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ZIF-8 and ZIF-67 containing various percentages of copper were successfully synthesized through a green in-situ thermal (IST) approach based on 2-methylimidazole (2-MIM) as the organic linker. The IST method has several advantages over previously reported studies, including solvent and additive-free reaction conditions, a mild reaction temperature, a single-step procedure, no activation requirements, and the use of the smallest precursor ratio (M/L). The high catalytic performance of Cu/ZIF-8 and Cu/ZIF-67 in click chemistry is attributed to their high specific surface area, excellent porosity, and structural stability. To achieve these features, a range of parameters—such as time, temperature, gas atmosphere, and precursor ratio—were optimized. Several characterization methods were used to confirm the features of the produced catalysts. Overall, the synthesis strategy for achieving the targeted ZIFs with unique features is "green" and does not require further activation or treatment to eliminate side products. This method has great potential for manufacturing metal-organic frameworks on a large scale. Moreover, water was used as a solvent during the click reaction, resulting in high yields and making this an attractive, green, and eco-friendly procedure. [ABSTRACT FROM AUTHOR]

Biosensors featuring single molecule detection present huge opportunities as well as challenges in food safety inspection, disease diagnosis, and environmental monitoring. Single‐molecule detection is largely lacking of high enough activity, precision molecule selectivity, and understanding in the exact operating mechanism. Single‐atom catalysts (SACs), especially those metals‐nitrogen‐carbon that mimic the natural metalloenzyme structure, and with well‐defined metal atom bond configurations, high level of molecular selectivity, and easy fabrication, endow single molecule detections with practical‐use feasibilities. The recent advances in single‐atom catalysts also present new pathways in the key mechanism understandings. In this short review, we will first visit the brief history and advantages of SACs that have been explored only recently for molecule‐scale biosensors, where they are analogous and also differentiated from those nanozymes and natural metalloenzymes. Their applications in electrochemical, photochemical, and photoelectrochemical sensors are then discussed comprehensively by focusing on the different molecule‐scale sensing modes in achieving local coordination‐modulated signal amplifications. Finally, we identify new opportunities and challenges faced by these SACs‐based single molecule detections in the further development of biosensors. [ABSTRACT FROM AUTHOR]

Here, for the first time, a 2D and leaf-like zeolitic imidazolate framework (ZIF-L) is reported for the synthesis of ultrahigh molecular weight (UHMW) poly(methyl methacrylate) (PMMA) with Mn up to 1390 kg mol−1. This synthesis method is a one-step process without any co-catalyst in a solvent-free medium. SEM, PXRD, FT-IR, TGA, and nitrogen sorption measurements confirmed the 2D and leaf-like structure of ZIF-L. The results of PXRD, SEM, TGA demonstrate that the catalyst ZIF-L is remarkably stable even after a long-time polymerization reaction. Zwitterionic Lewis pair polymerization (LPP) has been proposed for the catalytic performance of ZIF-L on methyl methacrylate (MMA) polymerization. This MMA polymerization is consistent with a living system, where ZIF-L could reinitiate the polymerization and propagates the process by gradually growing the polymer chains. [ABSTRACT FROM AUTHOR]

Nitrogen-doped porous carbon material was generated via thermal pyrolysis of zeolitic imidazole frameworks (ZIFs). The structure of the ZIF templates was tuned, so that the obtained product was an N-doped porous carbon-containing encapsulated metal nanoparticle. The hierarchical structural and unique properties of pyrolyzed materials are involved in further application, including catalysis. The as-synthesized porous carbon materials were applied as a catalyst for CO2 fixation on cyclic carbonates under near ambient pressure without solvent and co-catalyst. The zinc dispersion in highly porous carbon material, deriving from ZIF-8, exhibited a superior catalytic performance among the synthesized materials. The acid sites (Zn species) and the incorporated basic sites (N-species) present in the porous carbon material are essential for a high affinity for gas adsorption and CO2 conversion. Additionally, the catalyst was found to be very robust and stable during recycling studies as the catalytic performance remained high for seven cycles. [ABSTRACT FROM AUTHOR]

Molecular catalysts are acknowledged for the ability to design reaction sites within well‐defined structures to achieve high catalytic activities. However, in many cases, molecular catalysts undergo structural changes to some other form(s), which are finally the real catalysts. Here, we report two half‐sandwich ruthenium complexes; [Ru([9]aneN3)(bpy)Cl]+3 and [Ru([9]aneN3)(pic)OH2]2+4, based on the macrocyclic 1,4,7‐triazacyclononane ([9]aneN3) ligand for water oxidation (WO). The two complexes have similar core but different ancillary ligands, which greatly affected their stability as well as activity for WO. Complex 3 retained high stability and excellent activity (turnover number [TON] = 1250) in chemical WO and first‐order reaction kinetics with respect to [CeIV] with a calculated rate constant (kcat) of 34.59 s−1. Further, the complex demonstrated very low overpotential of ~210 mV in electrochemical WO. At an overpotential of only 400 mV, turnover frequency (TOF) of complex 3 was electrochemically estimated to be 131.2 s−1. In contrast, complex 4 underwent picolinate ligand dissociation, as a deactivation pathway, to form the tri‐aqua derivative. Density functional theory (DFT) calculations are used to explain the dissociation mechanism of picolinate ligand in complex 4, which happens through a stepwise dissociation mechanism. [ABSTRACT FROM AUTHOR]

Hydroxymethylfurfural (5‐HMF) is a vital biomass‐derived platform chemical for the production of secondary value‐added chemicals. In this work, fructose conversion into 5‐HMF over metal–organic framework (MOF) has been considered. Several MOF‐based catalysts were synthesized and examined in fructose dehydration into 5‐HMF via a microwave‐assisted reactor. Each MOF's catalytic performance was evaluated concerning its surface area, pore size, and acid density. The results showed satisfactory fructose conversion levels for all studied MOFs in the range of 60%–99%. As a catalyst, zeolitic imidazolate frameworks (ZIFs) resulted in excellent fructose conversion, but interestingly, higher quantities of side products such as formic and levulinic acids were produced. The higher 5‐HMF yields, up to 90%, were obtained over the MIL‐101 (MIL, Materials Institute Lavoisier) family, such as MIL‐101‐SO3H. This result is ascribed to the fact that functionalized MOF possesses hydrothermal stability, high surface area, and suitable pore sizes. [ABSTRACT FROM AUTHOR]

Here, one‐step synthesis of high molecular weight poly(methyl methacrylate) (PMMA; 1000–1650 kg mol−1) is reported by using zeolitic imidazole framework‐8 (ZIF‐8) catalyst without any co‐catalyst in the absence of a solvent. This type of high molecular weight PMMA has different applications, mainly in gel polymer electrolyte and bone cement. Zwitterionic type mechanism is proposed where the active acid site of the catalyst dominates for initiation of polymerization. Without any significance loss of structural morphology and catalytic activity, ZIF‐8 can easily be recycled for further uses. ZIF‐8 exhibits superior activities for the synthesis of high molecular weight PMMA compared to the heterogeneous catalysts mentioned earlier. [ABSTRACT FROM AUTHOR]

In this review, we have portrayed the structure, synthesis and applications of a variety of biomimetic MOFs from an unprecedented angle. Synthetic MOF analogues of five distinct enzymes: phosphotriesterase, hydrogenase, cytochrome P450, chymotrypsin and carbonic anhydrase, have been discussed with their skeletal comparison to actual enzymatic active sites as reference, and an explanation of catalytic pathways from the mechanistic cycle of the corresponding enzymes is depicted. We demonstrated critically each of the five discrete situations by assimilating available benchmark researches in an attempt to provide a concise literature source on the ingenious design strategies and versatile biomimetic applications of this domain of materials. [ABSTRACT FROM AUTHOR]

Zeolitic imidazole framework (ZIF)-67 is an efficient heterogeneous catalyst for the cycloaddition of carbon dioxide to epoxides to afford cyclic carbonates. In this work, ZIF-67 was synthesized by a simple and straightforward method at room temperature. The coupling reaction in the presence of ZIF-67 without any co-catalyst or solvent was studied under different conditions. The reaction conversion was more than 99% and the selectivity toward chloropropene carbonate was considerably higher (＞99%) than the previously reported ZIF-8. Moreover, the ZIF-67 catalyst could be recycled at least four times without noticeable loss of catalytic activity. [ABSTRACT FROM AUTHOR]

For several decades olefin metathesis reactions over supported Mo, W, and Re oxides catalysts have attracted remarkable interest owning to their growing industrial applications. Therefore, particular attention was devoted to improve the catalytic activity of these catalysts. In the way of exploration of the catalytic performances of these heterogeneous Mo, W, and Re oxides systems, it was found that high dispersion of metal oxide on the support surface and the oxidation state of the metal oxide on the surface of catalyst play crucial factors on the catalysts efficiency. Importantly, these factors have an origin in the preparation methods and the properties of the used supports. In this regard, we have tried to address the various preparation methods of immobilized Mo, W, and Re oxide catalysts as well as properties of supporting material to better understand their impacts on the catalytic performances of these catalysts. [ABSTRACT FROM PUBLISHER]

is a transition metal-mediated transformation that rearranges the carbon atoms of the carbon-carbon double bond of olefins. This reaction has become one of the most important and powerful reactions. Therefore development of new, well-defined, highly active and selective catalysts is very desirable and a valuable goal. This mini-review mainly introduces the development of ruthenium catalysts in highlighting oxygen-chelated indenylidene ruthenium catalysts. Applying an alkoxyl group on the indenylidene ligand fragment can generate the Ru O chelating bond. Additionally, various modifications of the ligand as well as the for ring-closing and selectivity of cross are overviewed. Finally, the perspectives on the development of new catalysts are summarized. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The catalytic nature of self-assembled metal-organic polyhedra gives an entirely new dimension to the reactivity and properties of molecules within a well-defined confined space. Encapsulation of a range of guests brings about not only host-guest interactions but also gives rise to unusual reactivities with selectivity and stabilization of various reactive intermediates. This review briefly covers the synthesis of self-assembled metal-organic polyhedra and elaborates their influence in different chemical reactions as well as in the stabilization of unstable chemical species. [ABSTRACT FROM AUTHOR]

Pincer-based catalysts possess an exceptional balance of stability versus reactivity, aspects of fundamental interest in catalyst design. This balance has been well-controlled by systematic ligand modifications along with the variation of the metal center. Ruthenium pincer complexes (RPCs), exhibit a versatile chemistry, serve as excellent precursors and find potential applications in many organic transformations. A large number of novel and valuable reactions has been developed using both stoichiometric and catalytic amounts of RPCs. Compared to the traditional ruthenium catalysts, pincer complexes often present high efficiency, selectivity and functional group tolerance. This review highlights different methodologies for the synthesis of RPCs and their catalytic applications for different reactions reported in the last decade. Additionally, the factors affecting the catalytic reactivity of the RPCs and the reaction mechanisms are discussed. [ABSTRACT FROM AUTHOR]

Aiming at improving catalyst activity, ten ruthenium promoters have been investigated in carbenoid transfer from ethyl diazoacetate to styrene as a model substrate. Optimal selectivity in cyclopropanation has been attained with the new NHC-Ru complex 10, as well as with the Fischer carbene 7. The surprising non-metathetical behavior of the Grubbs' first-generation catalyst in this multifaceted process is highlighted. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The cover image is based on the Full Paper I Metal-organic frameworks as catalysts for fructose conversion into 5-hydroxymethylfurfural: Catalyst screening and parametric study i by Noor Aljammal et al., https://doi.org/10.1002/aoc.6419. GLO:O7E/01dec21:aoc6533-toc-0001.jpg PHOTO (COLOR): . gl. [Extracted from the article]

Abstract: Pt-loaded H-beta zeolite was identified as a highly active catalyst for the bifunctional transformation of citronellal to menthol, with isopulegol as the intermediate. With a 2 wt% Pt-loaded catalyst, citronellal is fully converted within 12 h, with only 2.5 wt% catalyst with respect to citronellal, and with a citronellal to Pt molar ratio of 2500. -Dioxane is the best reaction solvent, because it minimizes the unwanted direct hydrogenation of citronellal and promotes its stereoselective cyclization to isopulegol, leading to high menthol yields. The stereoselectivity can be improved moderately by using a Zr-impregnated support and more substantially by performing high-temperature (750 °C) treatment of the calcined and reduced catalyst. This treatment presumably creates extra Lewis acidity on the catalyst and results in 88% stereoselectivity for the desired menthol. Overall, an 85% yield of (–)-menthol was obtained. [Copyright &y& Elsevier]

We now report the synthesis and characterization of a new class of N-heterocyclic carbene (NHC) and Schiff base containing ruthenium complexes and their performance as catalysts in atom transfer radical addition and enol ester synthesis reactions. The ruthenium Schiff base complexes 3a–f mediated the atom transfer radical addition (ATRA) of carbon tetrachloride across olefins in excellent yields which markedly depended on the catalyst and the substrate used. Furthermore, dependant on the catalytic system and the reaction conditions used, enol esters or enynes can be obtained in excellent yields with very high selectivities. [Copyright &y& Elsevier]

The present paper describes a greener sustainable route toward the synthesis of NIPHUs. We report a highly efficient solvent-free process to produce [4,4′-bi(1,3-dioxolane)]-2,2′-dione (BDC), involving CO2, as renewable feedstock, and bis-epoxide (1,3-butadiendiepoxide) using only metal–organic frameworks (MOFs) as catalysts and cetyltrimethyl-ammonium bromide (CTAB) as a co-catalyst. This synthetic procedure is evaluated in the context of reducing global emissions of waste CO2 and converting CO2 into useful chemical feedstocks. The reaction was carried out in a pressurized reactor at pressures of 30 bars and controlled temperatures of around 120–130 °C. This study examines how reaction parameters such as catalyst used, temperature, or reaction time can influence the molar mass, yield, or reactivity of BDC. High BDC reactivity is essential for producing high molar mass linear non-isocyanate polyhydroxyurethane (NIPHU) via melt-phase polyaddition with aliphatic diamines. The optimized Al-OH-fumarate catalyst system described in this paper exhibited a 78% GC-MS conversion for the desired cyclic carbonates, in the absence of a solvent and a 50 wt % chemically fixed CO2. The cycloaddition reaction could also be carried out in the absence of CTAB, although lower cyclic carbonate yields were observed. [ABSTRACT FROM AUTHOR]

The cutting-edge photovoltaic cells are an indispensable part of the ongoing progress of earth-friendly plans for daily life energy consumption. However, the continuous electrical demand that extends to the nighttime requires a prior deployment of efficient real-time storage systems. In this regard, metal-air batteries have presented themselves as the most suitable candidates for solar energy storage, combining extra lightweight with higher power outputs and promises of longer life cycles. Scientific research over non-precious functional catalysts has always been the milestone and still contributing significantly to exploring new advanced materials and moderating the cost of both complementary technologies. Metal-organic frameworks (MOFs)-derived functional materials have found their way to the application as storage and conversion materials, owing to their structural variety, porous advantages, as well as the tunability and high reactivity. In this review, we provide a detailed overview of the latest progress of MOF-based materials operating in metal-air batteries and photovoltaic cells. [ABSTRACT FROM AUTHOR]

A series of spray dried zeolitic imidazolate frameworks (ZIFs = ZIF‐8, ZIF‐67, and Zn/Co‐ZIF) are used as a catalyst for the bulk ring‐opening polymerization of δ‐valerolactone without any co‐catalyst to generate polyvalerolactone. Interestingly, using the same catalyst under the same reaction conditions could manipulate the structure of the product polymer, and thus its physical properties. Thus, using a dried substrate leads to the formation of the cyclic polymer while a linear polymer was formed on using the commercially available substrate. An activated monomer mechanism has been suggested where the propagating zinc alkoxide undergoes an intramolecular transesterification to release cyclic or linear polyvalerolactone. The ROP of δ‐VL without drying shows that the polymeric zwitterions have little tendency to cyclize in the presence of moisture. At 140 °C, ZIF‐8 shows a superior catalytic activity resulting in the production of cyclic polyvalerolactone having a high molecular weight as compared to ZIF‐67 or Zn/Co‐ZIF due to the presence of highly active sites. The catalyst could be recycled and reused without any significant loss of catalytic activity. [ABSTRACT FROM AUTHOR]

The facile synthesis of composite material, combining magnetic CoO with ZIF-67 (CoO@ZIF-67), has been successfully developed. This innovative approach involves the growth of a crystalline (ZIF-67) derived from stable and abundant CoO, resulting in the formation of the composite magnetic CoO@ZIF-67. The synthesis method, based on a solid-state thermal approach (SST), is straightforward and efficient, conducted in a single step and under solvent-free conditions, leading to the homogeneously composite formation of CoO@ZIF-67. Importantly, the composite magnetic CoO@ZIF-67 material has demonstrated remarkable catalytic performance as a heterogeneous catalyst in various reactions while requiring a lower catalyst loading under comparable conditions to those needed for pure ZIF-67. A significant advantage of this newly developed composite catalyst, CoO@ZIF-67, is its ease of separation and recyclability. The recovery catalyst can be achieved through the use of an external magnet, making it a standout feature of the green and environmentally friendly synthetic procedure used in its production. [Display omitted] • New straightforward and efficient synthesis of magnetic CoO@ZIF-67 as a core-shell composite material. • Solid-state thermal (SST) to synthesize CoO@ZIF-67 advantages as a single-step, solvent-free, and mild conditions. • Composite core-shell magnetism CoO@ZIF-67 exhibits excellent catalytic performance in various reactions. • Distinctive CoO@ZIF-67 material simplifies reaction as robust and magnetic composite catalysts. [ABSTRACT FROM AUTHOR]

Racemization of chirally stable secondary alcohols was performed using a truly heterogeneous catalyst under mild reaction conditions in the absence of any additive or cocatalyst. The catalyst is based on Ru3+ immobilized on calcium hydroxyapatite (Ru–HAP). The preparation of the calcium hydroxyapatite (HAP) support and the Ru content and immobilization were optimized leading to maximal catalytic performance. Via combined XRD, Raman, SEM, XPS, EPR, N2 adsorption, and ICP analysis, information on both the compositional and the structural properties of the material was obtained. The Ru–HAP catalyst is able to racemize benzylic as well as aliphatic secondary alcohols. The catalyst scope was further investigated for racemization of several mono- and polyfunctional secondary alcohols. Performing standard racemization of a reference substrate in the presence of a functional additive demonstrated the inhibitory effect of some of these functions. Finally the heterogeneous nature of the catalyst was verified by filtrate tests. [Copyright &y& Elsevier]

Two solid catalysts in which a Schiff base containing ruthenium complex has been covalently anchored on MCM-41 have been prepared and characterized. The catalytic behavior of these materials in ring-closing metathesis (RCM), ring-opening metathesis polymerization (ROMP), Kharasch addition, atom transfer radical polymerization (ATRP) and vinylation reactions as well as the recycling characteristics in RCM reactions are presented to exemplify the effectiveness and the multifunctional character of these catalytic systems. For ROMP the influence of the polymerization solvent on the performance of the catalysts was checked. For the RCM reactions both reaction time and reaction temperature were varied in order to determine the influence of these parameters on the RCM activity of our catalysts. The activity of our catalytic systems in radical reactions such as ATRP and the Kharasch addition is promising. Our results demonstrate that the ATRP process of styrene proceeds in a controlled fashion allowing the synthesis of well-defined polymers. Furthermore, we were able to demonstrate that the Kharasch activity of our catalysts shows a pronounced temperature dependence. In addition to all this, we also postulated a mechanism that explains for the observed selectivities in the vinylation experiments. The host–guest interaction of these hybrid catalytic systems is studied by XRD, XRF, ICP/MS, BET, FT-Raman and solid state NMR analysis. [Copyright &y& Elsevier]

• The core-structure UiO-66 combined with shell-structure UiO-67-BPY was explored. • Palladium (Pd) was selected for the selective metal incorporation. • Excellent Pd-dispersion via coordination with the bipyridinic groups was obtained. • Pd-UiO-67-BPY@UiO-66 showed excellent conversions for catalytic olefin hydrogenation. • Pd-UiO-67-BPY@UiO-66 demonstrated ~2.8 times higher activity than Pd-UiO-67-BPY. Facile strategies for noble metal dispersion in the shell-layer of core–shell structured metal–organic frameworks based on Zr-MOFs (UiO-66@Pd-UiO-67-BPY) was developed. The robust structure of the core-structure UiO-66 was firstly synthesized before covering up with a shell-structure of UiO-67-BPY obtaining the core–shell structure (UiO-66@UiO-67-BPY). The metallation with active palladium species (PdII) was designed on the shell-layer of core–shell MOFs via a post-synthetic method. The Pd species were coordinated explicitly in a bidentate manner to the bipyridyl linkers of the shell-structure (UiO-67-BPY). Excellent dispersion of Pd in the shell structure was obtained, resulting in UiO-66@Pd-UiO-67-BPY, as confirmed from characterizations. Taking advantage of the designed catalyst, the synthesized UiO-66@Pd-UiO-67-BPY was examined for the catalytic hydrogenation reaction. The results revealed an excellent catalytic performance of UiO-66@Pd-UiO-67-BPY compared with the traditional catalyst Pd-UiO-67-BPY. Moreover, the designed catalyst structure exhibited outstanding performance and paved the way towards a cost-effective catalyst synthesis based on MOFs combined with a noble metal. [ABSTRACT FROM AUTHOR]

• Hydrazone-based ONO pincer mono-nuclear Al complexes were synthesized and characterized. • These ONO-pincer Al-complexes are excellent catalyst for the fixation of CO 2. • The coupling was catalyzed at atmospheric pressure with the highest conversion. • For the mechanistic investigation intermediate species were detected. Carbon dioxide, the main cause of environmental pollution, its utilization to produce valuable products is of utmost interest. A series ONO pincer hydrazone based most active mono-nuclear Al(III) complexes were successfully synthesized and characterized with the help of NMR, IR, mass spectrometry and only complex 2a was confirmed by single-crystal analysis. The synthesized Al(III) complexes were then employed as capable catalysts for the solvent-free chemical fixation of CO 2 with epoxides at atmospheric pressure and could be reused five times without loss of any catalytic activity. In addition, the catalytic mechanism was investigated by analyzing intermediates via 1H NMR, 13C NMR, and mass MALDI-TOF. The excellent catalytic performance could be due to simultaneous attack and the opening of the epoxide by metal centers to form an alkoxide ion which activates the CO 2 the same time. [ABSTRACT FROM AUTHOR]

• Direct harnessing of Vis-to-near-IR light energy by a novel semiconducting azobenzene-based colloidal porous organic polymer. • Mesoporous nano-sized particles of the obtained organic network manifested excellent Pd(II) coordinating ability. • Substantial efficiency of heterogeneous semiconductor → Pd(II) energy transfer for Sonogashira coupling. • Possible reaction mechanism for photo-mediated Sonogashira coupling catalyzed by Pd-B 3 -Azo 4 is proposed. We herein report the direct harnessing of visible light energy by a novel semiconducting azobenzene-based colloidal porous organic polymer, B 3 -Azo 4 amenable to post-synthetic Pd(II)-complexation for photo-induced Sonogashira coupling using polymer → metal energy transfer process. Completely mesoporous nano-sized particles of the obtained organic network manifested excellent Pd(II) coordinating ability and afforded desired catalytic products at room temperature under aerobic condition in aqueous medium. The protocol remained valid for different aromatic and aliphatic substrates as well. A possible reaction mechanism for photo-mediated Sonogashira coupling catalyzed by Pd-B 3 -Azo 4 is also proposed. [ABSTRACT FROM AUTHOR]

3D metal N-doped carbon frameworks (M-NCFs) are produced from the direct pyrolysis of 2D zeolitic imidazolate frameworks (ZIF-L Zn and Co) in a reducing atmosphere. The effects of the thermal treatment were studied in order to achieve the desired catalyst. The results show that metal nanoparticles and N-doping species present in the carbon matrix have a direct influence on the catalytic performance. Zn/NCF-1000 displayed quantitative conversion and selectivity towards the chemical fixation of carbon dioxide through the cycloaddition with epoxides. Furthermore, the magnetic property of the newly synthesized Co/NCF-600 was used to demonstrate its superior stability and recyclability, retaining the same catalytic activity for more than 10 cycles. Image 1 • 3D Zn/NCFs and Co/NCFs derived from 2D ZIF-L crystals were easily prepared. • Comparative study of the different M/NCFs as function of the thermal treatment. • Zn/NCF-1000 and Co/NCF-600 are excellent catalysts for CO 2 fixation. • Enhanced structural stability ensures 10 recycles without activity loss. [ABSTRACT FROM AUTHOR]

Abstract Partially and fully sulfonated UiO66 derivatives, along with the non-functionalized MOF, were synthetized by one-step solvothermal synthesis. Structural, acid and porous properties were investigated before and after dehydration and thermal activation processes. Hydrated, dehydrated and thermally activated materials were screened as a heterogeneous catalyst towards the esterification of levulinic acid with ethanol in order to determine the effects of the exposed acid functionalities amount and hydration. The hydrated fully sulfonated UiO66 presented the highest activity and resulted to be more efficient than commercial Amberlyst 15. It also demonstrated high stability and recyclability in consecutive reaction runs. Graphical abstract Unlabelled Image [ABSTRACT FROM AUTHOR]

[Display omitted] • Fundamentals and metrics for evaluation of CO 2 reduction reaction (CO 2 RR) electrocatalysts. • Pioneering and recent examples of pincer-based molecular catalysts in CO 2 RR. • Effect of ligand structure, metal type, and reaction conditions on product selectivity and catalysts' stabilities in CO 2 RR. • Heterogenization of pincer-based molecular catalysts for CO 2 RR, and its impact on reduction products. • Mechanistic understanding of CO 2 RR using pincer-based molecular catalysts. Transforming wastes or hazardous materials into value-added chemical products is of great concern from economic, environmental, and sustainable prospects. Various approaches were implemented to convert CO 2 into valuable/fine chemicals, e.g., chemical fixation, electro-, thermal-, and photo-catalysis. The electrochemical reduction pathway of CO 2 stands as the most promising one with its multiple advantages and the growing abundance of renewable sources of electricity. Though heterogeneous catalysts are advantageous for their robustness and recyclability, molecular catalysts are well-established for controlling and designing reaction sites within well-defined structures for a better understanding of catalytic reaction pathways. The straightforward modifications of pincer-type ligands, along with their robust chelation, pre-designed geometries, and redox activities, make pincer-based molecular catalysts of broad worthy interest in molecular catalysis. Thus, the primary aim of this review is to focus on the application of pincer-type complexes in CO 2 reduction reaction (CO 2 RR) that are being widely investigated and have provided stimulating findings about reaction mechanisms, reactive intermediates, deactivation pathways, etc. The insights gained from these studies have the potential to drive the development of catalysts of high selectivity and reasonable stability at low overpotential and high reaction rates. The product selectivity is generally controlled by the central transition metal , where CO, syngas (CO + H 2 mixture), and formate are the most frequent products of most reported pincer-based catalysts. However, modulating the pincer ligand structure could also switch product selectivity. A simple modification in the ligand motif(s) can significantly change the reaction mechanism and catalytic rates. We have also discussed the reaction mechanisms by which the reaction products are formed as well as the stability issues of these catalysts. Finally, some examples of immobilized molecular pincer catalysts for CO 2 RR are highlighted. It is obvious that introducing a variety of metals and manipulating the coordination sites in the pincer ligands still require further detailed investigations, so that this field may lead to fulfilling the demands of global scientific and technological prosperity. [ABSTRACT FROM AUTHOR]

The article focuses on the preparation of ruthenium olefin metathesis catalysts featuring a ruthenium-carbon double bond and on alternative ruthenium-based olefin metathesis catalysts derived from alkyne precursors. It discusses the efforts toward the efficient preparation of ruthenium complexes bearing an alkylidene ligand that are related to the field of olefin metathesis. Green catalysis of allenylidene ruthenium complexes is also discussed.

Abstract: Kinetics of ring-opening metathesis polymerization (ROMP) of exo,exo-5,6-di(methoxycarbonyl)-7-oxabicyclo[2.2.1]hept-2-ene, promoted by the Grubbs’ 1st generation precatalyst, has been effectively monitored by FT-Raman and NMR spectroscopy. Both techniques evidenced similar monomer conversions to be attained under the same reaction conditions. The present FT-Raman study provided information on the polymer steric configuration, the Raman bands at 1670 and 1677cm−1 being specifically assigned to stretching vibrations of double bonds from the cis- and trans-polymer, respectively. The trans/cis ratio observed by FT-Raman parallels the corresponding result from 1H NMR. For the first time, a comparison was made on application of these complementary methods on the same ROMP reaction, evidencing their assets and disadvantages and reliability of FT-Raman. [Copyright &y& Elsevier]

Abstract: The hydrogenation of the α,β-unsaturated aldehydes cinnamaldehyde (trans-3-phenyl-2-propenal), citral (3,7-dimethyl-2,6-octadienal) and leaf aldehyde (trans-2-hexenal) was investigated with metal colloids as quasihomogeneous catalysts in organic solvents. Using polyvinylpyrrolidone-stabilized Ag0 and Co0 nanoclusters, the carbonyl compounds were chemoselectively hydrogenated to the desired allylic alcohol fragrances. Particularly the Ag0 nanosols emerged as a worthwhile alternative for Pt or Ru based catalysts. Amides proved to be excellent solvents for the synthesis as well as for the application of the metal nanocolloids in the hydrogenation of α,β-unsaturated aldehydes. In the challenging hydrogenation of citral, a selectivity exceeding 70% towards the doubly unsaturated alcohol isomers (geraniol and nerol) was attained at 90% conversion using Ag0 nanocolloids dispersed in N,N-dimethylacetamide. Reactions were performed under mild conditions (2.0MPa H2, 323K) at a molar citral/silver ratio of 200/1. The addition of Lewis acid cations, such as Fe3+ or Zn2+ resulted in a further improvement of the catalytic activity and chemoselectivity. Finally, by application of membrane filtrations, an efficient separation of the metallic nanocolloids from the reaction mixtures was realized. In the recycling of the metal nanosols, the metal catalysts’ nanodispersion and performance were satisfactorily preserved. [Copyright &y& Elsevier]

Abstract: The synthesis and characterisation of Schiff base substituted second generation Grubbs catalysts is described using the pyridine functionalised second generation catalyst and a Schiff base-Tl salt. The complexes are less active for the ROMP of COD (cycloocadiene) than their second generation analogues though their activity for the ROMP of DCPD (dicyclopentadiene) at high temperatures shows great potential due to the thermal stability of the catalysts. [Copyright &y& Elsevier]

Abstract: This study describes the qualitative analysis of the polymerization reaction of DCPD (DiCycloPentaDiene) and its reaction products. The polymerization was carried out using WCl6/Si(allyl)4 (1), first generation Grubbs’ (2) and second generation Grubbs’ (3) catalysts. When system 1 was used as a catalyst, solution concentration determined whether soluble or insoluble polymer was obtained. When Grubbs’ catalysts were employed, insoluble polymer was formed in all cases. The ring opening metathesis polymerization (ROMP)-reaction and the resulting polymers were monitored in situ via FT-Raman-spectroscopy. Using FT-Raman-spectroscopy, the stereospecific nature of the forming polymer can be determined during the polymerization reaction. The obtained spectra illustrate that the linear polymer has a prevailing cis double bond configuration, while the polymer formed using the 1e generation Grubbs catalyst has a predominant trans double bond configuration. The second generation Grubbs catalyst exhibits a poor stereoselectivity. These results are in accordance to literature data where the stereospecific nature of these polymers where determined using NMR-spectroscopy. [Copyright &y& Elsevier]

The use of high-throughput synthesis and screening techniques is demonstrated with the optimization of and the search for new antimony-rich mixed-metal oxide catalysts for the selective oxidation of isobutane to methacrolein. Three 207-member catalyst libraries have been prepared via a sol-gel synthesis procedure using design software and a synthesis robot. The catalyst libraries have been examined for catalytic activity and selectivity using spatially resolved mass spectrometry in an open-well reactor system. The reaction products have been detected by mass spectrometry and the massive data obtained have been analyzed with the help of dedicated software. Using a composition spread approach, an optimal composition of Mo–V–Sb catalysts has been identified. Screening of 68 combinations of other antimony-rich mixed oxides on libraries provides evidence that the Mo–V–Sb system is a unique ternary composition for selective oxidation of isobutane to methacrolein. Scale up of the combinatorially interesting compositions confirmed unequivocally their excellent catalytic behavior. [Copyright &y& Elsevier]

Thermal treatment of Ru-alkylidene (4) bearing a triazol-5-ylidene (NHC) ligand (2) at 110 °C and addition of a terminal alkyne generates a ruthenium vinylidene. The thermolysed Ru-alkylidene catalyses the vinylation and dimerisation of 1-alkynes. The nucleophilic addition of acetic acid on terminal alkynes proceeds smoothly and regioselective towards the Markovnikov addition. The addition reaction can be tuned by changing the acidity of the carboxylic acid. At increasing acidity, higher conversion of the triple bond is obtained and the vinylation/dimerisation ratio increases. The direct coupling between two 1-alkynes shows a reactivity order, which decreases from 1-octyne>1,7-octadiyne>phenylacetylene>3,3 dimethyl-1-butyne. The regioselectivity is strongly dependent on the nature of the terminal alkyne. [Copyright &y& Elsevier]

Diesel soot oxidation over Au–VOx/TiO2 and Au–VOx/ZrO2 catalytic systems with different vanadia loadings were studied. The heavy-duty diesel soot was preliminarily analyzed. The composition of the catalysts was investigated by means of FT–Raman. Their activity toward the oxidation of diesel soot was assessed by thermogravimetrical analysis. The combustion onset temperature and the combustion peak maximum can be lowered to 361 and 419°C, respectively. Reaction rates R at certain temperature Tr are calculated out of the first derivative from the mass loss in function of temperature (TGA plot). The results of the activity tests indicate a synergistic effect between Aunanoparticles and vanadia when VOx presents as a monolayer on the support. Catalysts with higher V loadings show a higher activity but no synergistic effects between Au and V could be observed. [Copyright &y& Elsevier]

[Display omitted] The synthesis and characterization of a novel latent ruthenium catalyst bearing a chelate ligand containing an oxadiazole fragment for the olefin metathesis are described. The main advantages of the utilization of this ligand are the straightforwardness of preparation, mild reaction conditions, and availability of the feedstock. Preliminary study of the catalytic activity of the Ru complex for metathesis reactions demonstrated its inactive nature for the ring-closing metathesis (RCM), but an excellent thermo-switchability for the ring-opening metathesis polymerization of norbornene. [ABSTRACT FROM AUTHOR]

• ZnO dispersed in an N-doped carbon matrix (ZnO/NCs) was derived from thermal treatment of Zn-DABCO. • The ZnO/NCs catalysts showed excellent activity towards the polymerization of ε-caprolactone. • The acid and basic sites present in the ZnO/NCs co-operatively catalyze the polymerization. • The ZnO/NCs catalyst produces high molecular weight cyclic polycaprolactone (c-PCL). • The catalyst retained its stability and activity after being used for at least seven cycles. For the first time, ZnO dispersed in an N-doped carbon matrix (ZnO/NCs) was derived from the controlled thermal treatment of Zn-DABCO and utilized as a robust heterogeneous catalyst for the polymerization of ε-caprolactone. The as-prepared ZnO/NCs catalysts were characterized using TEM, SEM, Raman spectroscopy, XPS, XRD, TPD and N 2 adsorption. The catalyst displayed excellent activity towards the ε-caprolactone polymerization reaction, following the trend, Zn/NC-1000 < Zn/NC-800 < Zn/NC-600. The polymerization was catalyzed co-operatively by both acid and basic sites present in the ZnO/NCs, leading to high molecular weight cyclic polycaprolactone (c-PCL). Furthermore, the catalyst retained its stability and activity after being used for seven cycles without showing any significant loss in performance. [ABSTRACT FROM AUTHOR]