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The crumpling and buckling in nanosheets are anticipated to provide new characteristics that could not be observed in ideal flat layers. However, the rigid lattice structure of inorganic metal oxides limits their assembly into well‐defined crumpled layers. Here, this study demonstrates that at the sub‐nm scale, polyoxometalates (POMs) clusters having well‐defined structures can intercede during the nucleation process of titania and co‐assemble with nuclei to form uniform, large‐sized crumpled binary 2D layers with a thickness of 2 nm. The obtained crumpled layers are then used as a support material to immobilize Pd nanoclusters with an average size of 2 nm. Pd‐immobilized crumpled layers are employed as heterogeneous catalysts for the partial hydrogenation of acetylene. This structurally and compositionally unique heterogeneous catalyst manifests exceptional selectivity to cis‐alkene with almost 100% yield as compared to commercially available titania which only exhibits 10% diphenylacetylene conversion and 42% selectivity in the given period of time. [ABSTRACT FROM AUTHOR]

Semihydrogenation is a crucial industrial process. Noble metals such as Pd have been extensively studied in semihydrogenation reactions, owing to their unique catalytic activity toward hydrogen activation. However, the overhydrogenation of alkenes to alkanes often happens due to the rather strong adsorption of alkenes on Pd active phases. Herein, we demonstrate that the incorporation of Pd active phases as single‐atom sites in perovskite lattices such as SrTiO3 can greatly alternate the electronic structure and coordination environment of Pd active phases to facilitate the desorption of alkenes rather than further hydrogenation. Furthermore, the incorporated Pd sites can be well stabilized without sintering by a strong host–guest interaction with SrTiO3 during the activation of H species in hydrogenation reactions. As a result, the Pd incorporated SrTiO3 (Pd‐SrTiO3) exhibits an excellent time‐independent selectivity (>99.9 %) and robust durability for the photocatalytic semihydrogenation of phenylacetylene to styrene. This strategy based on incorporation of active phases in perovskite lattices will have broad implications in the development of high‐performance photocatalysts for selective hydrogenation reactions. [ABSTRACT FROM AUTHOR]

The direct construction of metal‐free catalysts on conductive substrates for electrocatalytic organic hydrogenation reactions is significant but still unexplored. Here, learning from the homogeneous molecular catalysts, an organic molecular mimetic metal‐free heterogeneous catalyst is designed and constructed in situ on a graphite flake electrode via a mild electrochemical oxidation‐reduction relay strategy. The as‐prepared −COOH‐ and −OH‐functionalized metal‐free catalyst exhibits an electrocatalytic alkyne semihydrogenation performance with a 72 % Faradaic efficiency, 99 % selectivity and 96 % yield of the alkene product, which is comparable to that of noble metal catalysts. The removal of these oxygen‐containing groups leads to negligible activity. The experimental and calculation results reveal that the origin of the high activity can be assigned to the −COOH and −OH groups on graphite. A flow electrolytic cell delivers ten grams of hydrogenated products with 81 % Faradaic efficiency. This metal‐free catalyst is also suitable for gas‐phase acetylene semihydrogenation and other electrocatalytic hydrogenation reactions. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: Alkenols are important intermediates for the industrial manufacture of various commodities and fine chemicals. At present, alkenols are produced via thermocatalytic semihydrogenation of corresponding alkynols using precious metal Pd‐based catalysts in pressurized hydrogen atmosphere. In this work, we highlight an efficient electrocatalytic strategy for selectively reducing alkynols to alkenols under ambient conditions. Using 2‐methyl‐3‐butyn‐2‐ol as a model alkynol, Cu3P nanoarrays anchored on Cu foam remarkably deliver an industrial‐level partial current density of 0.79 A·cm–2 and a specific selectivity of 98% for 2‐methyl‐3‐buten‐2‐ol in acidic solution. Over a 40‐runs stability test, Cu3P nanoarrays maintain 90% alkynol conversion and 90% alkenol selectivity. Even in a large two‐electrode flow electrolyser, the single‐pass alkynol conversion and alkenol selectivity of Cu3P nanoarrays exceed 90%. Moreover, this selective electrocatalytic hydrogenation approach is broadly feasible for the production of various water‐soluble alkenols. Electrochemical analyses, theoretical simulation and electrochemical in‐situ infrared investigations together reveal that exothermic alkynol hydrogenation, facile alkenol desorption and formation of active H on Cu3P surfaces account for the excellent electrocatalytic performance. [ABSTRACT FROM AUTHOR]

Electrochemical alkyne reduction with H 2 O as a hydrogen source represents a sustainable route for value-added olefin production. However, the reaction efficiency is hampered by the high voltage and low activity of Cu electrodes due to their weak adsorbed hydrogen (*H) generation property. In this article, we present the enhanced electrocatalysis of phenylacetylene to styrene over a highly dispersive Cr-doped Cu 2 O nanowire (Cr-Cu 2 O) cathode. The Cr-Cu 2 O demonstrates improved catalytic activity compared to pure Cu 2 O, achieving a high conversion of about 94.7% and a selectivity of 87.9% with a Faraday efficiency of 64.5% at a low potential of -1.15 V vs Hg/HgO. The combination of electrochemical characterization techniques and theoretical calculations demonstrated the key role of introduced Cr atoms in lowering the activation energy barrier of surface water electrolysis to *H and facilitating the adsorption of phenylacetylene, which promotes the effective hydrogenation of phenylacetylene with *H via an electrocatalytic hydrogenation mechanism. In short, this work provides a feasible strategy to enrich interfacial *H, thus improving the semihydrogenation performance of phenylacetylene.

Silicon carbide (SiC)-supported palladium (Pd) catalysts [3% Pd/SiC and a 3% Pd-diethylenetriamine (DETA)/SiC complex] for chemoselective hydrogenation under batch- and continuous-flow conditions were developed. The alkyne, alkene, azide, nitro, and benzyloxycarbonyl-protected aromatic amine (N-Cbz) functionalities were chemoselectively reduced in the presence of 3% Pd/SiC. By contrast, benzyl ether, alkyl N-Cbz, epoxide, aromatic chloride, aromatic ketone, and tert-butyldimethylsilyl ether were tolerant to the 3% Pd/SiC-catalyzed hydrogenation. The combined use of 3% Pd/SiC and DETA demonstrated excellent chemoselectivity toward the semihydrogenation of various mono- and disubstituted alkynes under batch- and continuous-flow conditions. Furthermore, compared with the separate use of 3% Pd/SiC and DETA, the newly developed 3% Pd(DETA)/SiC-packed in a cartridge showed higher chemoselectivity toward the continuous-flow semihydrogenation of alkyne over 24 h. [ABSTRACT FROM AUTHOR]

It is challenging to establish single metal atoms with a uniform coordination environment at targeted sites of a zeolite. In this study, single platinum atoms were selectively encaged in the six‐membered rings of sodalite (SOD) cages within Y zeolite using a template‐guiding strategy. During the in situ synthesis process, template molecules were designed to occupy supercages and thereby force coordinated platinum species into SOD cages. Subsequent control of the post‐treatment conditions yielded the Y zeolite with selectively encaged single platinum atoms, denoted Pt@Y‐SOD. The Pt@Y‐SOD catalyst had good stability and excellent catalytic selectivity in the semihydrogenation reaction, and it exhibited interesting thiophene and carbon monoxide resistance in this transformation because interactions with these poisons are weakened by the configuration of the encaged single platinum atoms. [ABSTRACT FROM AUTHOR]

We recently disclosed a dehydrogenative double C−H bond activation reaction in the unusual pincer‐type rhodium‐germyl complex [(ArMes)2ClGeRh] (ArMes=C6H3‐2,6‐(C6H2‐2,4,6‐Me3)2). Herein we investigate the catalytic applications of this Rh/Ge system in several transformations, namely trans‐semihydrogenation of internal alkynes, trans‐isomerization of olefins and hydrosilylation of alkynes. We have compared the activity and selectivity of this catalyst against other common rhodium precursors, as well as related sterically hindered rhodium complexes, being the one with the germyl fragment superior in terms of selectivity towards E‐isomers. To increase this selectivity, a tandem catalytic protocol that incorporates the use of a heterogeneous catalyst for the trans‐semihydrogenation of internal alkynes has been devised. Kinetic mechanistic investigations provide important information regarding the individual catalytic cycles that comprise the overall trans‐semihydrogenation of internal alkynes. [ABSTRACT FROM AUTHOR]

[Display omitted] • 2D MoSe 2 nanomesh catalyst decorated with Pd particles in the highly ordered nanopores was synthesized. • Highly ordered nanopores were important structures for improving catalytic activity. • The DFT calculations confirmed that the Pd@MoSe 2 nanomesh had a weaker attraction for alkenes and the C atoms in alkenes had less negative charges on the Pd@MoSe 2 nanomesh surface. • Calculations and experimental results showed that the Pd@MoSe 2 nanomesh exhibited excellent catalytic performance for semihydrogenation of alkynes. The performance of catalysts determines the selectivity and yield of the products in most semihydrogenation of alkynes. Herein, we design a two-dimensional (2D) MoSe 2 nanomesh catalyst decorated with Pd particles in the nanopores. The designed 2D-Pd@MoSe 2 nanomesh catalyst exhibits 99 % conversion of alkynes and 99 % selectivity in semihydrogenation due to its highly exposed active sites, the higher hydrogenation barrier, and lower desorption energy provided by suitable Pd-Se bond interactions. Further in situ characterizations and density functional theory (DFT) calculations confirm that the Pd@MoSe 2 nanomesh has a weaker attraction for alkenes (E des = 0.36 eV) and the C atoms in alkenes have less negative charges on the Pd@MoSe 2 nanomesh surface (−0.139 e), resulting in an increased reaction barrier for alkene overhydrogenation. This research provides new insight for improving the catalytic performance of 2D transition metal dichalcogenides catalysts in the chemical industry. [ABSTRACT FROM AUTHOR]

A palladium-catalyzed semihydrogenation of alkynes to E - and Z -alkenes employing EtOH as the hydrogenating agent is reported. The selectivity of the reaction system was effectively controlled by -ligand/additive and solvent regulation. The use of sodium acetate/-triethanolamine (NaOAc/TEOA), THF, and (1 R ,2 R)-bis[(2--methoxyphenyl)phenylphosphino]ethane [(R , R)-DIPAMP] in CH3 CN was critical for the stereoselective semihydrogenation of alkynes. The general applicability of this procedure was highlighted by the synthesis of more than 36 alkenes, in good yields with high stereoselectivities. [ABSTRACT FROM AUTHOR]

Two iridium disilyl complexes that contain phosphine‐pendant silyl groups have been obtained from the reaction of [(cod)IrCl]2 with a disilane with phosphine pendants, (Ph2PCH2)R2Si−SiR2(CH2PPh) (R=Me or Ph). The iridium complex with methyl‐substituted silyl moieties showed good catalytic performance in the (E)‐selective semihydrogenation of various alkynes at room temperature under 1 atm of H2 without over‐reduction to the corresponding alkanes. [ABSTRACT FROM AUTHOR]

We reported mesoporosity engineering as a general strategy to promote semihydrogenation selectivity of palladium (Pd)‐based nanobundles catalysts. The best mesoporous PdP displayed full conversion, remarkable activity, excellent selectivity, and high stability in semihydrogenation of 1‐phenyl‐1‐propyne, all of which are remarkably better than commercial Lindlar catalysts. Mechanistic investigations ascribed high semihydrogenation selectivity to the continuous crystalline framework and penetrated mesoporous channel of catalysts that weakened the adsorption and interaction capacity of alkenes and thus inhibited over‐hydrogenation of alkenes to industrially unfavorable alkanes. Density functional theory calculations further demonstrated that convex crystalline mesoporosity of nanobundles catalysts electronically optimized the coordination environment of Pd active sites and energetically changed hydrogenation trends, resulting in a superior semihydrogenation selectivity to targeted alkenes. [ABSTRACT FROM AUTHOR]

Owing to its applicability in sustainable engineering, flow electrochemical synthesis in a proton-exchange membrane (PEM) reactor has attracted considerable attention. Because the reactions in PEM reactors are performed under electro-organic and flow-synthetic conditions, a higher number of reaction parameters exist compared to ordinary reactions. Thus, the optimization of such reactions requires significant amounts of energy, time, chemical and human resources. Herein, we show that the optimization of alkyne semihydrogenation in PEM reactors can be facilitated by means of Bayesian optimization, an applied mathematics strategy. Applying the optimized conditions, we also demonstrate the generation of a deuterated Z-alkene.

Selective reduction strategies based on abundant‐metal catalysts are very important in the production of chemicals. In this paper, a method for the electrochemical semihydrogenation and semideuteration of alkynes to form Z‐alkenes was developed, using a simple nickel foam as catalyst and H3O+ or D3O+ as sources of hydrogen or deuterium. Good yields and excellent stereoselectivities (Z/E up to 20 : 1) were obtained under very mild reaction conditions. The reaction proceeded with terminal and nonterminal alkynes, and also with alkynes containing easily reducible functional groups, such as carbonyl groups, as well as aryl chlorides, bromides, and even iodides. The nickel‐foam electrocatalyst could be recycled up to 14 times without any change in its catalytic properties. [ABSTRACT FROM AUTHOR]

In this study, with zeolite HY as support, ultrasmall Pd and Pt nanoparticles were successfully immobilized into zeolite HY crystals through an optimized impregnation approach. The success of this new approach mainly relied on the selecting appropriate metal precursor to make Pd and Pt element exists with the cation forms, which can facilitate their diffusion into inner channels of zeolite HY through electrostatic attraction and capillary force. Integration of confinement effect of zeolite HY, taking zeolite HY (Si/Al = 3) encapsulation of ultrasmall Pd NPs (Pd@HY-3) as an instance, Pd@HY-3 catalyst exhibited enhanced catalytic selectivity in semihydrogenation of alkynes, in comparison with Pd/HY, Pd/C, Pd/Al2O3 and lindlar catalysts. This improved catalytic selectivity can be attributed to the constrained upright adsorption conformation of reactant alkyne and corresponding product alkene on encapsulated Pd surface to make alkyne adsorption on Pd surface with larger adsorption energy than that of alkene, thus achieving the high catalytic selectivity. [ABSTRACT FROM AUTHOR]

Metal halide perovskite materials with excellent carrier transport properties have been regarded as a new class of catalysts with great application potential. However, their development is hampered by their instability in polar solvents and high temperatures. Herein, we report a solution-processed Cs 2 MoCl 6 perovskite nanocrystals (NCs) capped with the Mo 6+ , showing high thermostability in polar solvents. Furthermore, the Pd single atoms (PdSA) can be anchored on the surface of Cs 2 MoCl 6 NCs through the unique coordination structure of Pd-Cl sites, which exhibit excellent semihydrogenation of different alkyne derivatives with high selectivity at full conversion at room temperature. Moreover, the activity could be improved greatly under Xe lamp irradiation. Detailed experimental characterization and DFT calculations indicate the improved activity under light illumination is due to the synergistic effect of photo-to-heat conversion and photoinduced electron transfer from Cs 2 MoCl 6 to PdSA, which facilitates the activation of the C≡C group. This work not only provides a new catalyst for high selective semihydrogenation of alkyne derivatives but also opens a new avenue for metal halides as photothermal catalysts.

The ideal interface design between the metal and substrate is crucial in determining the overall performance of the alkyne semihydrogenation reaction. Single-atom alloys (SAAs) with isolated dispersed active centers are ideal media for the study of reaction effects. Herein, a charge-asymmetry "armor" SAA (named Pd 1 Fe SAA@PC), which consists of a Pd 1 Fe alloy core and a semiconducting P-doped C (PC) shell, is rationally designed as an ideal catalyst for the selective hydrogenation of alkynes with high efficiency. Multiple spectroscopic analyses and density functional theory calculations have demonstrated that Pd 1 Fe SAA@PC is dual-regulated by lattice tensile and Schottky effects, which govern the selectivity and activity of hydrogenation, respectively. (1) The PC shell layer applied an external traction force causing a 1.2% tensile strain inside the Pd 1 Fe alloy to increase the reaction selectivity. (2) P doping into the C-shell layer realized a transition from a p-type semiconductor to an n-type semiconductor, thereby forming a unique Schottky junction for advancing alkyne semihydrogenation activity. The dual regulation of lattice strain and the Schottky effect ensures the excellent performance of Pd 1 Fe SAA@PC in the semihydrogenation reaction of phenylethylene, achieving a conversion rate of 99.9% and a selectivity of 98.9% at 4 min. These well-defined interface modulation strategies offer a practical approach for the rational design and performance optimization of semihydrogenation catalysts.

Supported single-atom catalysts have become one of the most exciting frontiers in heterogeneous catalysis. The physicochemical properties of these materials are highly interesting; however, the generation of stable single atoms on solid supports is still challenging. Herein, we report an efficient and operationally simple postsynthesis method, consisting of spatial confining, freeze-drying, and reducing steps, for the construction of singly dispersed palladium atoms on SAPO-31 (Pd1/SAPO-31) with promising application prospects in the semihydrogenation of alkynes. A typical Pd–N–C single-atom catalyst derived from the ZIF-8-supported palladium complex was prepared and compared to Pd1/SAPO-31. The Pd1/SAPO-31 catalyst showed outstanding performance in the semihydrogenation of both phenylacetylene (85% selectivity at 99% conversion, 40 min) and 1-chloro-4-ethynylbenzene (95% selectivity at 99% conversion, 60 min). In addition, this single-atom palladium catalyst was highly active in triethoxysilane oxidation. Most importantly, this catalyst retained its atomic dispersion and catalytic activity after high-temperature thermal treatment in Ar at 700 °C. This study demonstrates how zeolites can be used to confine atomically dispersed metal species and tune the activity and stability of these materials to meet the needs of practical applications. [ABSTRACT FROM AUTHOR]

We reported a selective semihydrogenation (deuteration) of numerous terminal and internal alkynes using H2O (D2O) as the H (D) source over a Pd‐P alloy cathode at a lower potential. P‐doping caused the enhanced specific adsorption of alkynes and the promoted intrinsic activity for producing adsorbed atomic hydrogen (H*ads) from water electrolysis. The semihydrogenation of alkynes could be accomplished at a lower potential with up to 99 % selectivity and 78 % Faraday efficiency of alkene products, outperforming pure Pd and commercial Pd/C. This electrochemical semihydrogenation of alkynes might proceed via a H*ads addition pathway rather than a proton‐coupled electron transfer process. The decreased amount of H*ads at a lower potential and the more preferential adsorption of the Pd‐P to C≡C π bond than C=C moiety resulted in the excellent alkene selectivity. This method was capable of producing mono‐, di‐, and tri‐deuterated alkenes with up to 99 % deuterium incorporation. [ABSTRACT FROM AUTHOR]

Supported metal nanoparticles are a very large class of heterogeneous catalysts. While detailed structure–activity relationships require a molecular‐level description of the interactions between the metal surfaces and ligands/substrates, this description is rarely accessible. Thus, most insights are derived from models based on single crystals. With the goal to understand alkyne semihydrogenation catalysts based on Cu functionalized with N‐heterocyclic carbene (NHC), we cross this gap by investigating NHC‐stabilized molecular complexes, supported single sites and nanoparticles by solid‐state NMR combined with computations. We show that in silica‐supported Cu single sites, Cu retains the coordination geometry observed in molecular compounds, while, for supported Cu nanoparticles, which are active and selective for the semihydrogenation of alkynes, NHC binding is favored at Cu adatoms atop of copper surface, thus paralleling conclusions of surface science studies on single crystals. [ABSTRACT FROM AUTHOR]

Selective hydrogenation of alkynes to alkenes (semihydrogenation) without the use of a poison and H2 is challenging because alkenes are easily hydrogenated to alkanes. In this study, a titanium (IV) oxide photocatalyst having Pd core‐Cu shell nanoparticles (Pd@Cu/TiO2) was prepared by using the two‐step photodeposition method, and Pd@Cu/TiO2 samples having various Cu contents were characterized by electron transmission microscopy, X‐ray photoelectron spectroscopy and UV‐vis spectroscopy. Thus‐prepared Pd@Cu/TiO2 samples were used for photocatalytic hydrogenation of 4‐octyne in alcohol and the catalytic properties were compared with those of Pd/TiO2 and Cu/TiO2. 4‐Octyne was fully hydrogenated to octane over Pd/TiO2 at a high rate and 4‐octyne was semihydrogenated to cis‐4‐octene over Cu/TiO2 at a low rate. Rapid semihydrogenation of 4‐octyne was achieved over Pd(0.2 mol%)@Cu(1.0 mol%)/TiO2, indicating that the Pd core greatly activated the Cu shell that acted as reaction sites. A slight increase in the reaction temperature greatly increased the rate with a suppressed rate of H2 evolution as the side reaction. Changes in the reaction rates of the main and side reactions are discussed on the basis of results of kinetic studies. Reusability and expandability of Pd@Cu/TiO2 in semihydrogenation are also discussed. [ABSTRACT FROM AUTHOR]

Selective hydrogenation of nitriles and alkynes is crucial considering the vast applications of reduced products in industries and in the synthesis of bioactive compounds. Particularly, the late 3d transition metal catalysts (manganese, iron, cobalt, nickel and copper) have shown promising activity for the hydrogenation of nitriles to primary amines, secondary amines and imines. Similarly, semihydrogenation of alkynes to E- and Z-alkenes by 3d metals is adequately successful both via the transfer hydrogenation and by using molecular hydrogen. The emergence of 3d transition metals in the selective synthesis of industrially relevant amines, imines and alkenes makes this protocol more attractive. Herein, we provide a concise overview on the late 3d transition metal-catalyzed hydrogenation of nitriles to amines and imines as well as semihydrogenation of alkynes to alkenes. [ABSTRACT FROM AUTHOR]

Herein, the first example of visible‐light‐driven, cobalt‐catalyzed transfer semihydrogenation of alkynes to alkenes is reported. It is carried out by using Ir[dF(CF3)ppy]2(dtbbpy)]PF6 as photosensitizer, CoBr2/n‐Bu3P as proton‐reducing catalyst, and i‐Pr2NEt/AcOH as the hydrogen source. Under the established catalytic system, the semihydrogenation proceeds with Z as the major selectivity and with inhibition of over‐reduction. Under mild reaction conditions, both internal and terminal alkynes, as well as reducible functional groups such as halogen, cyano, and ester, are tolerated. Preliminary mechanistic studies revealed the dual role of the photosensitizer in initiating the reaction via a single‐electron transfer process and controlling the stereoselectivity via an energy transfer process. [ABSTRACT FROM AUTHOR]

Intermetallic compounds (IMCs) composed of transition metals and post‐transition metals function as superior heterogeneous catalysts in comparison to their monometallic and bimetallic alloy counterparts. Rendering IMCs in their nanomaterial iterations further enhances their efficiency. Herein, we demonstrate the role of PdIn as well‐dispersed intermetallic nanoparticles (IMNPs) for the semihydrogenation of phenylacetylene selectively to styrene at ambient conditions. Higher selectivity of PdIn was explained with the help DOS calculations. We have explored the role of a few well‐known silica‐based supports such as SBA‐15 and MCM‐41, providing insight into how they affect catalysis. As an additional support we have explored previously reported JNC‐1, a mesoporous carbon material obtained via a templated strategy using SBA‐15. PdIn supported on SBA‐15 and JNC‐1 displayed the best dispersion, while also exhibiting the most catalytic activity due to the unique nature of the porous structure. [ABSTRACT FROM AUTHOR]

• H 2 and O 2 were produced at separate times in water-organic solvent systems. • H 4 SiW 12 O 40 was an efficient electron-coupled-proton buffer in the present systems. • Organic solvents could regulate the redox property of silicotungstic acid in water. • A high yield of hydrogen (∼85%) was obtained in a water-ethanol system (V/V = 1:1). • Semihydrogenation of organic compounds could be achieved under mild conditions. H 2 and O 2 were produced at separate times from water electrolysis by using silicotungstic acid as an electron-coupled-proton buffer. It was found that the redox property of silicotungstic acid in water could be regulate by the introduction of organic solvents (acetonitrile, DMF and ethanol). The redox wave of silicotungstic acid at ∼0.02 V vs. RHE moved in the negative direction, which was good for the production of hydrogen. A high yield of hydrogen (∼85%) was obtained in a water-ethanol system (V/V = 1:1), which was higher than that in water (∼45%). And the introduction of ethanol didn't affect the rate of hydrogen evolution. Moreover, the semihydrogenation of organic compounds could be achieved in the present system under mild conditions. The conversion of phenylacetylene and acetophenone are 97% and 80% under optimum reaction conditions, while the selectivity of styrene and 1-phenylethanol are 80% and 82%, respectively. [ABSTRACT FROM AUTHOR]

• TiO 2 photocatalyst modified with 2,3-dihydroxynaphthalene (DHN) responded to visible light. • DHN/TiO 2 -Cu converted alkynes to cis -alkenes under H 2 -free and poison-free conditions. • Water in acetonitrile affected alkyne adsorption and catalytic performance. • Catalytic hydrogenation process over Cu was the rate-determining step. • Reaction temperature controlled selectivity of hydrogenation and H 2 evolution. Hydrogen (H 2)-free and poison (lead and quinoline)-free semihydrogenation of alkynes to cis -alkenes under gentle conditions is one of the challenges to be solved. In this study, a titanium(IV) oxide photocatalyst having two functions (visible light responsiveness and semihydrogenation activity) was prepared by modification with 2,3-dihydroxynaphthalene (DHN) and a copper (Cu) co-catalyst, respectively. The photocatalyst (DHN/TiO 2 -Cu) showed high performance for diastereoselective semihydrogenation of alkynes to cis -alkenes in water-acetonitrile solution under visible light irradiation without the use of H 2 and poisons. Alkynes having reducible functional groups were converted to the corresponding alkenes with the functional groups being preserved. The addition of water to acetonitrile changed the amount of alkynes adsorbed on the photocatalyst, which was a decisive factor determining the rate of hydrogenation. A relatively large apparent activation energy, 27 kJ mol−1, was obtained by a kinetic study, indicating that the rate-determining step of this reaction was not an electron production process but a thermal catalytic semihydrogenation process over the Cu co-catalyst. Semihydrogenation and hydrogen evolution occurred competitively on Cu metals and the former became predominant at slightly elevated temperatures, which is discussed on the basis of the kinetic parameters of two reactions. [ABSTRACT FROM AUTHOR]

A highly efficient heterogeneous palladium-catalyzed transfer semihydrogenation of internal alkynes was achieved in dimethylformamide at 145 ºC by using an MCM-41-immobilized bidentate nitrogen palladium(II) complex [MCM-41-2N-Pd(OAc)2] as catalyst and dimethylformamide/KOH as hydrogen source, yielding a variety of cis -alkenes in good to high yields with excellent stereoselectivity. This supported palladium catalyst can be easily recovered by filtration of the reaction solution and recycled up to seven times with almost consistent activity. [ABSTRACT FROM AUTHOR]

In this work, an effective and versatile modification approach of palladium (Pd)/nitrogen doped carbon by iron series element for the semihydrogenation of phenylacetylene is presented. Pd and iron series element M (M=Fe, Co or Ni) particles were co‐reduced and supported on nitrogen‐doped activated carbon (Pd−M/NC). Experimental results showed that the Pd−M/NC exhibited relatively good catalytic performance when the Pd/M content mass ratio was approximately 1 : 1. The selectivity of styrene could be maintained at relatively good levels even with the prolongation of reaction time. The good catalytic effect of the Pd−M/NC may be attributed to the incorporation of iron series element species. The catalysts had been characterized in detail and contrastive study was made to validate the modification effect. The catalyst could maintain its catalytic activity and selectivity in the recycle process. This work may show industrial application potentiality and developing directions in selective hydrogenation process. Pd does it again! The modification of palladium/nitrogen‐doped carbon with iron series elements M (M=Fe, Co or Ni) species promoted the selectivity for the semihydrogenation of phenylacetylene to styrene. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The Ni particle size of Ni/AlSBA-15 can be tuned by adjusting the Al content. • Semihydrogenation of phenylacetylene (PA) over Ni/AlSBA-15 is structure-sensitive. • NiZn and NiGa alloys were formed on AlSBA-15 supported bimetallic catalysts. • NiZn 3 /AlSBA-15 showed 90.3% selectivity to styrene at nearly 100% conversion of PA. • NiZn 3 /AlSBA-15 displayed stable activity and selectivity over 100 h on-stream. Abstract A series of nonprecious monometallic Ni/AlSBA-15 and bimetallic Ni M (M = Zn, Ga, Cu, or Fe)/AlSBA-15 catalysts were prepared using a urea precipitation method and applied to the semihydrogenation of phenylacetylene. The catalysts were characterized by various techniques, showing that the Ni particle size of catalyst can be tuned by adjusting the Al content, and NiZn and NiGa supported catalysts exhibited geometric and electronic effects that originated from the bimetallic alloy. Among all the catalysts studied, NiZn 3 /AlSBA-15, with a turnover frequency of 10.89 s−1 comparable to that of precious Pd-based catalysts, presented the highest selectivity to styrene (90.3%) at nearly 100% conversion of phenylacetylene in semibatch operation. This catalyst was further evaluated in a continuous fixed-bed reactor for semihydrogenation of a model C 8 aromatic fraction of pyrolysis gasoline (a mixture of phenylacetylene, styrene, ethylbenzene and xylene), which aimed at assessing its practical application of recovering styrene from pyrolysis gasoline. The results showed that at complete conversion of phenylacetylene, the styrene concentration in the product was always kept at a stable level and higher than its initial concentration over 100 h of time on stream, demonstrating high selectivity and good stability of NiZn 3 /AlSBA-15. Finally, the application of NiZn 3 /AlSBA-15 was extended to other phenylacetylene derivatives. [ABSTRACT FROM AUTHOR]

• Synthesis of atomically dispersed alloyed PtCu ZSM-5 supported catalyst (PtCuOx/Z). • Synthesis of PtCo nanoclusters ZSM-5 supported catalyst (PtCoOx/Z). • Semihydrogenation activity and selectivity measurement of PtCuOx/Z and PtCuOx/Z. • In situ XANES and EXAFS characterization of PtCuOx/Z and PtCuOx/Z. • Computation and experimental results showed that PtCuOx/Z has better C 2 H 4 selectivity. In this study, we focused on the semihydrogenation of acetylene (SHA) in an ethylene-rich stream to produce clean ethylene (devoid of acetylene that poisons the ethylene polymerization catalysts) as an incentive to increase polymer production. Two alloyed Pt catalysts namely PtCu and PtCo were synthesized via functionalization with oxalate ligands and supported on ZSM-5 (PtCuOx/Z and PtCoOx/Z), characterized, and tested for the SHA under a typical industrial condition. While there are instances of single-atom Pt alloyed with Cu in the PtCuOx/Z catalyst, nanoclusters of alloyed Pt and Co prevailed in PtCoOx/Z according to the EXAFS and HAADF-STEM results. Threshold energies ( E 0 ) of 11566.8 and 11563.8 eV obtained from the first derivative of the XANES spectra were observed for PtCuOx/Z and PtCoOx/Z, respectively under experimental conditions. Accordingly, the high E 0 implied a higher unoccupied density of Pt d -orbital which is a key indicator for enhanced SHA activity leading to a higher ethylene yield ( Y C2H4) of 87.6 % over PtCuOx/Z compared to 62.9 % over PtCoOx/Z at 200 °C. These results were confirmed by a DFT computation which showed that Pt in the catalysts contains more electrons in PtCuOx/Z than in PtCoOx/Z, thus shifting the d -band center downward of the Fermi level in the former than the latter which allows only a weakly π-bonded C 2 H 4 that desorbs before the secondary reactions leading to high Y C2H4 , while PtCoOx/Z favor higher Y C2H6. This result showed that alloying Pt with Cu is more promising in synthesizing industrial relevant SHA catalyst. [ABSTRACT FROM AUTHOR]

The promoting effect of sulfur sources is an intriguing but poorly understood phenomenon. Herein, we studied the treatment of PdCu bimetallic nanoparticles (NPs) with different amounts of sulfur powder. Low-level sulfidation led to the generation of a Pd30Cu10S9 NP catalyst consisting of surface enriched Pd NPs, electron deficient Pd and Cu, as well as zero valence sulfur. The Pd30Cu10S9 NP catalyst showed pronouncedly enhanced activity and selectivity in the semihydrogenation of alkynes. Our study revealed for the first time a possible cause for the promoting effect of sulfur at the atomic level, suggesting a new strategy in catalyst design. [ABSTRACT FROM AUTHOR]

A method for the preparation of mixed AuPd nanoparticles that are used as catalysts for selective alkyne Z‐semihydrogenation is described. It is shown that the corresponding monometallic Pd nanoparticles display a lower activity, documenting the cooperative effect exerted by the two metals. These mixed AuPd nanoalloys are readily prepared by irradiation of the corresponding precursor salts in the presence of photoactive polymers or commercially available photoinitiators as reducing and stabilizing agents. Alkyne semihydrogenation using these catalyst systems with H2 proceeds in high yield (up to 97 % yield of isolated product) and excellent Z‐selectivity (up to 99 %). Hydrogenations work on larger scale and the hybrid catalyst can be recovered and reused by simple centrifugation. [ABSTRACT FROM AUTHOR]

The heterogeneous nanocatalyst based on palladium (Pd) is one of the most preferable choices for catalytic hydrogenation reactions as the adsorption and dissociation of hydrogen molecules (H2) are almost spontaneous on Pd surface to form the adsorbed H atoms (Had). However, in terms of alkyne semihydrogenation, it remains a grand challenge to optimize both the activity and selectivity of reactions using bare Pd catalysts as the case is largely complicated by the excessive Had produced from rapid H2 dissociation and the strong Pd-H binding. In this communication, a well-designed model is developed for seeking a selective semihydrogenation catalyst based on surface lattice engineering. In the proposed model, the ultrathin atomic layer of AuPd shell is grown on the Au nanocubes. The Au nanocubes provide specific facets as substrates for hosting catalytic sites, which can also provide information for further lattice engineering design. While Pd atoms are the active centers for hydrogenation reactions in the nanostructures, alloying Pd atoms with Au in the shells can significantly alter the binding of Had to metals. As such, the activity and selectivity in catalytic alkyne semihydrogenation can be substantially maneuvered by tailoring the atomic arrangement of Pd and Au on surface. As a proof of concept, the Au@AuPd nanocatalyst with a surface Pd/Au ratio of 1:4 achieves a 98.9% semihydrogenation selectivity with a conversion of 98.2% in the 2-methyl-3-butyn-2-ol (MBY) hydrogenation reaction. [ABSTRACT FROM AUTHOR]

Abstract: Chemoselective semihydrogenation of alkynes to alkenes is a significant organic transformation and long challenge for heterogeneous catalysts. Herein, the PdAu alloyed nanoparticles were successfully deposited on the surface of cerium(IV) oxide nanorods (NR‐CeO2) through an electroless chemical deposition process. Alloyed catalysts had an enhanced catalytic activity for hydrogenation of phenylacetylene and improved selectivity towards styrene, compared with the Pd/NR‐CeO2 and Au/NR‐CeO2 catalysts. The enhanced catalytic activity can be attributed to the alloying effects. Furthermore, the weak adsorption of styrene obtained from the modulated surface characteristics also benefits the improved chemoselectivity. [ABSTRACT FROM AUTHOR]

The chemoselective semihydrogenation of alkynes is one of the most important reactions in synthetic organic chemistry. During the last decade or so, a multitude of innovative catalytic methods have been developed to address the selective hydrogenation of alkynes. This digest focuses on the recent developments in chemoselective semihydrogenation of alkynes to alkenes. [ABSTRACT FROM AUTHOR]

A simple and straightforward semihydrogenation of alkyne to alkene with triethanolamine and formic acid in the presence of PdCl 2 has been described. Although hydrogenation using formic acid as a hydrogenation source has been used in combination with amines previously, few reports are available concerning the associated reactivity. We demonstrated that reactivity changes depending on the type of amine used in the hydrogenation. Further, this reaction requires no strict time control, making it a useful tool in organic synthesis. [ABSTRACT FROM AUTHOR]

Highly dispersed palladium nanoparticles (Pd NPs) immobilized on heteroatom-doped hierarchical porous carbon supports (N,O-carbon) with large specific surface areas are synthesized by a wet chemical reduction method. The N,O-carbon derived from naturally abundant bamboo shoots is fabricated by a tandem hydrothermal-carbonization process without assistance of any templates, chemical activation reagents, or exogenous N or O sources in a simple and ecofriendly manner. The prepared Pd/N,O-carbon catalyst shows extremely high activity and excellent chemoselectivity for semihydrogenation of a broad range of alkynes to versatile and valuable alkenes under ambient conditions. The catalyst can be readily recovered for successive reuse with negligible loss in activity and selectivity, and is also applicable for practical gram-scale reactions. [ABSTRACT FROM AUTHOR]

The influence of different thiol ligands on the activity and particularly the stability of colloidal platinum nanoparticles is studied by using the catalytic semihydrogenation of 3-hexyne as model reaction. It is shown that a reduced ligand concentration during functionalization leads to an increase in the catalyst activity, while the stability of the particles as colloids in solution is surprisingly maintained, which also holds for the selectivity. Furthermore, it is demonstrated that the concept of reduced ligand coverages can also be applied to different thiol-based surfactants with varying steric demands. As shown for cyclohexanethiol-capped platinum nanoparticles, after eight recycling runs the particles maintain their activity and selectivity in all cycles. Electron microscopy further confirms that the particle size is preserved after the catalytic runs. [ABSTRACT FROM AUTHOR]

Palladium nanoparticles immobilized on hollow carbon nanospheres introduced with both Fe and N species, denoted as Pd/Fe-N/C, have been designed as an efficient, heterogeneous, environmentally friendly catalyst for the semihydrogenation of phenylacetylene in liquid-phase under mild conditions (298 K, H 2 1 atm) without any additive. A high selectivity towards styrene (higher than 96.2%) was achieved with the total conversion of phenylacetylene within 80 min. The synergistic effect of doped N and Fe with Pd might be an important influence on improving the catalytic performance. Moreover, the Pd/Fe-N/C could be easily recycled by centrifugation and is reusable without obvious decrease of catalytic activity and selectivity. Therefore, the Pd/Fe-N/C nanocatalyst is highly attractive as selective hydrogenation heterogeneous catalyst for important industrial reactions. [ABSTRACT FROM AUTHOR]

Pd 0 nanoparticles (NPs) have been fabricated on SBA-15 using a facile, rapid and highly reproducible microwave-assisted reduction by solvent method. The as-synthesized Pd@SBA-15 nanocomposite was well characterized using low angle and wide angle XRD, TEM, FE-SEM, N 2 adsorption-desorption isotherm, FTIR, XPS etc. The Pd@SBA-15 nanocomposite act as an active, recyclable heterogeneous catalyst for semihydrogenation of phenylacetylene under solvent-free mild reaction conditions (303 K, atmospheric H 2 ). A maximum of 94.4% phenylacetylene conversion was achieved with very high selectivity for styrene (95.5%). Moreover, the used catalyst was recovered by centrifugation and reused up to four times without significant loss in their catalytic activity. This optimized reaction protocol for phenylacetylene was also well performed in case of various other alkynes with similar or better performance. [ABSTRACT FROM AUTHOR]

[Display omitted] • Metal phosphides@carbon was synthesized using a new polymeric phosphorus source. • Different metal phosphides@carbon catalyst can be synthesized by this method. • This catalyst exhibited excellent catalytic performance for selective hydrogenation. • This catalyst showed high anti-sulfur poisoning and anti-acid corrosion capability. A universal strategy to synthesize metal phosphides (MPs, M = Ni, Co, Cu, Fe, Pd, Pt, Ru) nanoparticles encapsulated in 2D defect-rich graphitic carbon shell (MPs@C-PPS) using P- and C-rich polymeric phosphide (PPS) as the precursor was brought out. Characterization results demonstrate that the thickness of the carbon shell on different MPs nanoparticles ranges from 1 to 7 nm, which can be adjusted by changing the Ni/P molar ratio. Some cracks and irregular defects are observed in carbon layers, which can selectively permeate small hydrogen molecules and block the passage of larger organic molecules. In catalytic performance test, the as-synthesized Ni 2 P@C-PPS exhibited excellent selectivity in alkynes semihydrogenation and high anti-sulfur poisoning and anti-acid corrosion capability in hydrogenation reactions. Mechanism exploration indicates that selective permeability of the carbon shell is the key to improving catalyst robustness. [ABSTRACT FROM AUTHOR]

A 2.5 wt.% Pd/ZnO catalytic coating has been deposited onto the inner wall of capillary reactors with a diameter of 0.53 and 1.6 mm. The coatings were characterised by XRD, SEM, TEM and elemental analysis. The performance of catalytic reactors was studied in solvent-free hydrogenation of 2-methyl-3-butyn-2-ol. No mass transfer limitations was observed in the reactor with a diameter of 0.53 mm up to a catalyst loading of 1.0 kg (Pd) m −3 . The activity and selectivity of the catalysts has been studied in a batch reactor to develop a kinetic model. The kinetic model was combined with the reactor model to describe the obtained data in a wide range of reaction conditions. The model was applied to calculate the range of reaction conditions to reach a production rate of liquid product of 10–50 kg a day in a single catalytic capillary reactor. [ABSTRACT FROM AUTHOR]