Understanding the Mechanisms of CO₂ Adsorption Enhancement in Pure Silica Zeolites under Humid Conditions

Using grand canonical Monte Carlo simulations, computational screening of hundreds of pure silica zeolites were conducted to identify materials that show enhanced CO₂ uptake under humid conditions. Herein, we show that CO₂ adsorption performance can be either enhanced or degraded depending on the CO₂/H₂O binding site separations and characteristics of CO₂–H₂O interaction energies. As expected, CO₂ adsorption capacity is significantly degraded when its binding sites overlap with the H₂O sites. On the other hand, CO₂ adsorption performance is enhanced when CO₂/H₂O binding sites are clearly separated as shown from the molecular simulations. However, we show that there are zeolite structures where CO₂ enhancement is observed despite the close distance between the CO₂ and H₂O binding sites. It is demonstrated that favorable long-range Coulomb interaction between CO₂ and H₂O molecules is responsible for enhanced CO₂ adsorption performance in these materials

In Silico Generation of Chromium-Based MOFs with Abundant Active Sites for N₂/CH₄ Separation

Selective nitrogen capture from natural gas using the adsorption properties of porous materials is promising due to its environmental benefits. However, N2 removal from N2/CH4 mixtures has been quite challenging because of their similar physical properties. Targeting the Cr-trimer-based cluster with an open metal site, known for selective nitrogen capture through the π-back-bonding mechanism, we screened nearly one hundred thousand chromium trimer-based metal–organic frameworks (MOFs), both experimentally synthesized and computationally constructed. Using criteria such as Cr-density, polymorphism, resistance to activation, and separation performance, we identified a promising in silico MOF. This hypothetical MOF showed a simulated nitrogen uptake of 2.13 mmol/g and a selectivity of 10.2 at 1 bar, surpassing the performance of the previously known best-performing MOF, Cr-MIL-100

In Silico Generation of Chromium-Based MOFs with Abundant Active Sites for N₂/CH₄ Separation

Selective nitrogen capture from natural gas using the adsorption properties of porous materials is promising due to its environmental benefits. However, N2 removal from N2/CH4 mixtures has been quite challenging because of their similar physical properties. Targeting the Cr-trimer-based cluster with an open metal site, known for selective nitrogen capture through the π-back-bonding mechanism, we screened nearly one hundred thousand chromium trimer-based metal–organic frameworks (MOFs), both experimentally synthesized and computationally constructed. Using criteria such as Cr-density, polymorphism, resistance to activation, and separation performance, we identified a promising in silico MOF. This hypothetical MOF showed a simulated nitrogen uptake of 2.13 mmol/g and a selectivity of 10.2 at 1 bar, surpassing the performance of the previously known best-performing MOF, Cr-MIL-100

In Silico Generation of Chromium-Based MOFs with Abundant Active Sites for N₂/CH₄ Separation

Selective nitrogen capture from natural gas using the adsorption properties of porous materials is promising due to its environmental benefits. However, N2 removal from N2/CH4 mixtures has been quite challenging because of their similar physical properties. Targeting the Cr-trimer-based cluster with an open metal site, known for selective nitrogen capture through the π-back-bonding mechanism, we screened nearly one hundred thousand chromium trimer-based metal–organic frameworks (MOFs), both experimentally synthesized and computationally constructed. Using criteria such as Cr-density, polymorphism, resistance to activation, and separation performance, we identified a promising in silico MOF. This hypothetical MOF showed a simulated nitrogen uptake of 2.13 mmol/g and a selectivity of 10.2 at 1 bar, surpassing the performance of the previously known best-performing MOF, Cr-MIL-100

Size-Matching Ligand Insertion in MOF-74 for Enhanced CO₂ Capture under Humid Conditions

Among various class of materials, metal organic frameworks (MOFs) are one of the most promising candidates for CO₂ capture from flue gases. In particular, M-MOF-74, where M represents different metals, are equipped with open metal sites that can lead to very high CO₂ uptake at postcombustion flue gas conditions. However, these structures are known to have poor CO₂ capture performance under humid conditions as water molecules bind strongly to the unsaturated metal sites, outcompeting the CO₂. In this computational study, a pore space partition strategy is employed through a symmetry-matching regulated ligand insertion within the Mg-MOF-74 and Zn-MOF-74 structures, which mitigates the deterioration effect of water. In the case of Zn-MOF-74, higher selectivity as well as larger CO₂ uptake in binary mixture conditions is obtained, thereby demonstrating that reduction in the pore size of MOFs can serve as viable strategy to capture CO₂ under humid postcombustion conditions

Large-Scale Screening of Zeolite Structures for CO₂ Membrane Separations

We have conducted large-scale screening of zeolite materials for CO₂/CH₄ and CO₂/N₂ membrane separation applications using the free energy landscape of the guest molecules inside these porous materials. We show how advanced molecular simulations can be integrated with the design of a simple separation process to arrive at a metric to rank performance of over 87 000 different zeolite structures, including the known IZA zeolite structures. Our novel, efficient algorithm using graphics processing units can accurately characterize both the adsorption and diffusion properties of a given structure in just a few seconds and accordingly find a set of optimal structures for different desired purity of separated gases from a large database of porous materials in reasonable wall time. Our analysis reveals that the optimal structures for separations usually consist of channels with adsorption sites spread relatively uniformly across the entire channel such that they feature well-balanced CO₂ adsorption and diffusion properties. Our screening also shows that the top structures in the predicted zeolite database outperform the best known zeolite by a factor of 4–7. Finally, we have identified a completely different optimal set of zeolite structures that are suitable for an inverse process, in which the CO₂ is retained while CH₄ or N₂ is passed through a membrane

Surface Plasmon Aided Ethanol Dehydrogenation Using Ag–Ni Binary Nanoparticles

Plasmonic metal nanoparticles absorb light energy and release the energy through radiative or nonradiative channels. Surface catalytic reactions take advantage of the nonradiative energy relaxation of plasmons with enhanced activity. Particularly, binary nanoparticles are interesting because diverse integration is possible, consisting of a plasmonic part and a catalytic part. Herein, we demonstrated ethanol dehydrogenation under light irradiation using Ag–Ni binary nanoparticles with different shapes, snowman and core–shell, as plasmonic catalysts. The surface plasmon formed in the Ag part enhanced the surface catalytic reaction that occurred at the Ni part, and the shape of the nanoparticles affected the extent of the enhancement. The surface plasmon compensated the thermal energy required to trigger the catalytic reaction. The absorbed light energy was transferred to the catalytic part by the surface plasmon through the nonradiative hot electrons. The effective energy barrier was greatly reduced from 41.6 kJ/mol for the Ni catalyst to 25.5 kJ/mol for the core–shell nanoparticles and 22.3 kJ/mol for the snowman-shaped nanoparticles. These findings can be helpful in designing effective plasmonic catalysts for other thermally driven surface reactions

Three-dimensional reflectance traction microscopy applied to a mechanically deformed collagen matrix.

<p>(A) Schematic illustration of the experimental setup with side view (i) and top view (ii). A polydimethylsiloxane (PDMS) channel (20 mm × 3 mm) is in contact with collagen gel and is inflated with air. When air is released, the squeezed collagen gel relaxes to a stress-free state, resulting in a deformation field which is expected to follow the arrows in (i) and (ii). The red rectangle encloses the volume of the confocal imaging field of view. (B) The 3D deformation field calculated with PVC algorithm. Deformation along z-axis (<i>D</i>_<i>z</i>) of three selected cross-sections (corresponding to the green lines in A(ii)) are shown as color maps. The lateral deformation field (<i>D</i>_<i>x</i> and <i>D</i>_<i>y</i>) of a selected horizontal cross-section is shown as arrows. The arrows are color coded by the magnitude of the lateral deformation field .</p

Transferability of CO₂ Force Fields for Prediction of Adsorption Properties in All-Silica Zeolites

We present a systematic and comprehensive investigation of available CO₂ force fields for their predictions of adsorption properties in 156 geometrically diverse zeolite structures. The comparison reveals that a large discrepancy in the predicted properties, by more than 2 orders of magnitude, may exist. Especially, variation predicted by different force fields appears to be more pronounced for zeolites with more confined pore features, which can be attributed to the repulsive characteristics of force fields. The discrepancy especially impacts zeolites that are deemed to be the best materials for carbon capture and sequestration (CCS), indicating that the predictions on the best materials can drastically differ, based on the choice of force fields. To develop accurate and fully transferable force fields, in this work, we show that the inclusion of adsorption uptake at a high-pressure region (or saturation loading), as well as the diffusion coefficient, can be of utmost importance. These properties can be used as indicators for the repulsive behaviors between gas molecules and the framework. Mixture isotherms have also been identified to be potentially useful for the same purpose. Moreover, we have also demonstrated that interaction energies computed by ab initio methods can be useful references to ensure a newly developed force field is capable of describing the energy surface at an atomic level. Overall, the outcomes of this study will be instrumental to the future development of accurate and transferrable force fields, which is critical for future large-scale computational studies

Three-dimensional reflectance traction microscopy reveals the traction field of breast cancer cells in 3D collagen matrix.

<p>(A-D) The strain magnitude <i>ε</i> and deformation field <b>D</b> measured around four isolated MDA-MB-231 cells before and after the cells are treated with cytochalsin-D. <i>ε</i> of orthogonal cross-sections are shown as color maps. <b>D</b> projected on to these cross-sections are shown as arrows. The cell surfaces (illuminated red surfaces) are reconstructed from isosurface rendering of fluorescently labeled cytoplasms. The arrows are color coded by the magnitude of the projected deformation fields. (A) and (B) demonstrate deformation and strain fields around cells with rounded morphology. (C) and (D) show the results around cells with larger aspect ratios.</p