| 1. |
- Bermejo-López, Aitor, et al.
(författare)
-
Selective Synthesis of Imines by Photo-Oxidative Amine Cross-Condensation Catalyzed by PCN-222(Pd)
- 2021
-
Ingår i: ACS Sustainable Chemistry and Engineering. - : American Chemical Society (ACS). - 2168-0485. ; 9:43, s. 14405-14415
-
Tidskriftsartikel (refereegranskat)abstract
- Palladium-metalated PCN-222 enables the aerobic photo-oxidative cross-condensation of anilines with benzylic amines yielding a series of linear and cyclic imines. The reaction is very efficient under mild conditions, which allows the isolation of simple, yet elusive, intermediates such as 2-(benzylideneamino)-aniline and 2-(benzylideneamino)phenols. Recyclability studies show excellent activity and selectivity after five runs. The methodology was successfully applied for the synthesis of an antitumor agent (PMX-610).
|
|
| 2. |
- Frank, Sara, et al.
(författare)
-
Exploring the influence of atomic level structure, porosity, and stability of bismuth(iii) coordination polymers on electrocatalytic CO2 reduction
- 2021
-
Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7488 .- 2050-7496. ; 9:46, s. 26298-26310
-
Tidskriftsartikel (refereegranskat)abstract
- Bismuth-based coordination polymers (CPs) have recently attracted attention as catalyst precursors for the electrocatalytic CO2 reduction reaction (eCO(2)RR). We present a comparative study by investigating six bismuth-based compounds in-depth to elucidate the correlation between their structures and their catalytic CO2-to-formate conversion. Thereby, we identify structural indicators of the pristine CPs resulting in optimized catalytic performance, paving the way for future design of CP derived catalysts. The structural properties of the six pristine materials vary in terms of porosity (from non-porous to 495 m(2) g(-1)), linker type (carboxylate- or phenolate-based), thermal- and chemical stability, and metal content. Herein, electrochemical studies are combined with comprehensive structural investigations using electron microscopy, powder X-ray diffraction, and X-ray absorption spectroscopy. Our study reveals that low chemical stability of the pristine CPs is crucial for the conversion of the precursors into active Bi2O2CO3 and of paramount importance for the eCO(2)RR activity, while the nature of the pristine material mostly influence the catalyst morphology and transport properties. Of the six investigated CPs, the best performing compounds selectively convert CO2 to formate with faradaic efficiencies in the range 80(3)-95(3)% and current densities of 5(1)-8(1) mA cm(-2) at -0.97 V-RHE.
|
|
| 3. |
- Jeppesen, Henrik S., et al.
(författare)
-
LiquidReactionCell - a versatile setup for in situ synchrotron studies of compounds in liquid suspension and solution
- 2022
-
Ingår i: CrystEngComm. - : Royal Society of Chemistry (RSC). - 1466-8033. ; 25:5, s. 751-760
-
Tidskriftsartikel (refereegranskat)abstract
- There is an increasing interest in understanding the atomic level formation of functional materials, e.g. through nucleation and growth from their precursors in solution or through chemically induced phase transitions. Such information is achievable though synchrotron-based in situ X-ray absorption spectroscopy (XAS) and total scattering (TS) experiments. In this study we present a new and versatile setup for in situ investigations of chemical reactions. Our setup, LiquidReactionCell (LRC), is constructed in borosilicate glass, i.e., it is chemically inert and transparent to visible light, and it resembles regular laboratory glassware. The setup is designed to handle homogenous solutions and fine powder suspensions at ambient conditions, and it can be used to follow chemically or light induced reactions, for example. Chemical precursors can be added during data collection, and inert conditions can be obtained in the cell. Herein, we demonstrate the versatility and use of the LRC in XAS and TS experiments. Specifically, we compare data collected on powder suspensions in the LRC with data measured on powders under ideal conditions. Bi24O31X10 (X = Cl, Br) are emerging materials for photocatalysis and are used as model compounds herein. Gratifyingly, only minor differences are observed between data collected on suspensions in the LRC and data collected on a pressed pellet (for XAS) or on a powder in a Kapton capillary (for TS). These results propose that the LRC has the potential to cover a broad range of chemical reactions.
|
|
| 4. |
- Lock, Nina, et al.
(författare)
-
Copper doped TiO2 nanoparticles characterized by X-ray absorption spectroscopy, total scattering, and powder diffraction - a benchmark structure-property study
- 2013
-
Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9234 .- 1477-9226. ; 42:26, s. 9555-9564
-
Tidskriftsartikel (refereegranskat)abstract
- Metal functionalized nanoparticles potentially have improved properties e. g. in catalytic applications, but their precise structures are often very challenging to determine. Here we report a structural benchmark study based on tetragonal anatase TiO2 nanoparticles containing 0-2 wt% copper. The particles were synthesized by continuous flow synthesis under supercritical water-isopropanol conditions. Size determination using synchrotron PXRD, TEM, and X-ray total scattering reveals 5-7 nm monodisperse particles. The precise dopant structure and thermal stability of the highly crystalline powders were characterized by X-ray absorption spectroscopy and multi-temperature synchrotron PXRD (300-1000 K). The combined evidence reveals that copper is present as a dopant on the particle surfaces, most likely in an amorphous oxide or hydroxide shell. UV-VIS spectroscopy shows that copper presence at concentrations higher than 0.3 wt% lowers the band gap energy. The particles are unaffected by heating to 600 K, while growth and partial transformation to rutile TiO2 occur at higher temperatures. Anisotropic unit cell behavior of anatase is observed as a consequence of the particle growth (a decreases and c increases).
|
|
| 5. |
- Lock, Nina, et al.
(författare)
-
Scrutinizing negative thermal expansion in MOF-5 by scattering techniques and ab initio calculations
- 2013
-
Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9234. ; 42:6, s. 1996-2007
-
Tidskriftsartikel (refereegranskat)abstract
- Complementary experimental techniques and ab initio calculations were used to determine the origin and nature of negative thermal expansion (NTE) in the archetype metal-organic framework MOF-5 (Zn4O(1,4-benzenedicarboxylate) (3)). The organic linker was probed by inelastic neutron scattering under vacuum and at a gas pressure of 175 bar to distinguish between the pressure and temperature responses of the framework motions, and the local structure of the metal centers was studied by X-ray absorption spectroscopy. Multi-temperature powder-and single-crystal X-ray and neutron diffraction was used to characterize the polymeric nature of the sample and to quantify NTE over the large temperature range 4-400 K. Ab initio calculations complement the experimental data with detailed information on vibrational motions in the framework and their correlations. A uniform and comprehensive picture of NTE in MOF-5 has been drawn, and we provide direct evidence that the main contributor to NTE is translational transverse motion of the aromatic ring, which can be dampened by applying a gas pressure to the sample. The linker motion is highly correlated rather than local in nature. The relative energies of different framework vibrations populated in MOF-5 are suggested by analysis of neutron diffraction data. We note that the lowest-energy motion is a librational motion of the aromatic ring which does not contribute to NTE. The libration is followed by transverse motion of the linker and the carboxylate group. These motions result in unit-cell contraction with increasing temperature.
|
|
