resources but also give the best catalytic performance of CeY zeolite catalysts, and these advantages and attributes enabled it to have the potential to be applied in industrial applications.

A rapid, low cost method for the determination of 90Sr in leaching solution of cement solidification was developed using triple-to-double coincidence ratio (TDCR) Cerenkov counting of 90Y. In this method, 90Y was separated from sample matrix and interfering radionuclides through two co-precipitation steps with hydrous titanium oxide followed by yttrium fluoride (YF3) precipitation. After dissolution of the YF3 precipitate, 90Y was measured by TDCR Cerenkov technique. The performance of the method was examined using a series of the samples spiked with various activities of 90Sr ranging from 1.75 to 32 Bq L−1, along with the procedural blanks. The mean chemical recovery of Y was 86 ± 8%. The measured 90Sr agreed well with the expected 90Sr within an acceptable deviation of ~10%. The minimum detectable concentration was about 0.3 Bq L−1 for 0.2 L sample with a counting time of 5400 s by a Hidex 300 SL TDCR liquid scintillation counter. The overall decontamination coefficients were determined to be >5400 for 60Co, >5300 for 137Cs, >14,500 for 40K and 4500 ± 580 for 210Pb/210Bi, respectively.

Flowerlike copper-doped g-C3N4 is synthesized via a novel molten salt-assisted microwave process in this work. X-ray diffraction, N2 adsorption, UV–vis spectroscopy, scanning electron microscopy, photoluminescence, temperature-programmed desorption, X-ray photoelectron spectroscopy, and electrochemical impedance spectra were used to characterize the prepared catalysts. The results show that Cu+ is not present as oxide but inserts at the interstitial position through the coordinative Cu(I)–N bonds. These Cu(I)–N active sites can act as chemical adsorption sites to activate N2 molecules. Moreover, as an “electron transfer bridge”, Cu(I)–N active sites promote electron transfer from the catalyst to the adsorbed N2 molecules. The as-prepared copper-doped g-C3N4 displays a much higher NH4+ generation rate than neat g-C3N4 prepared by calcination, as well as excellent catalytic and structural stability. Density functional theory simulations prove that Cu(I)–N active sites can adsorb the N2 molecule with high ad...

Correlation between the adsorption-transformation behaviors of 2-methylthiophene and 3-methylthiophene and the active sites of NaY, HY and rare earth ion-exchanged ultra-stable Y (REUSY) zeolites have been studied by using an in situ FTIR technique and an intelligent gravimetric analyser-mass spectrometer (IGA-MS) coupling technique. The results show that the bridging hydroxyls (OH) of Si and Al atoms located in the supercage of zeolites Y are the preferred active sites, leading to the protonation and cracking reactions of the methylthiophenes. The AlO + active sites in the HY, and the Al(OH) 2+ and RE(OH) 2+ active sites in the REUSY both can make the oligomerization reaction occur at 303 and 373 K, and especially, the RE(OH) 2+ active sites significantly improve the oligomerization abilities. Besides, the activities and selectivities of the protonated 2-methylthiophene and 3-methylthiophene play a decisive role in the oligomerization pathways. As system temperatures of > 473 K, the oligomerization reaction is restricted, while the cracking reaction is improved. Thereby, modulation of the key active sites in adsorbents and system temperatures will be a good prospect for ultra-deep desulfurization in the future.

Recently, the Furstner group reported the first general trans-hydroboration of internal alkynes by using a cationic ruthenium(II) complex, [Cp*Ru(MeCN)3]PF6, as the catalyst. Density functional theory (DFT) calculations have been carried out to elucidate the reaction mechanism and the origin of stereoselectivity. The reaction mechanism was suggested to initiate with the rate-determining oxidative hydrogen migration to stereoselectively form a metallacyclopropene intermediate (that determines the trans selectivity), followed by a reductive boryl migration to form the unusual trans-addition alkenyl-borane product. A combined ion-mobility mass spectrometry (IM-MS) and DFT study has also been employed to investigate the unsuccessful reaction with terminal alkynes. Key oxidative-coupling intermediates have been identified. Our results suggest that [2 + 2 + 2] cycloaddition of terminal alkynes to form a very stable arene compound could be the reason for the unsuccessful hydroboration of the terminal alkynes. Mo...

An oxygen-mediated annulation reaction has been reported herein. Various 3-hetero-substituted isocoumarins were successfully prepared with high efficiency (yields up to 88 %) and good functional-group tolerance (35 examples) in the presence of a rhodium catalyst. A plausible mechanism has also been proposed that shows the high regioselectivity mostly likely originates from the electron-density difference between the alkynyl carbon atoms of the substrate.

Different types of Y zeolites (HY, USY and NaY) containing various amounts of cerium (Ce) were prepared with the method of liquid ion exchange and characterized by X-ray diffraction (XRD), intelligent gravimetric analyzer (IGA), and a molecular simulation technology (grand canonical Monte Carlo simulation, GCMC). A novel calculation method of desorption index (DI) was proposed and the influence of cerium cationic species on the processes of adsorption-desorption of hydrocarbon molecules (n-octane) on the cerium modified Y zeolites (CeY) was studied. The results indicated that Ce ion species played a key role in reducing desorption activation energy of n-octane on Y type zeolites, leading to an improvement of the desorption ability of the CeY and the regulation of the adsorption state of n-octane from aggregation to decentralization. These findings are essential factors for enhancing the product selectivity of light hydrocarbon component and the catalytic activity of rare earth modified Y zeolites (REY) catalysts in fluid catalytic cracking (FCC) process.

Herein, we report, for the first time, the preparation, matrix-isolation, and spectroscopic characterization of the methyl selenyl radical and methyl-Se-nitrososelenol in combination with DFT and CASSCF/NEVPT2 computations. The latter proved to be highly photolabile, and upon irradiation with light at λ = 465 nm it leads to methyl selenyl and nitric oxide radical pairs. Upon λ > 730 nm irradiation it rearranges back to methyl-Se-nitrososelenol.

Taking advantage of the synergetic effect of confined ultrasmall metal clusters and zeolite frameworks is an efficient strategy for improving the catalytic performance of metal nanocatalysts. Herein, it is demonstrated that the synergetic effect of ultrasmall ruthenium (Ru) clusters and intrinsic Brønsted acidity of zeolite frameworks can significantly promote the hydrogen generation of ammonia borane (AB) hydrolysis. Ultrasmall Ru clusters are embedded onto the silicoaluminophosphate SAPO‐34 (CHA) and various aluminosilicate zeolites (MFI, *BEA, and FAU) with tunable acidities by a facile incipient wetness impregnation method. Evidenced by high‐resolution scanning transmission electron microscopy, the sub‐nanometric Ru clusters are uniformly distributed throughout the zeolite crystals. The X‐ray absorption spectroscopy measurements reveal the existence of Ru‐H species between Ru clusters and adjacent Brønsted acid sites of zeolites, which could synergistically activate AB and water molecules, significantly enhancing the hydrogen evolution rate of AB hydrolysis. Notably, the Ru/SAPO‐34‐0.8Si (Si/Al = 0.8) and Ru/FAU (Si/Al = 30) catalysts with strong acidities afford high turnover frequency values up to 490 and 627 min−1, respectively. These values are more than a 13‐fold enhancement than that of the commercial Ru/C catalyst, and among the top level over other heterogeneous catalysts tested under similar conditions.

A Density Functional Theory method has been employed in this research to conduct an in-depth study of the correlation between the conversion of acetylene to vinyl chloride catalysed by MCl2 (M=Hg, Cd, Zn, Mn) and the electron affinity. From the analysis of the adsorption energy and energy profile of acetylene hydrochlorination reaction, combined with Fukui indices and outer-shell Mulliken population change alongside reaction pathway, it can be concluded that, the outermost electron migration is the main factor affecting the catalytic property of MCl2 (M=Hg, Cd, Zn, Mn) catalyst. The Mulliken population change of the central atom M2+ (M=Hg, Cd, Zn) share similar tendency along the reaction pathway, the only difference is Hg2+ gained more electrons than the other two when acetylene got absorbed, and that proved that Hg(II) got better electron withdrawing, which is a main motivator of better catalytic properties in acetylene hydrochlorination reaction.

A density functional theory study has been employed to investigate the effect of next-nearest-neighbours aluminium (NNN Al) atom on the acid strength of Bronsted acid site in Y zeolite. Additionally, the distribution of NNN Al atom was also studied. The obtained results show that thermodynamically, the favourable sites for location of NNN Al atom are the diagonal sites of the four-membered ring and meta-position of hexagon I. Furthermore, the increase of NNN Al atoms causes the nonlinear reduction of the strength of Bronsted acid sites. When the number of NNN Al atoms is greater than two, the increasing extent of acid strength is not obvious with the reduction in the number of NNN Al atoms. But the acid strength will increase linearly with the further reduce of the number of NNN Al atoms. Compared with deprotonation energy (ED), ammonia adsorption energy (Eads) could give a more reasonable measuring result for the acid strength.

Three different modified SBA-15 have been synthesized by a post-grafting method using 3,4-dihydroxy benzaldehyde (OHBA), 2,4-dihydroxy benzaldehyde (MHBA), 2,4-dihydroxy acetophenone (RATP). These materials were characterized by NMR, TEM, FT-IR and elemental analysis. Batch experiments have been conducted to study the effects of pH, temperature, adsorbent dosage, ionic strength, shaking time, initial concentration of metal ion, and coexisting ions on uranium(VI) sorption behaviors of pure and functional SBA-15. In addition, the adsorption of U(VI) could be well-described by the Langmuir, Freundlich isotherms and pseudo-second kinetic models. The results suggest the sorption capacity and selectivity of SBA-15 were improved after functionalization.

Ni-Mo catalyst precursors were prepared by the precipitation method. Ni-Mo bulk hydrodesulfurization catalysts were obtained from these precursors after proper drying, molding, and calcination. The effect of polyethylene glycol (PEG) with different molecular weights and in various dosages on the structure and catalytic properties of these catalysts was investigated by applying X-ray diffraction, low-temperature BET N2 adsorption analysis, and scanning electron microscopic methods. It is shown that the structure, surface properties, and activity of the catalysts can be improved by adding PEG. The pore volume, specific surface area, and pore size of the catalysts increase gradually with increasing PEG dosage, and the dispersion of the active ingredient increases initially and then decreases.

The adsorption of ethylene on three low-index Pd–Ag bimetallic surfaces, which are the (111), (100), and (110) facets, is investigated using gradient-corrected periodic density functional calculations with dispersion correction. The surfaces have been modeled by 5 layers of Pd atoms and different Ag atomic concentrations, allowing us to study ethylene adsorption from 100% Pd to 25% Pd on the surfaces. The adsorption energy and the geometry have been computed for different adsorption sites (on top of a Pd or bridging two Pd atoms) for different facets and Ag atomic concentrations. For bare Pd surfaces and their surface alloys, the bridge site is always found to be more stable than any other site. For the surface alloys, the local density of states, charges of ethylene and Pd atom, and differential electron density have been investigated to illustrate the importance of ligand and ensemble effects of the guest metal Ag atoms. The adsorption is weakened because of the ensemble effect when the surface Ag atomic concentration increases. The amount of electrons transferred to the ethylene molecules from the surface increases slightly when the concentration of the surface atomic Ag increases. The ligand effect becomes more significant when the surface is closer, and its effect is not the same for different surface facets.

Two modified mesoporous silica (KIT-6) materials for absorbing uranium(VI) were prepared respectively via post-grafting of 8-hydroxyquinoline and 8-hydroxyquinoline onto surface of KIT-6, which were characterized by FT-IR, NMR, TEM, and sorption/desorption analysis. Effect of pH values, contact time, ionic strength, solid–liquid ratio, temperature, and coexisting ions on sorption behavior of the modified KIT-6 were also investigated. Typical sorption isotherms (Langmuir and Freundlich) were used to determine the sorption process and the maximum U(VI) sorption capacity. The results indicate that the two modified KIT-6 exhibit better selective sorption of U(VI) as compared to the original KIT-6.

Ce-containing materials attracted much attention in adsorption desulfurization due to their excellent adsorption selectivity. Identification and fabrication of specific Ce species as effective adsorption active sites, however, still remained ambiguous which had impeded the development of a potential desulfurization adsorbent. In this paper, series of CeY zeolites were synthesized via liquid phase ion exchange method. The implication of Ce loadings and calcination temperatures on the nature of Ce species active sites that can be present in the Y zeolite was a major focus of this work. Specially, the chemical speciation and location of Ce species in the CeY adsorbents were analyzed by the intelligent gravimetric analyser (IGA), XRD, in situ FTIR spectroscopy, and XPS techniques. The prepared CeY adsorbents were tested in terms of their sulfur breakthrough adsorption capacities using a fixed-bed column and model fuels. The experimental results indicate that more effective Ce(III) hydroxylated species as adsorption active sites, located in the supercages of CeY0.075C150 zeolite, are facilely fabricated as low as the calcination temperature (ca. 150 °C) and the suitable Ce loading (ca. 12.31 wt%). Remarkable sulfur breakthrough adsorption capacity can be achieved by using the new CeY0.075C150 adsorbent, which is no less ca. 5 folds than that of the reported CeY adsorbents to the best of our knowledge, especially for the 2-methylthiophene capture (ca. 18 folds). After regenerated with two cycles, the adsorbent still remains high sulfur breakthrough adsorption capacity. Importantly, this controllable method to construct specific Ce species as active sites in the CeY zeolites should play an instructive role for the development of the directional design of effective adsorption active sites in other excellent desulfurization adsorbents.

Due to the nature of Cerenkov radiation and instrumental limitations, detection efficiencies of 210Bi by Cerenkov counting are generally quite low (~15%). Sodium salicylate, acting as a wavelength shifter, has been used to improve the detection efficiency of Cerenkov photons. In this study, we found that the addition of sodium salicylate could significantly increase the counting efficiencies of 210Pb/210Bi in aqueous samples. Meanwhile, a sharp increase of the counting efficiency for the alphas from 210Po was also observed with the addition of high concentration of sodium salicylate, implying that scintillation light rather than Cerenkov photons from the alphas has been produced. Detailed studies about the effects of sodium salicylate on the counting of 210Pb, 210Bi and 210Po were conducted. At low concentration ( 1 mg g-1) of sodium salicylate would significantly increase due to the scintillation effect.

Organosulfides have great significance and value in synthetic and biological chemistry. To establish a versatile and green methodology for C–S bond generation, we successfully developed a new aerobic cross-dehydrogenative coupling of C–H and S–H to synthesize aryl sulfides in water, utilizing CoPcS as the catalyst and O2 as the oxidant. This protocol shows great tolerance of a wide range of substrates. A large variety of organosulfur compounds were produced in modest to excellent yields.

A thin-layer source for the counting of polonium isotopes by alpha spectrometry can be rapidly prepared using microprecipitation with tellurium. Polonium was first coprecipitated with the reduction of tellurium by stannous chloride, followed by microfiltration onto a membrane filter for counting. This microprecipitation method is faster, cheaper, and more convenient than the traditional spontaneous deposition method, with an excellent Po recovery (>90%) under optimal conditions. The influences of several experimental parameters, including Te(IV) quantity, reaction time, and HCl molarity, were examined to determine the optimal conditions for Te microprecipitation. The decontamination factors of potential interferences from various radionuclides (Ra, Th, U, Pu, Am) for the counting of long-lived polonium isotopes (208Po, 209Po, and 210Po) were also evaluated, and the results confirmed a good selectivity on polonium by this microprecipitation method. Due to its strong resistance to high acidity up to 12 M HC...

There is a growing demand for the determination of actinides in soil and sediment samples for environmental monitoring and tracing, radiological protection, and nuclear forensic reasons. A total sample dissolution method based on lithium metaborate fusion, followed by sequential column chromatography separation, was developed for simultaneous determination of Pu, Am and Cm isotopes in large-size environmental samples by alpha spectrometry and mass spectrometric techniques. The overall recoveries of both Pu and Am for the entire procedure were higher than 70% for large-size soil samples. The method was validated using 20 g of soil samples spiked with known amounts of 239Pu and 241Am as well as the certified reference materials IAEA-384 (Fangataufa Lagoon sediment) and IAEA-385 (Irish Sea sediment). All the measured results agreed very well with the expected values.

This letter presents the side-chain iodination of electron-deficient benzylic hydrocarbons at rt using N-hydroxyphthalimide (NHPI) as radical initiator and 1,3-diiodo-5,5-dimethylhydantoin and 3-iodo-1,5,5-trimethylhydantoin (3-ITMH) as iodine source. Addition of a carboxylic acid increased the reactivity due to complex formation with and activation of 3-ITMH by proton transfer and halogen bond formation. No SEAr reactions were observed under the employed reaction conditions. Our method enables convenient product isolation and gives 50–72% yields of isolated products.

Mesoporous γ-Al2O3 supports with different pore structures were prepared by the cation-anion double hydrolysis method. Based on these samples, MoO3/γ-Al2O3 catalysts were made via impregnation. The adsorptions of 4,6-dimethyldibenzothiophene (4,6-DMDBT) and collidine over the supports and catalysts were studied by FT-IR. The supports or catalysts with larger pores can adsorb more 4,6-DMDBT. The methyl groups on adsorbate molecules are very close to the sulfur atom, resulting in apparent steric hindrance. Increasing the pore size can promote the interaction between the adsorbates and supports or catalysts, enhancing the CC bond and weakening the CS bond of 4,6-DMDBT. 4,6-DMDBT molecules were coordinated with the unsaturated Mo atoms over the catalysts to form π-complexation adsorption. There was much difference between thiophene and 4,6-DMDBT adsorption. The adsorption of collidine over the catalysts also illustrated that there existed steric hindrance. Significantly, the catalyst with hierarchical mesopores was beneficial for the adsorbates with larger molecular dynamics diameter. Compared with the pore size, the specific surface area was not the key factor to affect the adsorptions of 4,6-DMDBT and collidine. The hydrodesulfurization reaction of 4,6-DMDBT illustrated that the catalysts with larger pore size or hierarchical pore structure presented higher desulfurization efficiency (above than 80%).

Gene Expression Programming (GEP) is an orginal and an effective searching method. Multiple Linear Regression (MLR), Artificial Neural Network (ANN) and GEP techniques were used to investigate the correlation between retention indices (RI) and descriptors for 91 oxygen-containing organic compounds. The correlation coefficient on OV-1 column is 0.9891(for ANN), 0.9919(for GEP), and 0.9911(for MLR), on SE-54 column is 0.9892(for ANN), 0.9955(for GEP), and 0.9917(for MLR). As shown from the results, the predicted values by GEP and the experimental values are in good agreement, Also, the QSRR model by GEP is better than QSRR models by ANN and MLR methods.

Iridium complexes are known catalysts for a range of silylation reactions. However, the exploitation for selective hydrosilylation of unsymmetrical internal alkynes has been limitedly known. Described here is a new example of this type. Specifically, [(cod)IrCl]2 catalyzes the efficient and mild hydrosilylation of thioalkynes by various silanes with excellent regio- and stereoselectivity. DFT studies suggested a new mechanism involving Ir(I) hydride as the key intermediate.

A metal-free trimolecular [2+2+2] cycloaddition of internal ynamides and nitriles for de novo synthesis of fully substituted pyridines is disclosed. With the versatile Bronsted acid catalyst HNTf2 , the mild intermolecular cyclotrimerization process proceeds with complementary chemoselectivity and excellent regioselectivity.