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Global warming has gotten worse recently as a result of significant CO 2 emissions, making the development of technologies to lower greenhouse gas emissions of CO 2 a necessity. Thermo-catalytic hydrogenation of CO 2 into methanol, methane, carbon monoxide and olefin is a promising technique to overcome this problem, as it not only uses CO 2 as feedstock but also yields valuable chemicals. Presently, most catalytic studies reported on the development of new catalysts to overcome the limitations of conventional catalysts. ZnO is one of the metal oxides that has been frequently utilized as a support or promoter catalyst in CO 2 hydrogenation for the production of high value-added chemicals. However, the preparation of ZnO influenced the morphology and structure design of the fabricated catalysts. Recently, the tremendous inverse catalyst design involving ZnO has also been reported. The involvement of ZnO in CO 2 hydrogenation is very important as it provides sufficient surface area for metal dispersion, oxygen vacancies for the generation of active sites, basic/acid properties for adsorption-desorption of molecules as well as stability for long-term usage in the reaction process. Therefore, in this review, ZnO-based catalysts used in CO 2 hydrogenation and strategies to design ZnO-based catalysts were highlighted. Then, the mechanism involving ZnO-based catalysts in CO 2 hydrogenation was summarized. Finally, challenges and the future of the ZnO-based catalysts are provided, emphasizing the great potential for the efficient synthesis of high value-added chemicals by CO 2 conversion. [Display omitted] • Zinc oxide-based catalysts for CO 2 hydrogenation are systematically reviewed. • Modification of ZnO morphology and interfaces enhanced the catalytic activity. • The roles of ZnO in CO 2 hydrogenation are emphasized. • The possible mechanism over modified ZnO-based catalysts are presented. [ABSTRACT FROM AUTHOR]

Catalytic transformation of light alkanes to aromatic compounds which are feedstocks to petrochemical industries is an important process. Here, a simple method of co-impregnation was employed to synthesize Zn-Cu/ZSM-5 for propane aromatization. Copper of varying loading 1–3 wt% was co-impregnated with zinc to improve zinc stability at the reaction condition. Catalyst physicochemical properties were analyzed using XRD, BET, N 2 -adsorption, FTIR, FTIR-Pyridine, SEM, TEM, H 2 -TPR and XPS. The XRD and FTIR characterization showed that the modified catalysts retained their crystallinity after metal impregnation with the XPS confirming the metal species having oxidation state of 2+. Hydrogen-TPR and XPS change in reduction temperature and binding energy spectra showed stronger intermetallic interaction respectively. Incorporation of Cu with Zn on ZSM-5 reduced Bronsted acidity from the FTIR-Pyridine while N 2 -adsorption isotherms verified the catalyst are microporous. The performance tests for propane aromatization over synthesized catalysts were carried out in a fixed bed reactor using GHSV of 1200 ml/g-h at 540 °C and atmospheric pressure. Co-impregnation of Zn with Cu improved the catalytic activity and sustained aromatic selectivity at an average of 85% for 12 h' time on stream as compared to HZSM-5 (10%) and Zn/ZSM-5 (50%). Product distribution showed reduced light hydrocarbon formation and increased aromatic compounds with high selectivity towards toluene, m and o-xylene among the aromatic product distribution. The best aromatic selectivity product distribution was recorded for 2 wt% Cu with Zn, thus a more stable catalyst developed. XPS and H 2 -TPR analysis showed that the synergistic interaction between the two metals (Cu and Zn) improved the performance of bimetallic Zn-Cu/ZSM-5 catalyst by promoting zinc dispersion and stability during reaction. [ABSTRACT FROM AUTHOR]

• Successful synthesis of La 0.8 Zn 0.2 MnO 3 perovskite nanocatalyst via a sol-gel method. • Study of the effects of preparation conditions of La 0.8 Zn 0.2 MnO 3 catalyst on BTX oxidation. • Study of the effect of input voltage on BTX removal in a hybrid plasma-catalyst reactor. • Benzene, toluene and xylene oxidation percent of 90.00, 89.86, and 88.64 %, respectively. In this study, La 0.8 Zn 0.2 MnO 3 nanocatalysts were synthesized using sol-gel method at different citric acid to metal nitrate (C/N) ratios and different calcination temperatures. The synthesized catalysts were used for oxidation of benzene, toluene, and xylene (BTX) in a catalytic-plasma hybrid reactor at different input voltages of 5, 7.5, 10, 12.5, and 15 kV. The synthesized catalysts were analyzed by XRD, FESEM, EDX, FTIR, BET, and TEM. XRD analysis confirmed the effect of calcination temperature on crystalline degree of LnMnO 3 phase in perovskite La 0.8 Zn 0.2 MnO 3 catalyst. TEM analysis also confirmed production of particles in nanometer range. Moreover, FTIR and BET analyses indicated that C/N ratio has a direct effect on the amount of metal oxide functional groups and surface area of the resultant catalyst, respectively. The reactor tests showed that the use of C/N= 0.5 and calcination temperature of 700°C in catalyst preparation resulted in the best performance in BTX oxidation. Increasing the voltage up to 15 kV had a good effect on the oxidation ability of the catalyst as well. In these conditions, the highest oxidation percentages of benzene, toluene and xylene were equal to 90.00, 89.86, and 88.64 %, respectively. [Display omitted] [ABSTRACT FROM AUTHOR]

5-Hydroxymethylfurfural (HMF) serves as a significant biomass platform molecule, and its selective conversion to produce furan-based chemicals is of great significance for biomass refining. Herein, a zinc-modified cobalt catalyst supported by nitrogen-carbon material (Zn 1 Co 3 /N-C) was prepared and showed an adjustable performance in the selective hydrogenation or hydrogenolysis of HMF to produce two important furan-based chemicals, 2,5-bis(hydroxymethyl)furan (BHMF) or 2,5-dimethylfuran (DMF). The catalyst's outstanding performance can be attributed to its ability to utilize a synergistic mechanism involving metal-acid interactions. This mechanism is achieved by introducing a second metal element (Zn), which in turn modifies the electronic structure of the initial metal surface and adjusts the acid content. By regulating the reaction temperature, the selectivity of 93.7% for BHMF or 93.5% for DMF were achieved with almost complete conversion of HMF. The results of catalyst characterization reveal that the Co metal sites and the ZnO acid sites play a key role in the hydrogenation of C O bonds and the hydrogenolysis of C-O bonds. This study unveiled the mechanism underlying the impact of both the acid quantity and the electronic structure of the metal surface on catalytic performance through the utilization of the zinc-modified catalyst's activity. [Display omitted] • Zn-Modified Co/N-C Catalysts were prepared using the nitrogen doped carbon derived from MOFs as the support. • The catalyst showed superior activity for selective hydrogenation or hydrogenolysis of HMF. • High selectivity of 93.7% for BHMF or 93.5% for DMF were achieved. • A synergistic mechanism involving metal-acid interactions was studied. [ABSTRACT FROM AUTHOR]

Effectively converting greenhouse gas CO 2 into value-added chemicals, without the need for cocatalysts or solvents, is a vital objective in order to attain carbon neutrality and promote sustainable development. However, achieving this goal continues to pose significant challenges. In this study, the in-situ formed octadentate N5O3 tripodal ligand (H 3 L) reacts with ZnBr 2 and ZnI 2 to produce two ionic-type zinc catalysts, [Zn 2 (L)] 2 [ZnBr 4 ]·4CH 3 OH (IZ-1) and [Zn 2 (L)]I·CH 3 OH (IZ-2), respectively. In the [Zn 2 (L)] subunit, the two Zn ions exhibit non-symmetry and are coordinated with the N5O3 ligand in a five- and six-coordinate mode, respectively. Due to the coexistence of Lewis acidic Zn sites and nucleophilic Br- ions, IZ-1 shows remarkable catalytic performance in the cycloaddition of CO 2 with epoxides. Under cocatalyst- and solvent-free conditions, it achieves an excellent yield of cyclic carbonates, reaching up to 99 %. The ionic-type zinc catalyst can be readily recovered and reused at least for five times without a noticeable loss in catalytic activity. Mechanistic investigation demonstrates that the improved activity of IZ-1 is attributed to the synergistic effect of Lewis acidic Zn centers and nucleophilic Br-. Moreover, the broad substrate scope of IZ-1 further highlights its versatility and applicability in the cycloaddition reaction. [Display omitted] • Two ionic-type zinc complexes were successfully synthesized. • Under cocatalyst- and solvent-free conditions, it achieves an excellent yield of cyclic carbonates, reaching up to 99 %. • The catalyst can be readily recovered and reused at least for five times without a noticeable loss in catalytic activity. • The coexistence of Lewis acidic Zn centers and nucleophilic Br- synergistically catalyse the cycloaddition of CO 2. [ABSTRACT FROM AUTHOR]

Nowadays, it is very challenging to develop a low-cost, highly active and stable bi-functional catalyst for accelerating oxygen reduction reaction (ORR) and oxygen evolution (OER) reaction during the charge and discharge process of zinc-air battery. Herein, we successfully design a novel bi-metal oxide hybrid catalyst (ZnCo2O4-CNT) by inserting Zn ions. Benefiting from the robust synergetic effects between porous ZnCo2O4 and CNTs, the high conductivity and the unique nanostructure, the ZnCo2O4-CNT shows lots of accessible active sites and improved reactants and electrons transfer. As expected, the hybrid shows higher ORR and OER performances with larger limited diffusion current density (5.72 mA cm-2) and lower OER over-potential (0.49 V) than Pt/C and other ZnCo2O4-CNT samples. In addition, rechargeable zinc-air battery assembled with the bi-functional catalyst exhibits a high power density of 249.4 mW cm-2, a strong discharge durability and charge-discharge stability of 240 cycles. Notably, the flexible zinc-air battery also shows good battery performances with high power density and good flexibility. Hence, exploiting efficient bi-functional catalytic materials with excellent ORR and OER performance and assembling flexible devices will improve the development of current zinc-air batteries battery industry. [ABSTRACT FROM AUTHOR]

Zinc-air batteries (ZABs) have been considered as promising next-generation batteries due to their natural abundance, flat discharge voltage and high theoretical specific energy density. However, the wide application of these ZABs is seriously hindered by the high cost and poor electrochemical stability of noble electrocatalysts. In this paper, we develop a facile method to prepare ultra-small iron-based nitride and nitrogen doped carbon nanotubes (Fe2N/N-CNTs) hybrid materials as bifunctional electrocatalysts for ZABs. In the presence of CNTs with large surface areas, ultra-small Fe2N nanoparticles with the diameter of around 5 nm are successfully prepared. The oxygen reduction reaction (ORR) activity of Fe2N/N-CNTs is comparable to the Pt/C, while the oxygen evolution reaction (OER) activity is much better than the Pt/C. At last, the home-made ZABs with Fe2N/N-CNTs have significant rechargeable activities and cyclic stability. [ABSTRACT FROM AUTHOR]

• Hierarchical Co x Zn 1-x Fe 2 O 4 @TiO 2 nanocomposites were successfully synthesized. • Strong interconnection was observed between maximum yield of CO and CH 4 products and Co/Zn ratio. • Selectivity towards CH 4 and CO 2 was varied by tuning the Co/Zn ratio. • Z-scheme mechanism was proven by detailed electrochemistry analyses. Photocatalytic conversion of CO 2 in the gas phase involving Z-scheme mechanism was studied in the presence of Co x Zn 1-x Fe 2 O 4 @TiO 2 (x = 1; 0.2; 0.4; 0.6; 0.8; 0) catalyst nanocomposites. The catalysts were obtained in a two-step approach, consisting of a co-precipitation reaction forming the magnetic Ferrite nanoparticles and a hydrolysis-condensation reaction of the Ti-source forming the titania anatase phase, followed by a calcination procedure. The structural characterization was done by X-ray diffraction, Raman and UV-DR spectroscopy, and physisorption, confirming the presence of both structures in the nanocomposites, with a band gap between 3 and 3.23 eV. In order to determine the CO 2 conversion, a photocatalytic gas phase fixed-bed batch reactor in tandem with a GC analyzer were used. The tests were done under UVC light irradiation and CO, CH 4 were identified as the main products during photoconversion of CO 2. All the samples showed higher conversions compared to the well-known reference material P25 (Degussa). The CO 2 conversion was observed to be directly proportional with the Zn/Co metal ratio in the Ferrite structure, achieving for ZnFe 2 O 4 @TiO 2 ∼50 μmol g cat. -1 h-1 CO and ∼30 μmol g cat. -1 h-1 CH 4. Moreover, for the ZnFe 2 O 4 @TiO 2 catalyst methanol (CH 3 OH) formation was observed, while no traces of methanol were detected for the samples containing Co. The electrochemistry analyses clarified the different heterojunctions formed between Ferrites and TiO 2. Mott-Schottky plots revealed the formation of a Z-scheme mechanism for ZnFe 2 O 4 @TiO 2 explaining the best conversion results. On the other hand, the lower activity of CoFe 2 O 4 @TiO 2 was attributed to the formation of a type I heterojunction system. [ABSTRACT FROM AUTHOR]

Novel porous MOF Zn(Py)(Atz) with excellent water stability and recyclability presented satisfactory catalytic performance for CO 2 conversion under mild conditions. • A novel Lewis acid-base bifunctional MOF Zn(Py)(Atz) with abundant micropores with BET surface area 764.5 m2/g and pore volume 0.32 cm3/g) was facilely fabricated by simple solvothermal method. • Zn(Py)(Atz) exhibited good CO 2 sorption capacity of 52.3 cm3/g at 273 K and efficient catalytic performance of 92.1% propylene carbonate yield and 98% selectivity for CO 2 coupling with various epoxides under mild conditions (60 °C 1.5 MPa), which is comparable or super to the reported Zn-based MOFs catalysts. • Zn(Py)(Atz) showed excellent stability in distilled water (>1 week) and acid/base aqueous solution (pH = 2–14 for 72 h), and maintained high catalytic activity under wet condition. A novel Zn-based three-dimensional framework Zn 2 (Py)(Atz) 2 ·DMF·2H 2 O (H 2 Py = 3,5-Pyridinedicarboxylic acid, Hatz = 3-Amino-1,2,4-triazole) abbreviated as Zn(Py)(Atz), with micropores and outstanding stability, was facilely fabricated by employing mixed ligands of nitro-rich unit amitrole and 3,5-dipicolinic acid. The Zn site acted as Lewis acid for epoxides activation, abundant micropores (BET surface area 764.5 m2/g, pore volume 0.32 cm3/g) and nitro-rich unit facilitated CO 2 sorption and its activation. The acid-base synergistic effects of Zn(Py)(Atz) MOF catalyst resulted in its promising potential in CO 2 chemical conversion. Satisfactorily, Zn(Py)(Atz) exhibited decent CO 2 sorption capacity (52.3 cm3/g at 273 K) and good performance of 92.1% propylene carbonate yield and 98% selectivity for the CO 2 cycloaddition to propylene oxide under mild conditions (60 °C 1.5 MPa), also high cyclic carbonates yields and selectivities were obtained over various epoxides. Moreover, PXRD analysis confirmed the excellent stability of Zn(Py)(Atz) in distilled water (>1 week) and acid/or base aqueous solution (pH = 2–14 for 72 h), which could meet the demand of industrial environment. Additionally, the Zn(Py)(Atz) catalyst was completely recycled for seven times with little decrease in product yield. The efficient, highly stable, easily recycle and solvent-free catalyst reported herein is potential material in CO 2 capture and utilization. [ABSTRACT FROM AUTHOR]

• A series of Carbonic Anhydrase mimics were synthesized as CO2 hydration catalysts for enhancing CO2 absorption into carbon capture solvents. • Ancillary chloride ligands and a hydrophobic binding pocket are shown to be key features for activity of the catalysts. • DFT simulations suggest that [ZnII(PSAAMP)Cl2] and [ZnII(PSAMEA)Cl2] are catalyzing the CO2 hydration analogous to CA enzyme. • [ZnII(PSAAMP)Cl2] and [ZnII(PSAMEA)Cl2] are stable in harsh thermal and oxidative conditions with projected lifetimes >1500 h. • [ZnII(PSAAMP)Cl2] and [ZnII(PSAMEA)Cl2] exhibit 2–5 times greater enhancement in mass transfer than previous catalysts. Anthropogenic greenhouse gas emissions, such as CO 2 from fossil fuel combustion, are a global environmental, health, and economic concern. Aqueous amine-based CO 2 capture processes offer a technologically mature and relevant approach to CO 2 sequestration, although cost reduction strategies are still necessary for widespread deployment. Inspired by the metalloenzyme carbonic anhydrase (CA), we report the design, synthesis, and activity testing of zinc(II) complexes [ZnII(PSAAMP)Cl 2 ] (1) and [ZnII(PSAMEA)Cl 2 ] (2) as CO 2 hydration catalysts in aqueous amine solutions. The novel multifunctional ligand environment includes features in the primary and secondary coordination spheres that result in enhanced CO 2 mass transfer in industrially relevant carbon capture solvents and stability towards harsh industrial process conditions. Complexes that lack these key features do not show enhanced CO 2 absorption. Density functional theory (DFT) calculations that assess the catalytic pathway demonstrate how 1 and 2 catalyze CO 2 hydration analogous to CA. These catalysts increase mass transfer by 20–55% in lab scale experiments, offering the potential to reduce the cost of amine-based CO 2 capture processes without significantly altering industrial-scale system design, making rapid deployment of this critical bridge technology a viable strategy to reduce global greenhouse gas emissions. [ABSTRACT FROM AUTHOR]

In this study, a novel zinc sodium molybdate/graphite phase carbon nitride (Na 1.8 Zn 2.1 Mo 3 O 12 /g-C 3 N 4) heterostructure was synthesized by wet impregnation. The photocatalyst was characterized in detail from different phase purity, crystal structure, morphology, microstructure, optical properties, and showed that the preparation was successful. The effects of the loading amount of Na 1.8 Zn 2.1 Mo 3 O 12 , the initial concentration of pollutants, the amount of catalyst and the pH value on the reaction system were also discussed. The results of photocatalytic study showed that the photocatalytic activity of the synthesized Na 1.8 Zn 2.1 Mo 3 O 12 /g-C 3 N 4 photocatalyst for tetracycline (TC) under visible light treatment was better than that of the pure g-C 3 N 4 and Na 1.8 Zn 2.1 Mo 3 O 12. The improved catalytic activity can be attributed to the formation of heterojunction between Na 1.8 Zn 2.1 Mo 3 O 12 and g-C 3 N 4 and the effective separation of photogenerated electron hole pairs. The capture tests confirmed that superoxide radical (·O 2 -) and photogenerated hole (h+) are the main active species involved in the photocatalytic reaction. Finally, the possible mechanism of the synergistic effect of g-C 3 N 4 and Na 1.8 Zn 2.1 Mo 3 O 12 to improve the photocatalytic performance was studied. • A novel visible light responsive Na 1.8 Zn 2.1 Mo 3 O 12 photocatalysts were fabricated by hydrothermal and calcination method. • The introduction of Na 1.8 Zn 2.1 Mo 3 O 12 optimized the separation rate of photogenerated electron hole pairs in g-C 3 N 4. • Na 1.8 Zn 2.1 Mo 3 O 12 /g-C 3 N 4 presented excellent photocatalysis and photochemical stability towards degradation of tetracycline. • The electron transfer mechanism and possible degradation mechanism between Na 1.8 Zn 2.1 Mo 3 O 12 and g-C 3 N 4 were discussed. [ABSTRACT FROM AUTHOR]

A novel, cost effective and magnetically separable nanocrystalline starch zinc catalyst was developed for the synthesis of α-alkylidene cyclic carbonates from propargylic alcohols and CO 2 at room temperature under solvent-free conditions. The synthesized nanocomposite along with triethylamine played excellent synergistic roles in activating both CO 2 and propargylic alcohols and afforded desired products in moderate to excellent yields. The salient features such as the use of renewable, inexpensive support matrix, facile separation of the catalyst by an external magnet, mild reaction conditions, excellent product yields and heterogeneous nature of the catalyst without any detectable leaching make the developed methodology promising for the synthesis of α-alkylidene cyclic carbonates. [ABSTRACT FROM AUTHOR]

A new catalyst system Ni(PPh 3 ) 2 (Naphthyl)Cl/PPh 3 /n-Bu 4 NBr/Zn was developed and the system showed high activity and selectivity for the coupling reaction of carbon dioxide (CO 2 ) and epoxides. The effects of reaction temperature, CO 2 pressure and different component of catalyst system have been investigated systematically. It was found that a 92.6% conversion of propylene oxide (PO), high selectivity (>99%) and turnover frequency (TOF) value (661 h −1 ) could be achieved within 5 h in the presence of Ni(PPh 3 ) 2 (Naphthyl)Cl/PPh 3 /n-Bu 4 NBr/Zn/PO (molar ratio = 1:2:4:20:3600) at a low pressure of CO 2 (3.0 MPa) and temperature (130 °C) without any organic solvents. Moreover, the conversion yield for epichlorohydrin and styrene oxide were alomost 100% with 100% selectivity at the same conditions. The catalyst was also proved to be applicable to other terminal epoxides. Besides, the influence of water on the catalytic activity within the range of H 2 O/PO (0–15 molar ratio) was elucidated, and a reaction mechanism focusing on the active Ni(0) center has been proposed, which plausibly explained the reaction result. [ABSTRACT FROM AUTHOR]

Amine-functionalized bimetallic zeolitic imidazolate framework-8 (Co/Zn-ZIF-A) with 3-amino-1,2,4-triazole (Atz) was synthesized by a post-synthetic modification and utilized as a heterogeneous catalyst for the synthesis of cyclic carbonates from CO 2 and epoxides. Different amine contents in Co/Zn-ZIF-A materials were controlled by adjusting the ligand exchange reaction time of the of 2-mIM with Atz. Co/Zn-ZIF-A-24 h with the highest amine contents (32% of Atz) achieved an excellent result of 99% conversion of epichlorohydrin with high selectivity of > 99% after 24 h without co-catalyst and solvent under mild conditions (80 oC, 1 bar CO 2). The enhanced catalytic activity is attributed to the acid-base synergistic effect by the combination of bimetallic systems consisting of Zn and Co as Lewis acid sites and the abundant Lewis bases sites of -NH 2 , -NH groups from Atz ligand. A kinetic study of the cycloaddition reaction over Co/Zn-ZIF-A-24 h confirmed an approximately first-order dependence on the epichlorohydrin concentration and CO 2 pressure with an activation energy of approximately 39.5 kJ mol-1. Co/Zn-ZIF-A-24 h catalyst showed good reusability with no obvious loss in catalytic activity during five recycling runs and its structural stability was also confirmed. A plausible reaction mechanism of Co/Zn-ZIF-A catalyst for CO 2 -epoxide cycloaddition was proposed. [Display omitted] • Amine-functionalized bimetallic Co/Zn-ZIFs (Co/Zn-ZIF-A) were synthesized by post-synthetic modification. • Co/Zn-ZIF-A was found to be catalytically efficient for CO 2 /epoxide coupling reaction under mild conditions. • Synergistic effect of amine groups and bimetallic systems on accelerating the epoxide ring-opening. • Co/Zn-ZIF-A demonstrates excellent catalytic activity without solvent and any co-catalyst. [ABSTRACT FROM AUTHOR]

Zinc bulk catalysts (Zn, ZnO and ZnCl 2 ) were used for the thermo-catalytic pyrolysis of EPSW and were found with high activity and selectivity of products. Thermo-catalytic pyrolysis was carried out using an efficient Pyrex batch reactor. Zn metal catalyst was found as the best catalyst amongst the zinc bulk catalysts for the cost effective pyrolysis of EPSW (expanded polystyrene waste). The yield of liquid products at 450 °C, 120 min heating time and 1:0.2 feed to catalyst ratio was 96.73 ± 0.12 wt.% with 2.47 wt.% toluene, 1.16 wt.% ethylbenzene, 47.96 wt.% styrene monomer and 1.90 wt.% α-methylstyrene. The components of liquid products were separated by fractional distillation and found with further thermal pyrolysis in addition to cyclization and recombination reactions. During the fractional distillation, much product variations were observed. High molecular weight aromatic hydrocarbons decreased with the associated increase of low molecular weight aromatic hydrocarbons, particularly toluene and ethylbenzene. [ABSTRACT FROM AUTHOR]

Novel hybridization of g-C 3 N 4 /Zn 0.28 Cd 0.72 S heterjunctions photocatalysts was successfully synthesized via the combination of chemisorptions and thermal post-treatment, wherein the g-C 3 N 4 serves as substrates to provide sites to anchor the Zn 0.28 Cd 0.72 S nanorods. These nanostructured g-C 3 N 4 /Zn 0.28 Cd 0.72 S composites were extensively characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), ultraviolet–visible diffuse reflection spectroscopy (UV–vis-DRS) and X-ray photoelectron spectrometer (XPS). The UV–vis-DRS results revealed that absorption spectral range of hybrid composites is a monotonous enhancement with the increasing Zn 0.28 Cd 0.72 S concentration in the visible light region. Interestingly, the catalytic performance of the g-C 3 N 4 /Zn 0.28 Cd 0.72 S is strongly dependent on the loading of Zn 0.28 Cd 0.72 S. The photocatalytic results demonstrate that 70 wt% g-C 3 N 4 /Zn 0.28 Cd 0.72 S hybrid photocatalyst exhibits the highest efficiency for the degradation of RhB and 4-ABA pollutants under visible light irradiation. And cycling photocatalytic tests for photocatalytic decomposition of RhB also indicate this photocatalyst is stable enough. The Fermi level ( E F ) and band position calculations reveal that g-C 3 N 4 and Zn 0.28 Cd 0.72 S are well-matched overlapping band structure, which may be in favour of enhanced separation rate of holes and electrons for reason of the development of heterogeneous interface. The interfacial charge transfer process was further verified in the photoreaction system of g-C 3 N 4 /Zn 0.28 Cd 0.72 S on the basis of VB-XPS and photoluminescence spectra (PL) analysis. [ABSTRACT FROM AUTHOR]

Abstract: The production of carbon nanotubes (CNTs) and pure hydrogen by the thermo catalytic decomposition of methane using a nano-size Ni-Cu-Zn/MCM-22 catalyst was investigated. The effect of Cu and Zn promoters was investigated by varying the amounts of Cu and Zn from 5 to 15wt% on a 50%Ni/MCM-22 catalyst prepared by wet impregnation. The performance of these catalysts was investigated in a fixed bed tubular reactor. The catalyst 50%Ni-10%Cu-10%Zn/MCM-22 resulted highest yield of hydrogen, and bamboo-shaped CNTs compared to other catalysts. The morphology of the carbon product strongly depended on reaction temperature, the amount of copper and zinc loading, flow rate and the partial pressure of methane. At higher reaction temperatures (>750°C) methane conversion and the yield of CNTs decreased due to sintering of the Ni particles. The experimental conditions for optimizing the carbon yield were also investigated and the most favorable conditions were observed at 750°C and at a methane partial pressure of 0.25atm. The aim of this study was to investigate the influence of reaction conditions on the morphology and formation of bamboo-shaped carbon filaments on a metal nanoparticle-based catalyst at moderate temperature. [Copyright &y& Elsevier]

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The article examines efforts to decarbonize the production of ammonia by using electrochemical synthesis to convert nitrogen gas to ammonia. It describes how a major waste stream could become a resource in a new process that turns nitrates into ammonia with the power of the sun. It mentions work of Meenesh Singh, a professor of chemical engineering at the University of Illinois at Chicago, in this field.

Zinc salts and SO 2 would cause Mn-Ce/AC catalyst poisoning, reducing the service life of the catalyst. In this study, the effects of Nb 2 O 5 on the tolerance of ZnCl 2 and SO 2 over Mn-Ce/AC catalyst were studied by the characterization results of BET, SEM, XRD, H 2 -TPR, NH 3 -TPD, TG and XPS. It indicated that doping Nb 2 O 5 could effectively enhance the SCR performance and N 2 selectivity of Zn-Mn-Ce/AC catalyst. Meanwhile, Nb 2 O 5 could significantly improve the SO 2 poisoning resistance of Zn-Mn-Ce/AC catalyst when sulfur dioxide was added into the reaction system. Nb 2 O 5 could react with SO 2 in a preferential way to restrain the sulfuration of manganese and cerium oxides on the catalyst. More importantly, Nb 2 O 5 reacted with SO 2 to form Nb sulfate and then formed a new acidic site on the Zn-Mn-Ce/AC catalyst surface, which promoted the adsorption of NH 3 and inhibited the adsorption of SO 2 , then restricted the reaction between NH 3 and SO 2 and hindered the formation of ammonium sulfate channels. [Display omitted] • Nb 2 O 5 could effectively improve the SCR activity of Zn-Mn-Ce/AC catalyst. • Nb 2 O 5 could effectively improve the N 2 selectivity of Zn-Mn-Ce/AC catalyst. • Nb 2 O 5 could improve anti-SO 2 poisoning performance of Zn-Mn-Ce/AC catalyst. • Nb 2 O 5 increased the redox ability, surface acidity, surface chemisorbed oxygen and Mn4+ content of Mn-Ce/AC catalyst. [ABSTRACT FROM AUTHOR]

Photocatalytic decolouration of dyes/pollutants using semiconducting materials has grabbed great attention in recent days. The current study focuses on a sol-gel method for preparing semiconducting materials such as TiO 2 (titanium oxide) and transition metal (Zn, Zr, Cu) doped TiO 2, which were characterized by X-ray Powder Diffraction (XRD), Scanning Electron Microscopy (SEM), UV–visible Diffuse Reflectance Spectroscopy (DRS) and UV–visible spectrophotometer, respectively. The photocatalytic behaviour of samples was tested with Methylene blue (MB) dye by observing the decolouration of the MB dye in aqueous solutions under visible light irradiation. The UV-DRS spectra showed that Zn doped TiO 2 demonstrated a better photocatalytic efficiency than TiO 2 and Zr, Cu doped TiO 2 catalysts. The effect of Zn doped TiO 2 has a lesser band gap would probably lead to enhance the MB dye degradation in aqueous solutions under visible light irradiation compared to TiO 2 and Zr, Cu doped TiO 2 catalysts. UV–vis spectrum varied with the irradiation time between 10 and 60 min and the concentration of MB decreased with the increasing irradiation time. UV–vis study revealed that the Zn (0.01) doped TiO 2 exhibited 99.64% MB decolouration as compared to 90.4% by pure TiO 2. The absorbance spectrum of Zn doped TiO 2 exhibited the lighter harvest in the visible light region, which facilitated more light energy for the utilization of the photocatalytic activity for the decoloration of MB. Zn doped TiO 2 catalyst exhibited a greater photocatalytic activity than pure TiO 2 and the other metal doped TiO 2 catalysts. [Display omitted] • The visible light assisted photodecoloration of Methylene Blue (MB) dye (Zr, Cu, Zn) doped TiO 2. • SEM shows excellent morphology and good surface structure of Zn doped TiO 2. • PXRD reveals that Zn doped TiO 2 and TiO 2 exhibits anatase and others exhibit rutile phase. • UV DRS confirmed that Zn doped TiO 2 has lesser a band gap than other catalytic systems. • The UV–vis study revealed that the Zn (0.01) doped TiO 2 exhibited 99.64% MB decolouration compared to 90.4% by pure TiO 2. [ABSTRACT FROM AUTHOR]

Chromium (VI) is a major water pollutant and suspected carcinogen with high persistence. Therefore, advance and fast processes based on low-cost and highly proficient nanomaterials are required for its elimination. Herein, nickel oxide-decorated zinc hexacyanocobaltate framework (NiO@ZnHCC) was synthesized by green method and subsequently, evaluated as photocatalyst for removal of Cr (VI) from synthetic wastewater. Various parameters were optimized in simulated water consisting of variable amounts of Cr(VI) (50–250 mg L−1) and catalyst dose (5–25 mg) at different pH (4–9)under sunlight exposure for 5 h. Highly crystalline nanocomposite (particle size range: 50–100 nm) consisting of NiO wrapped ZnHCC cubes piled together was confirmed by spectroscopic and microscopic analysis. At optimum catalytic dose (15 mg) and neutral pH, sharp decline in 50 mg L−1of Cr (VI) to Cr (III)was visually confirmed by colour change from orange to green. Highest removal (92%) of Cr (VI) by NiO@ZnHCCnanocomposite (Langmuir X m = 39 mg g−1) followed first order kinetics and indicated its greater efficiency as compared to individuals (NiO: 79% and ZnHCC: 86%). This might be due to improved surface area (78.9 m2 g−1), low band energy (2.1 eV) and semiconducting nature resulted from synergism of NiO (32.4 m2 g−1; 3.6 eV) and ZnHCC (38.9 m2 g−1; 2.3 eV). Moreover, NiO@ZnHCC reduced the half-life of Cr(VI) up to 1.1 h than that with ZnHCC (2.3 h) and NiO (3 h). Photo-catalytic reduction was probed using radical-scavenger analysis. Charge separation mechanism was supported by photoluminescence and UV reflectance studies. Overall, due to greater surface activity, stability, reusability up to ten-cycles and charge separation (e-+h+ pairs) led to promotion of huge free radicals, NiO@ZnHCC might be supposed as promising photocatalyst for industrial applications with bright future. ga1 • Green fabrication of Sunlight active reusable nanocomposite. • Quick reduction (92%) of Cr (VI) to Cr (III) by NiO@ZnHCC under Sunlight. • Optimization of concentration, pH, catalyst dose and source of irradiation. • Excellent reusability of photocatalyst up to 10th cycles. [ABSTRACT FROM AUTHOR]

The hydrogenation of CO 2 to methanol was performed over Ga 2 O 3 and ZrO 2 modified Cu-Zn based catalysts. The prepared catalysts were characterised via P-XRD, ICP-OES, BET, SEM-EDX, H 2 -TPR, CO 2 -TPD, H 2 -TPD and H 2 -chemisorption. The focus of this investigation was to assess the role of Ga 2 O 3 and ZrO 2 promoters on improving the methanol productivity over the Cu-Zn based catalysts. Emphasis was placed on the differences in CO 2 and H 2 adsorption capacity and strength due to the introduction of the modifiers, with a focus on the influence of these properties on methanol production. The ZrO 2 promoted catalyst delivered a higher methanol space-time yield (STY) in comparison to the Ga 2 O 3 promoted and unpromoted catalysts. The better catalytic performance of the ZrO 2 modified catalyst was partly attributed to an improvement of the reducibility. Furthermore, the CO 2 -TPD results showed that the ZrO 2 modified catalyst exhibited the highest CO 2 uptake and adsorption strength which contributed to its higher methanol yield. A correlation between the quantity of the spillover hydrogen and methanol yield was also shown to exist for the prepared catalysts. The results obtained from this study suggested that a strong interaction between CO 2 and the catalyst surface is crucial to avoid premature desorption of CO 2 or its intermediates, thus improving the efficiency of the catalyst. In contrast, an intermediate interaction of H 2 with the catalyst surface facilitates the hydrogen spill-over, which improves the methanol yield. ga1 • Cu-Zn catalysts promoted with Ga 2 O 3 and ZrO 2 , were prepared for the hydrogenation of CO 2 to methanol. • The ZrO 2 modified catalyst exhibited the highest CO 2 uptake and adsorption strength resulting in a higher methanol yield. • A correlation between the quantity of the spillover hydrogen and methanol yield was shown. [ABSTRACT FROM AUTHOR]

• Catalyzed cycloaddition of CO 2 over styrene oxide • More robust, Pyrrole-based Zn-N 4 SB were studied as Lewis acid catalysts • Good efficiency of Zn-N 4 SB along with tetrabutylammonium halides (NBu 4 X) • The optimized catalytic system can lead to TON up to 1400 and TOF up to 232 h−1. • Study supported by DFT calculations A series of Zn (II) complexes with nitrogen Schiff base ligands (NSB) has been synthesized from pyrrole carboxaldehyde. The prepared complexes were fully characterized. Single crystal X-ray diffraction analysis showed various coordination modes, as monomers or as helical dimers according to the number of available nitrogen atoms surrounding the zinc cation. The complex structure optimizations were carried out using the density functional theory (DFT) with ADF program and the dimerization energies and the temperature effect were examined. The Zn complexes were used as Lewis acids (LA) combined with tetrabutylammonium halides (N 4 BuX) as Lewis bases (LB), for the catalytic valorization of CO 2 into cyclic carbonates. A new momomeric Zn-NSB was chosen to study the influence of different reaction parameters (temperature, CO 2 pressure, LA/LB molar ratio, catalyst amount). Thus, optimized conditions afforded the solvent-free selective formation of styrene cyclic carbonate in good yields (up to 98 %) and allowed the reuse of this Zn-NSB/N 4 BuX catalytic system without any loss of activity. [ABSTRACT FROM AUTHOR]

• Tetrapyridino porphyrazinato zinc(II) as a catalyst for CO 2 insertion. • Cyclic carbonate production from epoxideds in H 2 O at low temperature. • No adding of onium salts as the co-catalyst. The highly active water soluble bifunctional catalyst of porphyrazinato zinc(II) ([Zn(2,3-tmtppa)](MeSO 4) 4) in which tmtppa stands for tetramethylated tetrapyridino porphyrazine was applied for cycloaddition reaction of CO 2 into epoxides to obtain cyclic carbonates. It seems that our catalyst can act as an efficient phase transfer agent because of the presence of tetra positive groups in its structure which increased catalyst solubility in water. Accordingly, the CO 2 fixation reaction was performed in water utilizing cheap, simple and commercially available potassium iodide co-catalyst instead of expensive quaternary onium salts (as co-catalyst) because of having the quaternized parts in the porphyrazine skeleton. The mentioned homogeneous catalytic system was adaptable to CO 2 insertion into aliphatic, aromatic and functional epoxides efficiently and selectively under mild reaction conditions. Furthermore, our catalyst system was easily recovered and reused in at least three cycles without any decrease of catalytic activity. [ABSTRACT FROM AUTHOR]

• The mechanism occurs by adsorption and dissociation of CO 2 into CO* and O*. • In situ transmission FTIR showed that CO was adsorbed onto the Cu+/0 sites. • The catalyst with the higher surfactant amount exhibited the highest CO 2 conversion In this study, we evaluated aspects of the CO 2 hydrogenation mechanism, correlating structure-activity relationships of Cu-ZnO-ZrO 2 catalysts prepared by one-pot surfactant-assisted co-precipitation with different surfactant ratios. Identifying the CO 2 hydrogenation pathway intermediates is key to controlling the reaction selectivity. Experimental evidence shows that the CO 2 is dissociating into CO* and O* onto the surface of the Cu-ZnO-ZrO 2 catalyst. The adsorption and dissociation of CO 2 were evidenced by a combination of in situ ambient-pressure X-ray Photoelectron Spectroscopy (AP-XPS) and Fourier Transform Infrared Spectroscopy (FTIR) with a transmission cell. AP-XPS showed that the catalysts are composed of a Cu2+, Zr3+, and Zr4+ mixture and two kinds of Zn2+ species. After the H 2 reduction process, only Cu2+ was reduced to Cu0. The Zn and Zr species were oxidized by the dissociated O* species. In situ transmission FTIR showed that CO was adsorbed onto the Cu+/0 sites. The catalyst with the higher surfactant molar ratio exhibited the highest CO 2 conversion close to the equilibrium conversion, as well as a good methanol formation rate. [ABSTRACT FROM AUTHOR]