Recent Submissions

  • Barcoding Amino Acids for Mutation Screening in Amyloid Beta Peptides

    Hoang, Phuong Mai; Khashab, Niveen M. (Small Methods, Wiley, 2019-10-04) [Article]
    Amino acid (AA) substitutions are directly correlated with specific pathologies such as Alzheimer's disease, making their rapid screening and detection critical to treatment and scientific study. A proof-of-concept implementation of the label-free and noninvasive Raman spectroscopy technique for the detection of AA substitutions in primary peptide fragments is demonstrated. By encoding the Raman “fingerprint” of individual AAs into binary formats called optical identification tags (OITs), a library of identifiers is created, which can then be used for detecting mutations. When the recorded Raman signal is enhanced by using surface-enhanced Raman scattering substrate, the mutation screening strategy can detect a single point missense mutation in an 11-AA peptide fragment of amyloid beta Aβ(25–35) and a frameshift mutation in a 42-AA fragment Aβ(1–42) down to picomolar concentrations. The combination of high sensitivity and simple operation makes the use of OITs a promising approach for high-throughput automated screening.
  • 3D Analysis of Ordered Porous Polymeric Particles using Complementary Electron Microscopy Methods

    Alvarez, Juan; Saudino, Giovanni; Musteata, Valentina-Elena; Madhavan, Poornima; Genovese, Alessandro; Behzad, Ali Reza; Sougrat, Rachid; Boi, Cristiana; Peinemann, Klaus-Viktor; Nunes, Suzana Pereira (Scientific Reports, Springer Science and Business Media LLC, 2019-09-27) [Article]
    Highly porous particles with internal triply periodic minimal surfaces were investigated for sorption of proteins. The visualization of the complex ordered morphology requires complementary advanced methods of electron microscopy for 3D imaging, instead of a simple 2D projection: transmission electron microscopy (TEM) tomography, slice-and-view focused ion beam (FIB) and serial block face (SBF) scanning electron microscopy (SEM). The capability of each method of 3D image reconstruction was demonstrated and their potential of application to other synthetic polymeric systems was discussed. TEM has high resolution for details even smaller than 1 nm, but the imaged volume is relatively restricted (2.5 μm)3. The samples are pre-sliced in an ultramicrotome. FIB and SBF are coupled to a SEM. The sample sectioning is done in situ, respectively by an ion beam or an ultramicrotome, SBF, a method so far mostly applied only to biological systems, was particularly highly informative to reproduce the ordered morphology of block copolymer particles with 32-54 nm nanopores and sampling volume (20 μm)3.
  • Gas separation performance and mechanical properties of thermally-rearranged polybenzoxazoles derived from an intrinsically microporous dihydroxyl-functionalized triptycene diamine-based polyimide

    Yerzhankyzy, Ainur; Ghanem, Bader; Wang, Yingge; Alaslai, Nasser Y.; Pinnau, Ingo (Journal of Membrane Science, Elsevier BV, 2019-09-25) [Article]
    An intrinsically microporous hydroxyl-functionalized polyimide (PIM-PI) made from 4,4′-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) and 2,6(7)-dihydroxy-3,7(6)-diaminotriptycene (DAT1-OH), was thermally converted to polybenzoxazole (PBO). The thermal rearrangement of the PIM-PI to PBO significantly increased the free volume, which was reflected by a boost in its microporosity as indicated by enhanced Brunauer-Emmett-Teller (BET) surface area from 167 to 405 m2 g−1. The increase in free volume noticeably improved the gas permeability but also resulted in reduced gas-pair selectivity. The fresh PBO membrane made by thermal treatment at 460 °C for 30 min (TRIP-TR-460-30) with a PBO conversion of 98% displayed a 20-fold higher CO2 permeability of 840 barrer than the initial value of 43 barrer for the 6FDA-DAT1-OH polyimide at the expense of ~ 60% decrease in pure-gas CO2/CH4 selectivity from 52 to 21. The TRIP-TR-460-30 PBO showed good performance for propylene/propane separation with pure-gas C3H6 permeability of 21 barrer and C3H6/C3H8 selectivity of 16 for a 28-days aged sample. When tested under mixed-gas conditions C3H6 permeability dropped to 12.8 barrer and C3H6/C3H8 selectivity of 8. TRIP-TR-460-30 PBO displayed mechanical properties comparable some rigid polyimides with tensile strength, Young's modulus and elongation at break of 58 MPa, 1.83 GPa and 4.3%, respectively.
  • Electrostatically-coupled graphene oxide nanocomposite cation exchange membrane

    Alabi, Adetunji; Cseri, Levente; Al Hajaj, Ahmed; Szekely, Gyorgy; Budd, Peter; Zou, Linda (Journal of Membrane Science, Elsevier BV, 2019-09-07) [Article]
    We report the preparation of an electrostatically-coupled graphene oxide nanocomposite cation exchange membrane (CEM) based on sulfonic group containing graphene oxide (SGO) (45 wt % loading) and polyvinylidene fluoride (PVDF), where the ion exchange groups were provided by the SGO additive. SGO was prepared via the mixing of graphene oxide (GO) with a mixture derived from 3,4-dihydroxy-L-phenylalanine (L-DOPA) and poly(sodium 4-styrenesulfonate) (PSS). A mold-casting technique was developed to fabricate the free-standing nanocomposite CEM. The presence of sulfonic groups in the nanocomposite was confirmed with FTIR spectroscopy. Energy dispersive spectroscopy analysis showed the SGO was distributed across the entire membrane matrix, with minimal aggregation. The resultant SGO/PVDF nanocomposite CEM membrane demonstrated high hydrophilicity and high water uptake, but low swelling ratio. Furthermore, evaluation of the electrochemical properties of the nanocomposite CEM showed favorable ion exchange capacity (0.63 ± 0.08 meq/g), permselectivity (0.95 ± 0.04), and area resistance (2.8 ± 0.2 Ω cm2). The nanocomposite CEM show good potential for use in electromembrane desalination applications.
  • Pillar[5]arene Stabilized Silver Nanoclusters: Immense Stability and Luminescence Enhancement Induced by Host-Guest Interactions.

    Muhammed, Madathumpady; Cruz, Laila; Emwas, Abdul-Hamid M.; El-Zohry, Ahmed; Moosa, Basem; Mohammed, Omar F.; Khashab, Niveen M. (Angewandte Chemie (International ed. in English), Wiley, 2019-08-29) [Article]
    Herein, we report the synthesis of a new class of functional silver nanoclusters (AgNCs) capped with pillar[5]arene (P5) based host ligands. These NCs are readily prepared via direct synthesis or ligand exchange synthesis and are stable at room temperature for over 4 months. The pillar[5]arene stabilized NCs (Ag29(LA-P5)12(TPP)2) endorse reversible host-guest interactions with neutral alkylamines and cationic quaternary ammonium guests. This results into the formation of spherical assemblies with unparalleled changes in their optical properties including an astonishing ≈2000-fold luminescence enhancement. This is the highest luminescence enhancement ratio reported so far for such atomically precise NCs. Our synthetic protocol paves the way for the preparation of a new generation of metal nanoclusters protected by macrocyclic ligands with molecular recognition and selectivity toward specific guests.
  • Quantum Dots Supply Bulk- and Surface-Passivation Agents for Efficient and Stable Perovskite Solar Cells

    Zheng, Xiaopeng; Troughton, Joel; Gasparini, Nicola; Lin, Yuanbao; Wei, Mingyang; Hou, Yi; Liu, Jiakai; Song, Kepeng; Chen, Zhaolai; Yang, Chen; Turedi, Bekir; Alsalloum, Abdullah; Pan, Jun; Chen, Jie; Zhumekenov, Ayan A.; Anthopoulos, Thomas D.; Han, Yu; Baran, Derya; Mohammed, Omar F.; Sargent, Edward H.; Bakr, Osman (Joule, Cell Presssubs@cell.com, 2019-08-21) [Article]
    We report a facile processing strategy that utilizes perovskite quantum dots (QDs) to distribute elemental dopants uniformly across a MAPbI3 film and anchor ligands to the film's surface—reducing the film's trap-state density and rendering its surface hydrophobic. QD-treated MAPbI3 films yield solar cells with 21.5% power conversion efficiency (PCE) (versus 18.3% for non-QD-treated) and maintain 80% of their initial PCE under 1-sun continuous illumination for 500 h with improved thermal stability.
  • Performance and Stability Improvement of Layered NCM Lithium-Ion Batteries at High Voltage by a Microporous Al2O3 Sol–Gel Coating

    Wu, Yingqiang; Li, Mengliu; Wahyudi, Wandi; Sheng, Guan; Miao, Xiaohe; Anthopoulos, Thomas D.; Huang, Kuo-Wei; Li, Yangxing; Lai, Zhiping (ACS Omega, American Chemical Society (ACS), 2019-08-19) [Article]
    A simple and low-cost polymer-aided sol–gel method was developed to prepare γ-Al2O3 protective layers for LiNi0.6Co0.2Mn0.2O2 (NCM622) cathode materials. The selected polyvinyl alcohol polymer additive not only facilitates the formation of a uniform and thin γ-Al2O3 layer on the irregular and rough cathode particle surface to protect it from corrosion but also serves as a pore-forming agent to generate micropores in the film after sintering to allow fast transport of lithium ions, which guaranteed the excellent and stable battery performance at high working voltage. Detailed studies in the full battery mode showed that the leached corrosion species from the cathode had a more profound harmful effect to the graphite anode, which seemed to be the dominating factor that caused the battery performance decay.
  • Computationally Assisted Assessment of the Metal-Organic Framework/Polymer Compatibility in Composites Integrating a Rigid Polymer

    Tavares, Sergio Rodrigues; Ramsahye, Naseem Ahmed; Adil, Karim; Eddaoudi, Mohamed; Maurin, Guillaume; Semino, Rocio (Advanced Theory and Simulations, Wiley, 2019-08-17) [Article]
    Density functional theory (DFT) calculations and subsequent classical molecular dynamics (MD) simulations are combined to build and further characterize the interface structure of three binary metal-organic framework (MOF)/polymer composite materials made of ultra-small pore MOFs with distinct surface morphologies, namely, MIL-69, ftw-MOF-ABTC, and ftw-MOF-BPTC, and the 6-FDA-DAM polymer. It is found that the three composites exhibit percolated or independent microvoids of different degrees of interconnectivity, sizes, and positions at the MOF/polymer interface that contribute to decrease the polymer surface coverage, a signature of a relatively poor adhesion between the two components. The ftw-MOF-BPTC-based composite, however, shows a partial penetration of the polymer in the MOF first pore layer, hinting a slightly higher affinity between the MOF and the polymer. These results suggest that even when considering MOFs surfaces with drastically different morphologies, finding a highly compatible MOF/polymer pair for rigid polymers remains challenging.
  • Scalable Synthesis of Amphiphilic Copolymers for CO2- and Water-Selective Membranes: Effect of Copolymer Composition and Chain Length

    Akhtar, Faheem; Kumar, Mahendra; Vovusha, Hakkim; Shevate, Rahul; Villalobos, Luis Francisco; Schwingenschlögl, Udo; Peinemann, Klaus-Viktor (Macromolecules, American Chemical Society (ACS), 2019-08-13) [Article]
    Dehumidification is a critical energy-intensive and crucial process for several industries (e.g., air conditioning and gas dehydration). Polymeric membranes with high water vapor permeability and selectivity are needed to achieve an energy-efficient water vapor removal. Herein, we demonstrate high-performance water vapor transport membranes based on novel amphiphilic tercopolymers. A series of amphiphilic tercopolymers comprising polyacrylonitrile, poly(ethylene glycol) methyl ether methacrylate (PEGMA), and poly(N,N-dimethylamino ethyl methacrylate) (PDMAEMA) segments are synthesized via an economical and facile free radical polymerization. The water vapor permeability increases with the increase in PEGMA chain length and the content of PEGMA segments. The best performing membrane (i.e., PEGMA-9502) achieved a water vapor permeability of 174 kBarrer. By optimizing the content and chain length of the PEGMA segments, the membranes could be tuned for carbon capture applications. The optimized membranes tested for CO2 separation showed a high CO2 permeability of 47 Barrer along with CO2/N2 and CO2/CH4 selectivities of 67 and 23, respectively. This work presents a simple and economic amphiphilic tercopolymer for the fabrication of membranes with excellent gas and water vapor separation performance.
  • The Growth of Photoactive Porphyrin-Based MOF Thin Films Using the Liquid-Phase Epitaxy Approach and their Optoelectronic Properties.

    Ngongang Ndjawa, Guy Olivier; Tchalala, Mohamed R; Shekhah, Osama; Khan, Jafar Iqbal; Mansour, Ahmed E; Czaban-Jozwiak, Justyna; Weselinski, Lukasz Jan; Ait Ahsaine, Hassan; Amassian, Aram; Eddaoudi, Mohamed (Materials (Basel, Switzerland), MDPI AG, 2019-08-04) [Article]
    This study reports on the optoelectronic properties of porphyrin-based metal-organic framework (MOF) thin films fabricated by a facile liquid-phase epitaxy approach. This approach affords the growth of MOF thin films that are free of morphological imperfections, more suitable for optoelectronic applications. Chemical modifications such as the porphyrin ligand metallation have been found to preserve the morphology of the grown films making this approach particularly suitable for molecular alteration of MOF thin film optoelectronic properties without compromising its mesoscale morphology significantly. Particularly, the metallation of the ligand was found to be effective to tune the MOF bandgap. These porphyrin-based MOF thin films were shown to function effectively as donor layers in solar cells based on a Fullerene-C60 acceptor. The ability to fabricate MOF solar cells free of a liquid-phase acceptor greatly simplifies device fabrication and enables pairing of MOFs as light absorbers with a wide range of acceptors including non-fullerene acceptors.
  • Direct, Selective Production of Aromatic Alcohols from Ethanol Using a Tailored Bifunctional Cobalt-Hydroxyapatite Catalyst

    Wang, Qing Nan; Weng, Xue Fei; Zhou, Bai Chuan; Lv, Shao Pei; Miao, Shu; Zhang, Daliang; Han, Yu; Scott, Susannah L.; Schüth, Ferdi; Lu, An Hui (ACS Catalysis, American Chemical Societyservice@acs.org, 2019-08-02) [Article]
    Aromatic alcohols are essential components of many solvents, coatings, plasticizers, fine chemicals, and pharmaceuticals. Traditional manufacturing processes involving the oxidation of petroleum-derived aromatic hydrocarbons suffer from low selectivity due to facile overoxidation reactions which produce aromatic aldehydes, acids, and esters. Here we report a Co-containing hydroxyapatite (HAP) catalyst that converts ethanol directly to methylbenzyl alcohols (MB-OH, predominantly 2-MB-OH) at 325 °C. The dehydrogenation of ethanol to acetaldehyde, which is catalyzed by Co2+, has the highest reaction barrier. Acetaldehyde undergoes rapid, HAP-catalyzed condensation and forms the key intermediate, 2-butenal, which yields aromatic aldehydes through self-condensation and then MB-OH via hydrogenation. In the presence of Co2+, 2-butenal is selectively hydrogenated to 2-butenol. This reaction does not hinder aromatization because cross-coupling between 2-butenal and 2-butenol leads directly to MB-OH without passing through MBâ•O. Using these insights a dual-bed catalyst configuration was designed for use in a single reactor to improve the aromatic alcohol selectivity. Its successful use supports the proposed reaction mechanism.
  • Direct, Selective Production of Aromatic Alcohols from Ethanol Using a Tailored Bifunctional Cobalt-Hydroxyapatite Catalyst

    Wang, Qing Nan; Weng, Xue Fei; Zhou, Bai Chuan; Lv, Shao Pei; Miao, Shu; Zhang, Daliang; Han, Yu; Scott, Susannah L.; Schüth, Ferdi; Lu, An Hui (ACS Catalysis, American Chemical Societyservice@acs.org, 2019-08-02) [Article]
    Aromatic alcohols are essential components of many solvents, coatings, plasticizers, fine chemicals, and pharmaceuticals. Traditional manufacturing processes involving the oxidation of petroleum-derived aromatic hydrocarbons suffer from low selectivity due to facile overoxidation reactions which produce aromatic aldehydes, acids, and esters. Here we report a Co-containing hydroxyapatite (HAP) catalyst that converts ethanol directly to methylbenzyl alcohols (MB-OH, predominantly 2-MB-OH) at 325 °C. The dehydrogenation of ethanol to acetaldehyde, which is catalyzed by Co2+, has the highest reaction barrier. Acetaldehyde undergoes rapid, HAP-catalyzed condensation and forms the key intermediate, 2-butenal, which yields aromatic aldehydes through self-condensation and then MB-OH via hydrogenation. In the presence of Co2+, 2-butenal is selectively hydrogenated to 2-butenol. This reaction does not hinder aromatization because cross-coupling between 2-butenal and 2-butenol leads directly to MB-OH without passing through MBâ•O. Using these insights a dual-bed catalyst configuration was designed for use in a single reactor to improve the aromatic alcohol selectivity. Its successful use supports the proposed reaction mechanism.
  • Direct, Selective Production of Aromatic Alcohols from Ethanol Using a Tailored Bifunctional Cobalt-Hydroxyapatite Catalyst

    Wang, Qing Nan; Weng, Xue Fei; Zhou, Bai Chuan; Lv, Shao Pei; Miao, Shu; Zhang, Daliang; Han, Yu; Scott, Susannah L.; Schüth, Ferdi; Lu, An Hui (ACS Catalysis, American Chemical Societyservice@acs.org, 2019-08-02) [Article]
    Aromatic alcohols are essential components of many solvents, coatings, plasticizers, fine chemicals, and pharmaceuticals. Traditional manufacturing processes involving the oxidation of petroleum-derived aromatic hydrocarbons suffer from low selectivity due to facile overoxidation reactions which produce aromatic aldehydes, acids, and esters. Here we report a Co-containing hydroxyapatite (HAP) catalyst that converts ethanol directly to methylbenzyl alcohols (MB-OH, predominantly 2-MB-OH) at 325 °C. The dehydrogenation of ethanol to acetaldehyde, which is catalyzed by Co2+, has the highest reaction barrier. Acetaldehyde undergoes rapid, HAP-catalyzed condensation and forms the key intermediate, 2-butenal, which yields aromatic aldehydes through self-condensation and then MB-OH via hydrogenation. In the presence of Co2+, 2-butenal is selectively hydrogenated to 2-butenol. This reaction does not hinder aromatization because cross-coupling between 2-butenal and 2-butenol leads directly to MB-OH without passing through MBâ•O. Using these insights a dual-bed catalyst configuration was designed for use in a single reactor to improve the aromatic alcohol selectivity. Its successful use supports the proposed reaction mechanism.
  • Outstanding methane gravimetric working capacity of computationally designed rhr-MOFs

    Suetin, Mikhail; Peskov, Maxim; Schwingenschlögl, Udo (Microporous and Mesoporous Materials, Elsevier BV, 2019-07-29) [Article]
    A multi-scale approach is employed to design metal-organic frameworks (MOFs). The methane sorption properties are studied by grand canonical Monte Carlo simulations to reveal the structure-property relationship with respect to the methane total uptake and working capacity at different temperatures and pressures. We identify rhr-MOFs with outstanding gravimetric working capacity. For example, the BBB MOF (largest studied pore size) achieves a value of 60.7 wt% at 298 K and 5–65 bar.
  • Simultaneous production and functionalization of hexagonal boron nitride nanosheets by solvent-free mechanical exfoliation for superlubricant water-based lubricant additives

    An, Lulu; Yu, Yuanlie; Bai, Changning; Bai, Yongqing; Zhang, Bin; Gao, Kaixiong; Wang, Xinbo; Lai, Zhiping; Zhang, Junyan (npj 2D Materials and Applications, Nature Publishing GroupHoundmillsBasingstoke, HampshireRG21 6XS, 2019-07-26) [Article]
    Hexagonal boron nitride nanosheets (h-BNNSs), with a crystal lattice structure similar to graphene by over 98%, exhibit good lubrication properties as lubricant additives. However, the poor dispersibility in solvents has limited their wide practical applications as lubricant additives. In the present report, water dispersible Pebax functionalized h-BNNSs (Pebax-BNNSs) have been prepared through a one-step solvent-free mechanical exfoliation process which relies on a simple exfoliation of h-BN layers by shearing force in molten Pebax at 200 °C. In this process, Pebax molecules can synchronously react with the dangling bonds formed during the exfoliation process to achieve in situ functionalization of h-BNNSs. The reciprocating friction tests demonstrate that the as-obtained Pebax-BNNSs possess excellent antifriction and antiwear performance as water-based lubricant additive with a low concentration of 0.3 mg/mL under atmospheric condition. The friction coefficients can be <0.01, achieving superlubrication. Further systematical investigations on the wear traces, wear debris, and counter balls propose a “dispersion-compensation-filling repairment” friction mechanism. All these results demonstrate that h-BNNSs can achieve superlubrication as water-based lubricant additives via facile surface modification, making them very promising candidates as lubricant additives in practical applications.
  • Recycled Poly(ethylene terephthalate) for High Temperature Solvent Resistant Membranes

    Pulido, Bruno; Habboub, Ola; Aristizabal, Sandra; Szekely, Gyorgy; Nunes, Suzana Pereira (ACS Applied Polymer Materials, American Chemical Society (ACS), 2019-07-22) [Article]
    Porous membranes of recycled poly(ethylene terephthalate) (PET) were prepared by non-solvent induced phase separation (NIPS) and evaluated for the first time for the filtration in high temperature solvents and other harsh environments. The PET was recycled from commercial water bottles. The morphology, pore size and pore density were optimized by varying the composition of the polymer concentration in the casting solution, the solvent, and the non-solvent bath in conditions of controlled humidity and temperature. Poly(ethylene glycol) (PEG) of 0.2 and 1 kg mol-1 was used as an additive and pore inducing agent. The filtration performance of the membranes was tested under different solvents and temperatures. The obtained PET membranes were successfully applied for ultrafiltration with a MWCO of 40 kg mol-1 in dimethylformamide (DMF) at temperatures up to 100 ˚C. PET membranes were found to be resistant to a wide variety of solvents as well as in chlorine and acid medium. They could be used as porous support for thin-film composite membranes and for different applications requiring high chemical and heat resistance.
  • Enhancing supercapacitive performance of hierarchical carbon by introducing extra-framework cations

    Chen, Yuxiang; Shen, Man; Fu, Xin; Yao, Hong Chang; Zhang, Xianming; Liu, Yunqi; Liu, Xiaoying; Yao, Kexin (Materials Letters, Elsevier B.V., 2019-07-19) [Article]
    We design and prepare a novel hierarchical carbonaceous electrode material (SBA-C-K-N) for supercapacitor. The combination of micro/mesoporous structure and extra-framework cations endow SBA-C-K-N with outstanding electrochemical performance, including high specific capacitance of 134.4 F g−1 at 0.5 A g−1 and ideal rate capability. Meanwhile, 97.3% of the specific capacitance is well-maintained after 1000 cycles. Surprisingly, comprehensive characterization showed extra-framework cations (K+) could boost capacitance and decrease charge-transfer resistance, which might result from pre-fixed extra-framework cations decreased interfacial barrier between electrode surface and electrolyte and sped up mass transport between both phases.
  • Direct Imaging of Tunable Crystal Surface Structures of MOF MIL-101 Using High-Resolution Electron Microscopy

    Li, Xinghua; Wang, Jianjian; Liu, Xin; Liu, Lingmei; Cha, Dongkyu; Zheng, Xinliang; Yousef, Ali A.; Song, Kepeng; Zhu, Yihan; Zhang, Daliang; Han, Yu (Journal of the American Chemical Society, American Chemical Society (ACS), 2019-07-19) [Article]
    Metal–organic frameworks (MOFs) are often synthesized using various additives to modulate the crystallization. Here, we report the direct imaging of the crystal surface of MOF MIL-101 synthesized with different additives, using low-dose high-resolution transmission electron microscopy (HRTEM), and identify three distinct surface structures, at subunit cell resolution. We find that the mesoporous cages at the outermost surface of MIL-101 can be opened up by vacuum heating treatment at different temperatures, depending on the MIL-101 samples. We monitor the structural evolution of MIL-101 upon vacuum heating, using in situ X-ray diffraction, and find the results to be in good agreement with HRTEM observations, which leads us to speculate that additives have an influence not only on the surface structure but also on the stability of framework. In addition, we observe solid–solid phase transformation from MIL-101 to MIL-53 taking place in the sample synthesized with hydrofluoric acid.
  • Quantum-Dot-Derived Catalysts for CO2 Reduction Reaction

    Liu, Min; Liu, Mengxia; Wang, Xiaoming; Kozlov, Sergey; Cao, Zhen; De Luna, Phil; Li, Hongmei; Qiu, Xiaoqing; Liu, Kang; Hu, Junhua; Jia, Chuankun; Wang, Peng; Zhou, Huimin; He, Jun; Zhong, Miao; Lan, Xinzheng; Zhou, Yansong; Wang, Zhiqiang; Li, Jun; Seifitokaldani, Ali; Dinh, Cao Thang; Liang, Hongyan; Zou, Chengqin; Zhang, Daliang; Yang, Yang; Chan, Ting Shan; Han, Yu; Cavallo, Luigi; Sham, Tsun Kong; Hwang, Bing Joe; Sargent, Edward H. (Joule, Elsevier BV, 2019-07-17) [Article]
    Defect sites are often proposed as key active sites in the design of catalysts. A promising strategy for improving activity is to achieve a high density of homogeneously dispersed atomic defects; however, this is seldom accomplished in metals. We hypothesize that vacancy-rich catalysts could be obtained through the synthesis of quantum dots (QDs) and their electrochemical reduction during the CO2 reduction reaction (CO2RR). Here, we report that QD-derived catalysts (QDDCs) with up to 20 vol % vacancies achieve record current densities of 16, 19, and 25 mAcm−2 with high faradic efficiencies in the electrosynthesis of formate, carbon monoxide, and ethylene at low potentials of –0.2, –0.3, and –0.9 V versus reversible hydrogen electrode (RHE), respectively. The materials are stable after 80 hr of CO2RR. These CO2RR performances in aqueous solution surpass those of previously reported catalysts by 2×. Together, X-ray absorption spectroscopy and computational studies reveal that the vacancies produce a local atomic and electronic structure that enhances CO2RR.
  • Towards cleaner PolarClean: efficient synthesis and extended applications of the polar aprotic solvent methyl 5-(dimethylamino)-2-methyl-5-oxopentanoate

    Cseri, Levente; Szekely, Gyorgy (Green Chemistry, Royal Society of Chemistry (RSC), 2019-07-12) [Article]
    As a result of recent efforts in green solvent selection, methyl 5-(dimethylamino)-2-methyl-5-oxopentanoate, sold under the brand name Rhodiasolv PolarClean, has received considerable scientific and industrial attention as a possible non-toxic replacement for common polar aprotic solvents. However, the multicomponent nature and multi-step synthesis of this solvent remains an obstacle for its more widespread use and niche applications. In this work, a retrosynthetic approach was taken to identify novel shorter synthetic routes in alignment with green chemistry principles. High purity methyl 5-(dimethylamino)-2-methyl-5-oxopentanoate was obtained in novel single-step reactions via two different base-catalysed Michael additions from readily available building blocks. The more advanced synthetic route shows great potential owing to the swift (30 min), solvent-free reaction and catalytic amounts of base (<6.5 mol%). Green metrics analysis, including Atom Economy, Complete E factor, Carbon Intensity and hazard analysis found the new synthesis to be more sustainable than the patented routes. Application of this green solvent was demonstrated for the first time for O- and N-arylation in SNAr reaction with solvent recovery with similar or superior yields compared to other green solvents. Moreover, broad opportunities for this green solvent in membrane science were identified, where the use of conventional, toxic polar aprotic solvents in large quantities is unavoidable. Important practical solvent properties and parameters such as dielectric constant, solubility parameters, solvent miscibility and NMR residual shifts have been determined to facilitate the uptake of methyl 5-(dimethylamino)-2-methyl-5-oxopentanoate as a green solvent.

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