Recent Submissions

  • Cu(II)-Catalyzed, Site Selective Sulfoximination to Indole and Indolines via Dual C–H/N–H Activation

    Kumar, Mohit; Rastogi, Anushka; Raziullah; Ahmad, Ashfaq; Gangwar, Manoj Kumar; Koley, Dipankar (Organic Letters, American Chemical Society (ACS), 2022-11-29) [Article]
    A copper-catalyzed protocol furnishing N-arylated sulfoximines has been developed via dual N-H/C-H activation. Arylalkyl- and less reactive diarylsulfoximines were efficiently coupled with privileged scaffolds like indolines, indoles, and N-Ar-7-azaindoles. Sulfoximines based on medicinally relevant scaffolds (phenothiazine, dibenzothiophene, thioxanthenone) were also well tolerated. Detailed mechanistic studies indicate that the deprotometalation and protodemetalation step is the reversible step.
  • Identification of distinctive structural and optoelectronic properties of Bi2O3 polymorphs controlled by tantalum addition

    Saito, Taro; Ahmad, Rafia; Kishimoto, Fuminao; Higashi, Tomohiro; Katayama, Masao; Cavallo, Luigi; Takanabe, Kazuhiro (Journal of Materials Chemistry C, Royal Society of Chemistry (RSC), 2022-11-25) [Article]
    Diverse crystal phases of bismuth (Bi) oxides induced by the addition of different amounts of tantalum (Ta) were synthesized. Their optoelectronic and redox properties were quantitatively investigated using combined experimental and computational approaches. Synthesis conditions that transform α-Bi2O3 into β-Bi2O3 and δ-Bi2O3 in terms of the Ta quantity, as well as synthesis temperatures, are identified and demonstrated. The phase transition behavior and crystal structures were characterized by in situ high temperature X-ray diffraction (XRD), thermogravimetry–differential thermal analysis (TG/DTA), X-ray absorption near edge structures (XANES), and extended X-ray absorption fine structures (EXAFS). Density functional theory calculations employing the HSE exchange–correlation functional with spin–orbit coupling were used to quantitatively simulate the optoelectronic properties and band structures of β-Bi2O3 and δ-Bi2O3. Along with the absorption coefficient and density of states, effective masses and dielectric constants were elucidated. The characterization study confirmed the distortion of Ta–O bonds in the Ta-supplemented β-Bi2O3 and the substitutional positions of the Bi and Ta atoms in the δ-Bi2O3 and Bi3TaO7 compounds. The reducibility of these oxides was strongly influenced by the crystal phase confirmed by temperature-programmed reduction (TPR) analysis. These findings can be used as a bismuth oxides' benchmark for optoelectronic applications as well as thermal catalysis as the redox active center or the support.
  • Incorporating Pd into Cu-Coordinated Metal-Organic Frameworks to Promote N2 Electrochemical Reduction into Ammonia

    Huang, Hao; Liu, Qiaoxi; Cheng, Qingpeng; Zhang, Maolin; Liu, Jialei (ChemCatChem, Wiley, 2022-11-24) [Article]
    Fixation nitrogen using renewable energy has attracted much attention recently. However, the performance is limited by the competing hydrogen evolution reaction (HER) and the difficulty in activating N2. Here, an attractive strategy was proposed to enhance the electrochemical nitrogen reduction reaction (NRR) activity by introducing Pd into the HKUST-1 framework. After thermal treatment, the obtained Pd/HKUST-1 (250 °C) catalyst exhibited an ammonia production rate of 42.0 mg/gcat ⋅ h at −0.4 V vs. RHE with Faradaic efficiency of 4.6 %. The ammonia production reached as high as 415 mg/gcat in a 10-hours stability test. With the assistance of density functional theory (DFT) calculations, the incorporated Pd was revealed to have the unique property to react with adsorbed H (Had) atom from HER and form α-PdH species. Compared with other metals such as Ag, Au, and Pt, the in situ formed α-PdH species could reduce the energy barrier of the rate-limiting *N2H step, resulting in an enhanced NRR activity.
  • Tuning the Properties of Ester-Based Degradable Polymers by Inserting Epoxides into Poly(ϵ-caprolactone)

    Hu, Shuangyan; Liu, Lijun; Li, Heng; Pahovnik, David; Hadjichristidis, Nikos; Zhou, Xuechang; Zhao, Junpeng (Chemistry – An Asian Journal, Wiley, 2022-11-24) [Article]
    A series of ester-ether copolymers were obtained via the reaction between α,ω-dihydroxyl poly(ϵ-caprolactone) (PCL) and ethylene oxide (EO) or monosubstituted epoxides catalyzed by strong phosphazene bases. The two types of monomeric units were distributed in highly random manners due to the concurrence of epoxide ring-opening and fast transesterification reactions. The substituent of epoxide showed an interesting bidirectional effect on the enzymatic degradability of the copolymer. Compared with PCL, copolymers derived from EO exhibited enhanced hydrophilicity and decreased crystallinity which then resulted in higher degradability. For the copolymers derived from propylene oxide and 1,2-butylene oxide, the hydrophobic alkyl pendant groups also allowed lower crystallinity of the copolymers thus higher degradation rates. However, further enlarging the pendant groups by using styrene oxide or 2-ethylhexyl glycidyl ether caused a decrease in the degradation rate, which might be ascribed to the higher bulkiness hindering the contact of ester groups with lipase.
  • Poly(amino ester)s as an emerging synthetic biodegradable polymer platform: Recent developments and future trends

    Wang, Xin; Zhang, Zhengbiao; Hadjichristidis, Nikos (Progress in Polymer Science, Elsevier BV, 2022-11-24) [Article]
    Poly(amino ester)s (PAEs) refer to a class of synthetic polymers characterized by repeating units in the backbone having tertiary amines and ester bonds, and bringing together the inherent biodegradability of polyesters and the rich tunable functionalities provided by tertiary amines. The presence of tertiary amines allows the introduction of various pendant groups, leading to diverse PAE material and properties, such as biodegradability, biocompatibility, water-solubility, stimulus-responsiveness (pH or temperature), etc. To date, PAEs are evolving into a new class of biodegradable polymer materials independent of aliphatic polyesters and have been widely used in various biomedical fields, such as gene delivery, drug delivery, bioimaging agents, etc. In addition, a new family of PAEs, namely N-acylated PAEs, with the same pendant carbonyl groups as poly(2-oxazoline)s, is expected to develop into new biopolymer platforms similar to polypeptoids and polyoxazolines. This review comprehensively summarizes the synthesis methods of PAEs, including polycondensation (PCD), Michael addition polymerization (MAP), spontaneous zwitterionic copolymerization (SZWIP), and ring-opening polymerization (ROP).
  • Electrolyte Additive-Controlled Interfacial Models Enabling Stable Antimony Anodes for Lithium-Ion Batteries

    Cai, Tao; Sun, Qujiang; Cao, Zhen; Ma, Zheng; Wahyudi, Wandi; Cavallo, Luigi; Li, Qian; Ming, Jun (The Journal of Physical Chemistry C, American Chemical Society (ACS), 2022-11-23) [Article]
    Most electrolyte additives can improve lithium-ion batteries’ performance by forming a solid electrolyte interphase (SEI) layer on the electrode surface. However, the influences of such additives on the lithium-ion (Li+) solvation structure, particularly on the Li+ desolvation process and its relationship with the attained electrode performance, are mostly overlooked. Herein, we designed a novel ether-based electrolyte to stabilize the alloying anode (e.g., Sb, antimony) by introducing LiNO3 as an additive, where a new interfacial model was constructed to show the additive effect on the kinetic and thermodynamic properties of Li+–solvent–anion complex in the electrolyte. We find that the NO3– anion can weaken the Li+–solvent interaction, promote the Li+ desolvation, particularly mitigate electrolyte decomposition by tuning the location of the Li+–solvent–anion complex on the electrode surface, and then improve electrolyte stability. This is the first time to show that the LiNO3 additive can contribute to a far distance of the Li+–solvent–anion complex from the Sb anode surface rather than the role of forming SEI. Eventually, an extremely high capacity of 664 mAh g–1, extraordinary rate capability over 5C, and good cycle performance over hundreds of cycles were obtained. This work provides new insight into understanding the role of additives more comprehensively and offers guidance in designing electrolytes for stable lithium-ion batteries using alloying anodes.
  • Occurrence and stability of anion–π interactions between phosphate and nucleobases in functional RNA molecules

    Chawla, Mohit; Kalra, Kanav; Cao, Zhen; Cavallo, Luigi; Oliva, Romina (Nucleic Acids Research, Oxford University Press (OUP), 2022-11-23) [Article]
    We present a systematic structural and energetic characterization of phosphate(OP)–nucleobase anion…π stacking interactions in RNAs. We observed OP–nucleobase stacking contacts in a variety of structural motifs other than regular helices and spanning broadly diverse sequence distances. Apart from the stacking between a phosphate and a guanine or a uracil two-residue upstream in specific U-turns, such interactions in RNA have been scarcely characterized to date. Our QM calculations showed an energy minimum at a distance between the OP atom and the nucleobase plane centroid slightly below 3 Å for all the nucleobases. By sliding the OP atom over the nucleobase plane we localized the optimal mutual positioning of the stacked moieties, corresponding to an energy minimum below -6 kcal•mol−1, for all the nucleobases, consistently with the projections of the OP atoms over the different π-rings we observed in experimental occurrences. We also found that the strength of the interaction clearly correlates with its electrostatic component, pointing to it as the most relevant contribution. Finally, as OP–uracil and OP–guanine interactions represent together 86% of the instances we detected, we also proved their stability under dynamic conditions in model systems simulated by state-of-the art DFT-MD calculations.
  • Non-linear high Tg polyimide-based membranes for separating CO2/CH4 gas mixtures

    Madzarevic, Zeljka P.; Seoane, Beatriz; Gascon, Jorge; Hegde, Maruti; Dingemans, Theo J. (Polymer, Elsevier BV, 2022-11-21) [Article]
    A novel series membranes based on non-linear all-aromatic polyimides (PIs) was investigated with the aim to understand how the PI backbone geometry and local electrostatics govern gas transport and the ability to separate CO2/CH4 mixtures. Non-linear 3-ring aromatic diamines, with exocyclic bond angles varying between 120 and 134°, enable the design of high Tg (>276 °C) PIs. A polar 1,3,4-oxadiazole diamine (ODD) (μ = 3D) monomer and a non-polar m-terphenyl diamine (TPD) reference monomer were synthesized and coupled with 3 dianhydrides, i.e. ODPA, ODDA, and 6FDA. In 6FDA-based membranes CO2 permeabilities (PCO2) are the highest of the series. The 6FDA-ODD membrane shows excellent membrane performance with high PCO2 values at all feed pressures. Up to 12 bar (6 bar CO2) none of the membranes reached their plasticization pressure. The non-linear backbone geometry promotes CO2 permeability, whereas the presence of an electrostatic dipole moment associated with the 1,3,4-oxadiazole heterocycle governs CO2/CH4 separation selectivity.
  • Basic Alkylamine Functionalized PAF-1 Hybrid Membrane with High Compatibility for Superior CO2 Separation from Flue Gas

    Zhang, Panpan; Zhang, Chi; Wang, Lei; Dong, Junchao; Gai, Dongxu; Wang, Wenjian; Nguyen, Thien Si; Yavuz, Cafer Tayyar; Zou, Xiaoqin; Zhu, Guangshan (Advanced Functional Materials, Wiley, 2022-11-20) [Article]
    Functionalized porous aromatic frameworks (PAFs) are excellent candidate materials for hybrid membrane fabrication. However, tailoring PAFs for membrane CO2 separation with desirable performance is still a challenge. Here, facile fabrication of functional hybrid alkylamine-modified PAF-1 containing membranes with high compatibility for efficient CO2/N2 separation is reported. The methylamino groups are installed on PAF-1 resulting in PAF-1-CH2NH2 that has a high surface area of over 1400 m2 g–1 and unique CO2 adsorption with CO2/N2 thermodynamic selectivity of over 1000. Amidation reaction is developed for PAF-1-CH2NH2 cross linking with cPIM-1 (carboxylic polymer of intrinsic microporosity), giving a homogenous compatible membrane of PAF-1-CH2NH2—cPIM-1 with outstanding CO2 permeability (≈10790 Barrer) and high CO2/N2 permselectivity (≈43). This membrane outperforms the counterparts derived from parent PAF-1 and phenylamine PAF-1 and possesses superior performance to other relevant membranes for CO2/N2 separation. Such a membrane can selectively and stably separate CO2 from N2 in a simulated flue gas mixture, demonstrating its huge potential in carbon capture.
  • MXene conversion to V2S3 heterostructure in CS2 ambient: A novel approach for sodium-ion battery anodes

    Huang, Gang; Yin, Jun; Zou, Guodong; Bayhan, Zahra; zhao, Wenli; Ming, Fangwang; Xu, Xiangming; Liang, Hanfeng; Mohammed, Omar F.; Alshareef, Husam N. (Elsevier BV, 2022-11-19) [Article]
    The abundant and wide distribution of sodium makes sodium-ion batteries (SIBs) one of the most promising battery technologies to supplement the current lithium-ion batteries in large-scale energy storage. However, the available anode materials are still far from satisfactory to enable the high-performance operation of SIBs. Here, a V2S3@C@V2S3 heterostructure anode is developed by one-step in-situ conversion of V2CTx MXene in CS2 ambient. The resultant electrode has abundant heterointerfaces and controllable V2S3 crystallinity and size. In this unique design, the carbon interlayer in the anode behaves like a flexible conductive support and an anchoring network. The ultrathin V2S3 nanosheets and the V2S3–C heterointerfaces enhance the Na+ adsorption and migration abilities, thus simultaneously mitigating the low conductivity, structural degradation, and sluggish kinetics of V2S3. As a result, this V2S3@C@V2S3 anode achieves a highly reversible capacity (628 mAh/g at 0.1 A/g), excellent rate performance (477 mAh/g at 10A/g), and impressive cycling stability (2000 cycles at 20 A/g, record-high value). This performance is far better than the parent MXene phase. Considering the rich compositional diversity of MXene, the in-situ conversion strategy developed here can be extended to construct a wide range of high-performance electrode materials for advanced batteries.
  • Cyclic Topologies in Linear α,ω-Dihydroxy Polyisoprenes by Dielectric Spectroscopy

    Pipertzis, Achilleas; Ntetsikas, Konstantinos; Hadjichristidis, Nikos; Floudas, George (Macromolecules, American Chemical Society (ACS), 2022-11-18) [Article]
    A series of mono- and di-functionalized polyisoprenes (PIs) bearing hydroxyl (OH−) end-group(s) with different molar masses ranging from 2 to 30 kg mol–1 were synthesized and studied by a combination of temperature- and pressure-dependent dielectric spectroscopy and rheology. In the di-functionalized PIs, the −OH end-group interactions result in a mixture of linear and cyclic configurations (up to 45% cyclic configurations for the lower molar masses). The formation of cyclic topologies due to increased H-bonding interactions restricted the backbone mobility and increased the glass temperature, Tg, especially for the lower molar masses. Moreover, an additional process (termed α*) was evidenced in the dielectric spectroscopy in the range between the segmental process and the global chain relaxation. It followed a Vogel–Fulcher–Tammann temperature dependence, freezing at a temperature in the vicinity of the liquid-to-glass temperature, being independent of molar mass. Its molecular origin was identified by employing the pressure sensitivity of the characteristic relaxation times and the pressure dependence of Tg. It reflects the relaxation of segments in the vicinity of the H-bonded groups. Overall, this study provided information on the impact of weakly associating polar end-groups (hydroxyl) on the molecular dynamics of type-A polymers. Furthermore, it suggested promising routes for designing polymers with a higher concentration (>50%) of cyclic topologies, for example, by employing (i) short chains with (ii) strongly associating end groups (stronger than the hydroxyl end-groups).
  • Influence of the complete basis set approximation, tight weighted-core, and diffuse functions on the DLPNO-CCSD ( T1 ) atomization energies of neutral H,C,O-compounds

    Minenkov, Yury; Cavallo, Luigi; Peterson, Kirk A. (Journal of Computational Chemistry, Wiley, 2022-11-18) [Article]
    The impact of complete basis set extrapolation schemes (CBS), diffuse functions, and tight weighted-core functions on enthalpies of formation predicted via the DLPNO-CCSD(T1) reduced Feller-Peterson-Dixon approach has been examined for neutral H,C,O-compounds. All tested three-point (TZ/QZ/5Z) extrapolation schemes result in mean unsigned deviation (MUD) below 2 kJ mol−1 relative to the experiment. The two-point QZ/5Z and TZ/QZ CBS (Formula presented.) extrapolation schemes are inferior to their inverse power counterpart ((Formula presented.)) by 1.3 and 4.3 kJ mol−1. The CBS extrapolated frozen core atomization energies are insensitive (within 1 kJ mol−1) to augmentation of the basis set with tight weighted core functions. The core-valence correlation effects converge already at triple-ζ, although double-ζ/triple-ζ CBS extrapolation performs better and is recommended. The effect of diffuse function augmentation converges slowly, and cannot be reproduced with double- ζ or triple- ζ calculations as these are plagued with basis set superposition and incompleteness errors.
  • Unveiling Chemically Robust Bimetallic Squarate-Based Metal–Organic Frameworks for Electrocatalytic Oxygen Evolution Reaction

    Kandambeth, Sharath; Kale, Vinayak Swamirao; Fan, Dong; Bau, Jeremy; Bhatt, Prashant; Zhou, Sheng; Shkurenko, Aleksander; Rueping, Magnus; Maurin, Guillaume; Shekhah, Osama; Eddaoudi, Mohamed (Advanced Energy Materials, Wiley, 2022-11-18) [Article]
    Here, this work reports an innovative strategy for the synthesis of chemically robust metal–organic frameworks (MOFs), and applies them as catalysts for the electrocatalytic oxygen evolution reaction (OER). A bimetallic squarate-based MOF (Sq-MOF) with a zbr topology serves as an excellent platform for electrocatalytic OER owing to its open porous structure, high affinity toward water, and presence of catalytically active 1D metal hydroxide strips. By regulating the Ni2+ content in a bimetallic squarate MOF system, the electrochemical structural stability toward OER can be improved. The screening of various metal ratios demonstrates that Ni3Fe1 and Ni2Fe1 Sq-zbr-MOFs show the best performance for electrocatalytic OER in terms of catalytic activity and structural stability. Ni2Fe1 Sq-zbr-MOF shows a low overpotential of 230 mV (at 10 mA cm−2) and a small Tafel slope of 37.7 mV dec−1, with an excellent long-term electrochemical stability for the OER. Remarkably, these overpotential values of Ni2Fe1 Sq-zbr-MOF are comparable with those of the best-performing layered double hydroxide (LDH) systems and outperforms the commercially available noble-metal-based RuO2 catalyst for OER under identical operational conditions.
  • Toward Reduced CO2 Emissions from Vehicles: Onboard Capture and Storage System Using Metal-Organic Frameworks

    Pezzella, Giuseppe; Bhatt, Prashant; Alhaji, Abdulhadi; Ramirez, Adrian; Grande, Carlos A.; Gascon, Jorge; Eddaoudi, Mohamed; Sarathy, Mani (Research Square Platform LLC, 2022-11-17) [Preprint]
    The transportation sector is among the largest contributors to carbon dioxide (CO2) emissions and demands immediate action. Although electrification is a promising technology to decarbonize light-duty vehicles, it has limited potential when applied to heavy trucks due to their longer travel distances and weight constraints. Hence, possible mitigation pathways must be identified to lower trucks’ carbon footprint. In this work, we propose an onboard post-combustion capture and storage system on heavy-duty freight vehicles using two state-of-the-art metal-organic frameworks (MOFs) with high CO2 selectivity and high-storage-capacity, respectively. We selected KAUST-7 as the capturing material because of its high stability and selectivity toward CO2 even in humid conditions; while Al-soc-MOF-1 as a CO2 storing material for its high gravimetric and volumetric CO2 uptake between 10 and 50 bar. Our solution aimed to reduce heavy-duty vehicle CO2 emissions by at least 50% and achieve above 95% CO2 purity at the storage point. First, we measured and modeled KAUST-7’s thermodynamic and kinetic properties, then we simulated and optimized the process conditions for the carbon capture system in response to dynamic engine behavior. Additionally, we minimized the capture and storage mass, offering as result innovative methods to mitigate carbon emissions in the heavy-duty freight industry.
  • CO2 catch and release under direct sunlight

    Nguyen, Thien Si; Yavuz, Cafer Tayyar (Joule, Elsevier BV, 2022-11-16) [Article]
    Temperature swing adsorption- or absorption-based CO2 capture requires substantial energy for regeneration and cooling purposes. Therefore, a cheap heat source and a passive cooling practice would dramatically reduce the energy cost. In the current issue of Cell Reports Physical Science, the Sun group presents their fabricated device that can alternate contact with sunlight to utilize solar energy for desorption and facilitate natural cooling for adsorption. This reduces the energy demand significantly to less than 1 MJ/kg CO2.
  • Atypical Stability of Exsolved Ni-Fe Alloy Nanoparticles on Double Layered Perovskite for Co2 Dry Reforming of Methane

    Yao, Xueli; Cheng, Qingpeng; Attada, Yerrayya; Ould-Chikh, Samy; Ramirez, Adrian; Bai, Xueqin; Mohamed, Hend Omar; Li, Guanxing; Shterk, Genrikh; Zheng, Lirong; Gascon, Jorge; Han, Yu; Bakr, Osman; Castaño, Pedro (Elsevier BV, 2022-11-14) [Preprint]
    Dry reforming of methane simultaneously achieves several sustainability goals: valorizing methane-activating carbon dioxide while producing syngas. The catalyst has an enormous influence on the process viability by controlling activity, selectivity, and stability. A catalyst with uniform-sized Ni-Fe alloy nanoparticles anchored into double-layered perovskite is assembled via a facile one-step reduction strategy. Our method attains more exsolved Ni nanoparticles (94%) than the common conditions. The exsolved Ni0.15Fe0.05 catalyst shows exceptional stability in 260 h tests at 800°C, with one of the slowest coke formation rates compared with the state-of-the-art catalysts. Besides, no deactivation was observed during 40 h operation at more demanding and coking conditions (14 bar) where this process is more likely to operate industrially. Via experimental characterizations and computational calculations, the stability of the robust exsolved Ni-Fe catalyst is demonstrated by its unique balance of adsorbed species, which inhibits coking.
  • Nitrogen Reduction to Ammonia by a Phosphorus-Nitrogen PN3PMo(V) Nitride Complex: Significant Enhancement via Ligand Post-Modification

    Han, Delong; Chakraborty, Priyanka; Huang, Mei-Hui; Yang, Li; Huang, Hao; Goncalves, Theo; Emwas, Abdul-Hamid M.; Lai, Zhiping; He, Jr-Hau; Shkurenko, Aleksander; Eddaoudi, Mohamed; Huang, Kuo-Wei (CCS Chemistry, Chinese Chemical Society, 2022-11-11) [Article]
    Efforts to develop organometallic complexes for catalytic nitrogen reduction have seen significant progress in recent years. However, the strategies for improving the activity of the homogenous catalysts have been mainly focused on alternating ligands and metals so far. Herein, we report that the activity and stability of a PN3P-Mo pincer complex ( 2) toward dinitrogen (N2) reduction were greatly enhanced through the post-modification of the PN3P pincer framework of its parent complex ( 1). A high ratio of NH3/Mo (3525) was achieved in the presence of SmI2 as a reductant. In sharp contrast, 1 only afforded an NH3/Mo ratio of 21. Moreover, since supported by the anionic pincer ligand, 2 furnished a high oxidation state Mo(V) nitride complex as a plausible key intermediate in the catalytic process via N2-cleavage, suggesting a catalytic cycle that may involve different oxidation states (II/V) from those with 10-π electron configuration in the literature.
  • Progress of Heterogeneous Iridium-Based Water Oxidation Catalysts.

    Gao, Jiajian; Liu, Yan; Liu, Bin; Huang, Kuo-Wei (ACS nano, American Chemical Society (ACS), 2022-11-10) [Article]
    The water oxidation reaction (or oxygen evolution reaction, OER) plays a critical role in green hydrogen production via water splitting, electrochemical CO2 reduction, and nitrogen fixation. The four-electron and four-proton transfer OER process involves multiple reaction intermediates and elementary steps that lead to sluggish kinetics; therefore, a high overpotential is necessary to drive the reaction. Among the different water-splitting electrolyzers, the proton exchange membrane type electrolyzer has greater advantages, but its anode catalysts are limited to iridium-based materials. The iridium catalyst has been extensively studied in recent years due to its balanced activity and stability for acidic OER, and many exciting signs of progress have been made. In this review, the surface and bulk Pourbaix diagrams of iridium species in an aqueous solution are introduced. The iridium-based catalysts, including metallic or oxides, amorphous or crystalline, single crystals, atomically dispersed or nanostructured, and iridium compounds for OER, are then elaborated. The latest progress of active sites, reaction intermediates, reaction kinetics, and elementary steps is summarized. Finally, future research directions regarding iridium catalysts for acidic OER are discussed.
  • Oxidative Coupling of Methane (OCM) over Strontium-doped Neodymium Oxide: Parametric Evaluations

    ALAHMADI, Faisal; Bavykina, Anastasiya; Poloneeva, Daria; Ramirez, Adrian; Schucker, Robert; Gascon, Jorge (AIChE Journal, Wiley, 2022-11-09) [Article]
    Since its discovery in 1982, oxidative coupling of methane (OCM) has been considered one of the most promising approaches for the on-purpose synthesis of ethylene. The development of more selective catalysts is essential to improve process economics. In this work, undoped neodymium oxide as well as neodymium oxide doped with high (20%) and low (2.5%) levels of strontium were tested in a high-throughput fashion covering a wide range of operating conditions. The catalysts were shown to be able to achieve greater than 18% C2+ yield. Space velocity was shown to play a significant role in C2+ selectivity. For a methane to oxygen feed ratio of 3.5, selectivity increased with increasing space velocity, reaching a maximum of 62% at a methane conversion of 30% at an optimal space velocity of ~250,000 mL/h/g. The difference in activity between the three samples was linked to the contribution of different oxygen centers.
  • Formic Acid Dehydrogenation via an Active Ruthenium Pincer Catalyst Immobilized on Tetra-Coordinated Aluminum Hydride Species Supported on Fibrous Silica Nanospheres

    Yaacoub, Layal; Dutta, Indranil; Werghi, Baraa; Chen, Benjamin W. J.; Zhang, Jia; Abou-Hamad, Edy; Ling Ang, Eleanor Pei; Pump, Eva; Sedjerari, Anissa Bendjeriou; Huang, Kuo-Wei; Basset, Jean-Marie (ACS Catalysis, American Chemical Society (ACS), 2022-11-08) [Article]
    The demand for harmless and efficient energy sources is remarkably expanding, particularly after the increased awareness of global warming, greenhouse gas emissions, immense fossil fuel consumption, and so forth. Formic acid is considered a potential candidate as an energy carrier for reversible hydrogen storage owing to its decomposition to hydrogen (H2) and carbon dioxide (CO2) in the presence of suitable catalysts. However, selective and efficient decomposition of formic acid using classical heterogeneous catalysis is still challenging because most heterogeneous catalysts which are known are ill defined. Herein, we report a promising heterogeneous approach toward formic acid dehydrogenation using a ruthenium PN3P pincer complex, [Ru–H(CO) (tBuPN3P)] (I), immobilized on a fibrous silica nanosphere, KCC-1, with a strong Lewis acid character [(≡Si–O–Si≡) (≡Si–O−)2Al–H]. The resulting heterogeneous catalyst, [Ru(H) (CO) (tBuPN3P)]@[(≡Si–O–Si≡) (≡Si–O−)2Al–H] (III), has been fully characterized by advanced solid-state characterization techniques. In this compound, Al is tetrahedrally coordinated. It is a single-site catalyst which exhibits good stability toward water, high pressures, and high temperatures as well as good activity in formic acid dehydrogenation. An excellent turnover number of 600,000 and a recyclability of up to 45 cycles are observed.

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