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1. CO organization at ambient pressure on stepped Pt surfaces: first principles modeling accelerated by neural networks

   https://doi.org/10.1039/d1sc03827c  

   Sumaria, Vaidish; Sautet, Philippe (December 2021, Chemical Science)

   Step and kink sites at Pt surfaces have crucial importance in catalysis. We employ a high dimensional neural network potential (HDNNP) trained using first-principles calculations to determine the adsorption structure of CO under ambient conditions ( T = 300 K and P = 1 atm) on these surfaces. To thoroughly explore the potential energy surface (PES), we use a modified basin hopping method. We utilize the explored PES to identify the adsorbate structures and show that under the considered conditions several low free energy structures exist. Under the considered temperature and pressure conditions, the step edge (or kink) is totally occupied by on-top CO molecules. We show that the step structure and the structure of CO molecules on the step dictate the arrangement of CO molecules on the lower terrace. On surfaces with (111) steps, like Pt(553), CO forms quasi-hexagonal structures on the terrace with the top site preferred, with on average two top site CO for one multiply bonded CO, while in contrast surfaces with (100) steps, like Pt(557), present a majority of multiply bonded CO on their terrace. Short terraced surfaces, like Pt(643), with square (100) steps that are broken by kink sites constrain the CO arrangement parallel to the step edge. Overall, this effort provides detailed analysis on the influence of the step edge structure, kink sites, and terrace width on the organization of CO molecules on non-reconstructed stepped surfaces, yielding initial structures for understanding restructuring events driven by CO at high coverages and ambient pressure. 

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2. A Heteromeric Carboxylic‐acid‐based Single Crystalline Crosslinked Organic Framework

   https://doi.org/10.1002/anie.202109987  

   Liang, Rongran; Samanta, Jayanta; Shao, Baihao; Zhang, Mingshi; Staples, Richard; Chen, Albert; Tang, Miao; Wu, Yuyang; Aprahamian, Ivan; Ke, Chenfeng (August 2021, Angewandte Chemie International Edition)

   null (Ed.)

   The development of large pore single-crystalline covalently linked organic frameworks is critical in revealing the detailed structure-property relationship with substrates. One emergent approach is to photo-crosslink hydrogen-bonded molecular crystals. Introducing complementary hydrogen-bonded carboxylic acid building blocks is promising to construct large pore networks, but these molecules often form interpenetrated networks or non-porous solids. Herein, we introduced heteromeric carboxylic acid dimers to construct a non-interpenetrated molecular crystal. Crosslinking this crystal precursor with dithiols afforded a large pore single-crystalline hydrogen-bonded crosslinked organic framework HCOF-101. X-ray diffraction analysis revealed HCOF-101 as an interlayer connected hexagonal network, which possesses flexible linkages and large porous channels to host a hydrazone photoswitch. Multicycle Z/E-isomerization of the hydrazone took place reversibly within HCOF-101, showcasing the potential use of HCOF-101 for optical information storage. 

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3. High-Pressure Infiltration–Expulsion of Aqueous NaCl in Planar Hydrophobic Nanopores

   https://doi.org/10.1021/acs.jpcc.0c07184  

   Zamfir, Serban; Moucka, Filip; Bratko, Dusan (October 2020, The Journal of Physical Chemistry C)

   Permeation of water in a poorly wettable material results in a conversion of pressure/volume work into surface free energy representing a novel form of energy storage. The addition of salt increases the amount of stored energy and can reduce the hysteresis of the infiltration−expulsion cycle. Our molecular simulations provide a theoretical perspective into the mechanisms involved in the process and underlying structures and interactions in compressed nanoconfined solutions. We consider aqueous NaCl in nanosized confinements at pressures of up to 3 kbar. Open ensemble Monte Carlo simulations utilizing fractional exchanges of molecules for efficient addition−removal of ions have been utilized in conjunction with pressure-dependent chemical potentials to model bulk phases under pressure. Confinements open to these pressurized bulk, aqueous electrolyte phases show reversibility at narrow pore sizes and irreversibility in wider ones, consistent with experiment. The addition of salt increases in the solid−liquid interfacial tension in narrower pores and associated infiltration and expulsion pressures. These changes are consistent with strong desalination effects at the lower pore size observed irrespective of external pressure and initial concentration. 

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4. Organic metabolite uptake by Diazotrophs in the North Pacific Ocean

   https://doi.org/10.1093/ismeco/ycaf061  

   Filella, Alba; Cébron, Aurélie; Paix, Benoît; Vallet, Marine; Martinot, Pauline; Guyomarch, Léa; Guigue, Catherine; Tedetti, Marc; Grosso, Olivier; Turk-Kubo, Kendra A; et al (May 2025, ISME Communications)

   Abstract Dinitrogen (N₂) fixation by diazotrophs supports ocean productivity. Diazotrophs include photoautotrophic cyanobacteria, non-cyanobacterial diazotrophs (NCDs) and the recently discovered N2-fixing haptophyte. While NCDs are ubiquitous in the ocean, their ecology and metabolism remain largely unknown. Unlike cyanobacterial diazotrophs and the haptophyte, NCDs are primarily heterotrophic and depend on dissolved organic matter (DOM) for carbon and energy. However, conventional DOM amendment incubations do not allow discerning how different diazotrophs use DOM molecules, limiting our knowledge on DOM-diazotroph interactions. To identify diazotrophs using DOM, we amended North Pacific microbial communities with 13C-labeled DOM from phytoplankton cultures that was molecularly characterized, revealing the dominance of nitrogen-rich compounds. After DOM additions, we observed a community shift from cyanobacterial diazotrophs like Crocosphaera and Trichodesmium to NCDs at stations where the N2-fixing haptophyte abundance was relatively low. Through DNA stable isotope probing and gene sequencing, we identified diverse diazotrophs capable of taking up DOM. Our findings highlight unexpected DOM uptake by the haptophyte’s nitroplast, changes in community structure, and previously unrecognized osmotrophic behavior in NCDs, shaped by local biogeochemical conditions. 

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5. Promising Bialkali Bismuthides Cs(Na, K)2Bi for High-Performance Nanoscale Electromechanical Devices: Prediction of Mechanical and Anisotropic Elastic Properties under Hydrostatic Tension and Compression and Tunable Auxetic Properties

   https://doi.org/10.3390/nano11102739  

   Yalameha, Shahram; Nourbakhsh, Zahra; Ramazani, Ali; Vashaee, Daryoosh (October 2021, Nanomaterials)

   Using first-principles calculations, we predict highly stable cubic bialkali bismuthides Cs(Na, K)2Bi with several technologically important mechanical and anisotropic elastic properties. We investigate the mechanical and anisotropic elastic properties under hydrostatic tension and compression. At zero pressure, CsK2Bi is characterized by elastic anisotropy with maximum and minimum stiffness along the directions of [111] and [100], respectively. Unlike CsK2Bi, CsNa2Bi exhibits almost isotropic elastic behavior at zero pressure. We found that hydrostatic tension and compression change the isotropic and anisotropic mechanical responses of these compounds. Moreover, the auxetic nature of the CsK2Bi compound is tunable under pressure. This compound transforms into a material with a positive Poisson’s ratio under hydrostatic compression, while it holds a large negative Poisson’s ratio of about −0.45 along the [111] direction under hydrostatic tension. An auxetic nature is not observed in CsNa2Bi, and Poisson’s ratio shows completely isotropic behavior under hydrostatic compression. A directional elastic wave velocity analysis shows that hydrostatic pressure effectively changes the propagation pattern of the elastic waves of both compounds and switches the directions of propagation. Cohesive energy, phonon dispersion, and Born–Huang conditions show that these compounds are thermodynamically, mechanically, and dynamically stable, confirming the practical feasibility of their synthesis. The identified mechanisms for controlling the auxetic and anisotropic elastic behavior of these compounds offer a vital feature for designing and developing high-performance nanoscale electromechanical devices. 

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