Publications

Abstract We study the most luminous known supernova (SN) associated with a gamma-ray burst (GRB), SN 2011kl. The photospheric velocity of SN 2011kl around peak brightness is 21,000 ± 7000 km s −1 . Owing to different assumptions related to the light-curve (LC) evolution (broken or unbroken power-law function) of the optical afterglow of GRB 111209A, different techniques for the LC decomposition, and different methods (with or without a near-infrared contribution), three groups derived three different bolometric LCs for SN 2011kl. Previous studies have shown that the LCs without an early-time excess preferred a magnetar model, a magnetar+ 56 Ni model, or a white dwarf tidal disruption event model rather than the radioactive heating model. On the other hand, the LC shows an early-time excess and dip that cannot be reproduced by the aforementioned models, and hence the blue-supergiant model was proposed to explain it. Here, we reinvestigate the energy sources powering SN 2011kl. We find that the two LCs without the early-time excess of SN 2011kl can be explained by the magnetar+ 56 Ni model, and the LC showing the early excess can be explained by the magnetar+ 56 Ni model taking into account the cooling emission from the shock-heated envelope of the SN progenitor, demonstrating that this SN might primarily be powered by a nascent magnetar.

We present a strategy whereby selective formation of imine covalent organic frameworks (COFs) based on linking of triangles and squares into the <b>fjh</b> topology was achieved by the conformational design of the building units. 1,3,5-Trimethyl-2,4,6-tris(4-formylphenyl)benzene (TTFB, triangle) and 1,1,2,2-tetrakis(4-aminophenyl)ethene (ETTA, square) were reticulated into [(TTFB)₄(ETTA)₃]_<i>imine</i>, termed COF-790, which was fully characterized by spectroscopic, microscopic, and X-ray diffraction techniques. COF-790 exhibits permanent porosity and a Brunauer-Emmett-Teller (BET) surface area of 2650 m² g^-1. Key to the formation of this COF in crystalline form is the pre-designed conformation of the triangle and the square units to give dihedral angles in the range of 75-90°, without which the reaction results in the formation of amorphous product. We demonstrate the versatility of our strategy by also reporting the synthesis and characterization of two isoreticular forms of COF-790, COF-791 and COF-792, based on other square building units.

Cu-exchanged Y zeolite was investigated in order to determine the location of the copper cations relative to the zeolite framework and to determine which Cu cations are active for the oxidative carbonylation of methanol to dimethyl carbonate (DMC). Cu-Y zeolite was prepared by vapor-phase exchange of H-Y with CuCl. The oxidation state, local coordination, and bond distances of Al and Cu were determined using Al K-edge and Cu K-edge X-ray absorption spectroscopy (XAS). Complimentary information was obtained by H2 temperature-programmed reduction and by in-situ infrared spectroscopy. Cu-Y has a Cu/Al ratio of unity and very little occluded CuCl. The average Al-O and Al-Cu bond distances are 1.67 angstroms and 2.79 angstroms, respectively, and the average Cu-O and Cu-Si(Al) bond distances are 1.99 angstroms and 3.13 angstroms, respectively. All of the Cu exchanged is present as Cu+ in sites I', II, and III'. Cu-Y is active for the oxidative carbonylation of methanol, and at low reactant contact time produces DMC as the primary product. With increasing reactant contact time, DMC formation decreases in preference to the formation of dimethoxy methane (DMM) and methylformate (MF). The formation of DMM and MF is attributed to the hydrogenation of DMC and the hydrogenolysis of DMM, respectively. Observation of the catalyst under reaction conditions reveals that most of the copper cations remain as Cu+, but some oxidation of Cu+ to Cu2+ does occur. It is also concluded that only those copper cations present in site II and III' positions are accessible to the reactants, and hence are catalytically active. The dominant adsorbed species on the surface are methoxy groups, and adsorbed CO is present as a minority species. The relationship of these observations to the kinetics of DMC synthesis is discussed.

Tissues are composed of diverse cell subpopulations each with distinct metabolic characteristics that influence overall behavior. Unfortunately, traditional histopathology imaging techniques are 'blind' to the spatially ordered metabolic dynamics within tissue. While mass spectrometry imaging enables spatial mapping of molecular composition, resulting images are only a static snapshot in time of molecules involved in highly dynamic processes; kinetic information of flux through metabolic pathways is lacking. To address this limitation, we developed kinetic mass spectrometry imaging (kMSI), a novel technique integrating soft desorption/ionization mass spectrometry with clinically accepted in vivo metabolic labeling of tissue with deuterium to generate images of kinetic information of biological processes. Applied to a tumor, kMSI revealed heterogeneous spatial distributions of newly synthesized versus pre-existing lipids, with altered lipid synthesis patterns distinguishing region-specific intratumor subpopulations. Images also enabled identification and correlation of metabolic activity of specific lipids found in tumor regions of varying grade.

A linker extension strategy for generating metal-organic frameworks (MOFs) with superior moisture-capturing properties is presented. Applying this design approach involving experiment and computation results in MOF-LA2-1 {[Al(OH)(PZVDC)], where PZVDC^2- is (<i>E</i>)-5-(2-carboxylatovinyl)-1<i>H</i>-pyrazole-3-carboxylate}, which exhibits an approximately 50% water capacity increase compared to the state-of-the-art water-harvesting material MOF-303. The power of this approach is the increase in pore volume while retaining the ability of the MOF to harvest water in arid environments under long-term uptake and release cycling, as well as affording a reduction in regeneration heat and temperature. Density functional theory calculations and Monte Carlo simulations give detailed insight pertaining to framework structure, water interactions within its pores, and the resulting water sorption isotherm.

Molecules containing trifluoromethoxyaryl groups are of interest in pharmaceutical, agrochemical, and materials science research, due to their unique physical and electronic properties. Many of the known methods to synthesize aryl trifluoromethyl ethers require harsh reagents and highly controlled reaction conditions and rarely occur when heteroaromatic units are present. The two-step <i>O</i>-trifluoromethylation of phenols via aryl xanthates is one such method that suffers from these drawbacks. Herein, we report a method for the synthesis of aryl trifluoromethyl ethers from phenols by the facile conversion of the phenol to the corresponding aryl and heteroaryl xanthates with newly synthesized imidazolium methylthiocarbonothioyl salts and conversion of these xanthates to the trifluoromethyl ethers under mild reaction conditions.

In this third paper in a series we compare spectral feature measurements to\nphotometric properties of 108 low-redshift (z &lt; 0.1) Type Ia supernovae (SNe\nIa) with optical spectra within 5 d of maximum brightness. We find the\npseudo-equivalent width (pEW) of the Si II 4000 line to be a good indicator of\nlight-curve width, and the pEWs of the Mg II and Fe II complexes are relatively\ngood proxies for SN colour. We also employ a combination of light-curve\nparameters (specifically the SALT2 stretch and colour parameters x_1 and c,\nrespectively) and spectral measurements to calculate distance moduli. The\nresiduals from these models are then compared to the standard model which uses\nonly light-curve stretch and colour. Our investigations show that a distance\nmodel that uses x_1, c, and the velocity of the Si II 6355 feature does not\nlead to a decrease in the Hubble residuals. We also find that distance models\nwith flux ratios alone or in conjunction with light-curve information rarely\nperform better than the standard (x_1,c) model. However, when adopting a\ndistance model which combines the ratio of fluxes near ~3750 Ang. and ~4550\nAng. with both x_1 and c, the Hubble residuals are decreased by ~10 per cent,\nwhich is found to be significant at about the 2-sigma level. The weighted\nroot-mean-square of the residuals using this model is 0.130 +/- 0.017 mag (as\ncompared with 0.144 +/- 0.019 mag when using the same sample with the standard\nmodel). This Hubble diagram fit has one of the smallest scatters ever published\nand at the highest significance ever seen in such a study. Finally, these\nresults are discussed with regard to how they can improve the cosmological\naccuracy of future, large-scale SN Ia surveys. [Abridged]\n

We investigate the mechanism for the electrocatalytic generation of hydrogen from water by the molecular molybdenum-oxo complex, [(PY5Me(2))MoO](2+) (PY5Me(2) = 2,6-bis(1,1-bis(2-pyridyl)ethyl)pyridine). Computational and experimental evidence suggests that the electrocatalysis consists of three distinct electrochemical reductions, which precede the onset of catalysis. Cyclic voltammetry studies indicate that the first two reductions are accompanied by protonations to afford the Mo-aqua complex, [(PY5Me(2))Mo(OH(2))](+). Calculations support hydrogen evolution from this complex upon the third reduction, via the oxidative addition of a proton from the bound water to the metal center and finally an α-H abstraction to release hydrogen. Calculations further suggest that introducing electron-withdrawing substituents such as fluorides in the para positions of the pyridine rings can reduce the potential associated with the reductive steps, without substantially affecting the kinetics. After the third reduction, there are kinetic bottlenecks to the formation of the Mo-hydride and subsequent hydrogen release. Computational evidence also suggests an alternative to direct α-H abstraction as a mechanism for H(2) release which exhibits a lower barrier. The new mechanism is one in which a water acts as an intramolecular proton relay between the protons of the hydroxide and the hydride ligands. The calculated kinetics are in reasonable agreement with experimental measurements. Additionally, we propose a mechanism for the stoichiometric reaction of [(PY5Me(2))Mo(CF(3)SO(3))](+) with water to yield hydrogen and [(PY(5)Me(2))MoO](2+) along with the implications for the viability of an alternate catalytic cycle involving just two reductions to generate the active catalyst.

In silico materials design has long faced a fundamental tradeoff between accuracy, universality, and efficiency. In 2022, we pioneered the concept of a universal machine learning interatomic potential (UMLIP) [Chen &amp; Ong, Nat. Comput. Sci., 2022, 2, 718–728] – a foundational materials model (FMM) with comprehensive coverage of the periodic table. FMMs enable accurate, large-scale simulations across a broad spectrum of materials, offering transformative potential for materials discovery and design. More recently, the field has seen a trend toward increasingly complex FMM architectures—often with over 10 million parameters—trained on datasets exceeding 100 million structures, driven largely by major tech companies like Google DeepMind, Microsoft, and various startups. In this talk, I challenge the prevailing “bigger is better” paradigm in FMM development. I will present MatPES, a foundational, community-curated potential energy surface (PES) dataset of ~400,000 structures. Leveraging MatPES, we demonstrate that gains in FMM performance are primarily driven by data quality, and there are no “accuracy moat” in FMM architectures. Models trained on MatPES match or exceed the accuracy of previous FMMs across a diverse set of equilibrium, near-equilibrium, and dynamic benchmarks. Finally, I will argue that the key priorities in architectural and algorithmic development should be in the parallelization and scaling of such FMMs in high performance computing and their integration in high-throughput materials workflows.

Energy conversion: A cobalt redox mediator, [Co(bpyPY4)]2+/3+, based on a hexadentate polypyridyl ligand, was developed. Dye-sensitized solar cells (DSCs) made with this redox mediator showed improved stability and slightly higher efficiencies compared to [Co(bpy)3]2+/3+-based devices. Long-term stability evaluation of DSCs based on [Co(bpyPY4)]2+/3+ revealed excellent stability under full irradiation conditions (see picture). As a service to our authors and readers, this journal provides supporting information supplied by the authors. Such materials are peer reviewed and may be re-organized for online delivery, but are not copy-edited or typeset. Technical support issues arising from supporting information (other than missing files) should be addressed to the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.