Volumetric Uptake Research Articles

In Situ, High-Resolution Quantification of CO2 Uptake Rates via Automated Off-Gas Analysis Illuminates Carbon Uptake Dynamics in Cyanobacterial Cultures.

Quantification of cyanobacterial CO2 fixation rates is vital to determining their potential as industrial strains in a circular bioeconomy. Currently, however, CO2 fixation rates are most often determined through indirect and/or low-resolution methods, resulting in an incomplete picture of both dynamic behaviors and total carbon fixation potential. To address this, we developed the "Automated Carbon and CO2 Experimental Sampling System" (ACCESS); a low-cost system for in situ off-gas analysis that supports the automated acquisition of high-resolution volumetric CO2 uptake rates from multiple cyanobacterial cultures in parallel. Carbon fixation data obtained via ACCESS were first independently validated by elemental analysis of cultivated biomass. Using ACCESS, we then demonstrate how the volumetric CO2 uptake rate of two model cyanobacteria, Synechococcus sp. PCC 7002 and Synechocystis sp. PCC 6803, accelerates linearly to a maximum before then decaying monotonically to cessation by stationary phase. Furthermore, consistent with the expected stoichiometry, strong correlations were also found to exist between cell growth and carbon fixation, both in terms of rates as well as total levels. The novel insights made possible via ACCESS will aid other cyanobacterial researchers in diverse fundamental and applied research efforts.

Ultrahigh-surface area covalent organic frameworks for methane adsorption.

Developing porous materials with ultrahigh surface areas for gas storage (for example, methane) is attractive but challenging. Here, we report two isostructural three-dimensional covalent organic frameworks (COFs) with a rare self-catenated alb-3,6-Ccc2 topology and a pore size of 1.1 nanometer. Notably, these imine-linked microporous COFs show both high gravimetric Brunauer-Emmett-Teller (BET) surface areas (~4400 square meters per gram) and volumetric BET surface areas (~1900 square meters per cubic centimeter). Moreover, their volumetric methane uptake reaches up to 264 cubic centimeter (standard temperature and pressure) per cubic centimeter [cm3 (STP) cm-3] at 100 bar and 298 kelvin, and they exhibit the highest volumetric working capacity of 237 cm3 (STP) cm-3 at 5 to 100 bar and 298 kelvin among all reported porous crystalline materials.

Construction of Highly Porous and Robust Hydrogen‐Bonded Organic Framework for High‐Capacity Clean Energy Gas Storage

AbstractDevelopment of highly porous and robust hydrogen‐bonded organic frameworks (HOFs) for high‐pressure methane and hydrogen storage remains a grand challenge due to the fragile nature of hydrogen bonds. Herein, we report a strategy of constructing the double‐walled framework to target highly porous and robust HOF (ZJU‐HOF‐5a) for extraordinary CH4 and H2 storage. ZJU‐HOF‐5a features a minimized twofold interpenetration with double‐walled structure, in which multiple supramolecular interactions are existed between the interpenetrated walls. This structural configuration can notably enhance the framework robustness while maintaining its high porosity, affording one of the highest gravimetric and volumetric surface areas of 3102 m2 g−1 and 1976 m2 cm−3 among the reported HOFs so far. ZJU‐HOF‐5a thus exhibits an extremely high volumetric H2 uptake of 43.6 g L−1 at 77 K/100 bar and working capacity of 41.3 g L−1 under combined swing conditions (77 K/100 bar→160 K/5 bar), and also impressive methane storage performance with a 5–100 bar working capacity of 187 (or 159) cm3 (STP) cm−3 at 270 K (or 296 K), outperforming most of the reported porous organic materials. Single‐crystal X‐ray diffraction studies on CH4‐loaded ZJU‐HOF‐5a reveal that abundant supramolecular binding sites combined with ultrahigh porosities account for its high CH4 storage capacities. Combined with high stability, super‐hydrophobicity, and easy recovery, ZJU‐HOF‐5a is placed among the most promising materials for H2 and CH4 storage applications.

Construction of Highly Porous and Robust Hydrogen-Bonded Organic Framework for High-Capacity Clean Energy Gas Storage.

Development of highly porous and robust hydrogen-bonded organic frameworks (HOFs) for high-pressure methane and hydrogen storage remains a grand challenge due to the fragile nature of hydrogen bonds. Herein, we report a strategy of constructing the double-walled framework to target highly porous and robust HOF (ZJU-HOF-5a) for extraordinary CH4 and H2 storage. ZJU-HOF-5a features a minimized twofold interpenetration with double-walled structure, in which multiple supramolecular interactions are existed between the interpenetrated walls. This structural configuration can notably enhance the framework robustness while maintaining its high porosity, affording one of the highest gravimetric and volumetric surface areas of 3102 m2 g-1 and 1976 m2 cm-3 among the reported HOFs so far. ZJU-HOF-5a thus exhibits an extremely high volumetric H2 uptake of 43.6 g L-1 at 77 K/100 bar and working capacity of 41.3 g L-1 under combined swing conditions (77 K/100 bar→160 K/5 bar), and also impressive methane storage performance with a 5-100 bar working capacity of 187 (or 159) cm3 (STP) cm-3 at 270 K (or 296 K), outperforming most of the reported porous organic materials. Single-crystal X-ray diffraction studies on CH4-loaded ZJU-HOF-5a reveal that abundant supramolecular binding sites combined with ultrahigh porosities account for its high CH4 storage capacities. Combined with high stability, super-hydrophobicity, and easy recovery, ZJU-HOF-5a is placed among the most promising materials for H2 and CH4 storage applications.

High Volumetric and Gravimetric Acetylene Uptakes in a Cu-MOF with Tailored Cages.

NTUniv-80 exhibits record-high volumetric and gravimetric acetylene (C2H2) uptakes of 210 cm3 (STP) g-1 and 227 cm3 (STP) cm-3 at 295 K and 1 atm, respectively. Grand canonical Monte Carlo (GCMC) simulation indicates that those remarkable C2H2 uptakes are attributed to the open Cu2+ sites and tailored cages.

Imaging bone turnover assessment through volumetric density-adjusted standardized uptake value using quantitative bone SPECT/CT in osteoporosis

BackgroundSerum bone turnover markers offer limited insight into metabolic activity at the individual vertebra level in osteoporosis. This study introduces a novel image-derived bone turnover marker for individual vertebrae to address this limitation, utilizing volumetric density-adjusted quantitative bone single-photon emission computed tomography/computed tomography (SPECT/CT) with [99mTc]Tc-DPD. This retrospective study included 177 lumbar vertebrae from 55 postmenopausal South Korean women. The mean standardized uptake value (SUVmean, g/cm3) and volumetric bone mineral density (vBMD, mg/cm3) were determined within a 2-cm³ volume of interest in the trabecular portion of each vertebra using quantitative SPECT and CT. The density-adjusted mean standardized uptake value (dSUVmean) was calculated by dividing the SUVmean by the vBMD and multiplying by 1,000.ResultsSUVmean correlated positively with vBMD (r = 0.60, p < 0.001). Conversely, dSUVmean correlated negatively with vBMD (ρ = −0.66, p < 0.001), highlighting the inverse relationship between bone mass and turnover after density adjustment of SUVmean. Patients with major osteoporotic fractures had lower vBMD (62.5 ± 29.4 vs. 92.3 ± 27.4 mg/cm³, p = 0.001) but higher dSUVmean (100.8 ± 60.7 vs. 62.6 ± 17.5, p = 0.001) compared to those without fractures, reinforcing the association between fracture prevalence, low bone mass, and high bone turnover.ConclusionVolumetric density-adjusted quantitative bone SPECT/CT offers a novel image-derived bone turnover marker for assessing bone turnover in osteoporosis. This method provides a precise assessment of fragility at the individual vertebra level, which may enhance personalized osteoporosis management.

Exploring Methane Storage Capacities of M2(BDC)2(DABCO) Sorbents: A Multiscale Computational Study

A promising solution for efficient methane (CH4) storage and transport is a metal–organic framework (MOF)-based sorbent. Hence, searching for potential MOFs like M2(BDC)2(DABCO) to enhance the CH4 storage capacity in both gravimetric and volumetric uptakes is essential. Herein, we systematically elucidate the adsorption of CH4 in M2(BDC)2(DABCO) or M(DABCO) (M = Mg, Mn, Fe, Co, Ni, Cu, Zn) MOFs using multiscale simulations that combined grand canonical Monte Carlo simulation with van der Waals density functional (vdW-DF) calculation. We find that, in the M(DABCO) series, Mg(DABCO) has the highest total CH4 adsorption capacities, with mtot= 231.39 mg/g at 298 K, for gravimetric uptake, and Vtot= 231.43 cc(STP)/cc, for volumetric uptake. The effects of temperature, pressure, and metal substitution on enhancing CH4 storage are evaluated, and we predict that the volumetric CH4 storage capacity on M(DABCO) could meet the DOE target at temperatures of ca. 238 K–268 K and pressures of 35–100 bar. The interactions between CH4 and M(DABCO) are dominated by the vdW interactions, as shown by the vdW-DF calculations. The Mg, Mn, Fe, Co, and Ni substitutions in M(DABCO) result in a stronger interaction and thus, a higher CH4 storage capacity, at higher pressures for Mg, Mn, Ni, and Co and at lower pressures for Fe. This work may provide guidance for the rational design of CH4 storage in M2(BDC)2(DABCO) MOFs.

Hydrogen storage in M(BDC)(TED)0.5 metal-organic framework: physical insights and capacities.

Finding renewable energy sources to replace fossil energy has been an essential demand in recent years. Hydrogen gas has been becoming a research hotspot for its clean and free-carbon energy. However, hydrogen storage technology is challenging for mobile and automotive applications. Metal-organic frameworks (MOFs) have emerged as one of the most advanced materials for hydrogen storage due to their exceptionally high surface area, ultra-large and tuneable pore size. Recently, computer simulations allowed the designing of new MOF structures with significant hydrogen storage capacity. However, no studies are available to elucidate the hydrogen storage in M(BDC)(TED)0.5, where M = metal, BDC = 1,4-benzene dicarboxylate, and TED = triethylenediamine. In this report, we used van der Waals-dispersion corrected density functional theory and grand canonical Monte Carlo methods to explore the electronic structure properties, adsorption energies, and gravimetric and volumetric hydrogen loadings in M(BDC)(TED)0.5 (M = Mg, V, Co, Ni, and Cu). Our results showed that the most favourable adsorption site of H2 in M(BDC)(TED)0.5 is the metal cluster-TED intersection region, in which Ni offers the strongest binding strength with the adsorption energy of -16.9 kJ mol-1. Besides, the H2@M(BDC)(TED)0.5 interaction is physisorption, which mainly stems from the contribution of the d orbitals of the metal atoms for M = Ni, V, Cu, and Co and the p orbitals of the O, C, N atoms for M = Mg interacting with the σ* state of the adsorbed hydrogen molecule. Noticeably, the alkaline-earth metal Mg strongly enhanced the specific surface area and pore size of the M(BDC)(TED)0.5 MOF, leading to an enormous increase in hydrogen storage with the highest absolute (excess) gravimetric and volumetric uptakes of 1.05 (0.36) wt% and 7.47 (2.59) g L-1 at 298 K and 7.42 (5.80) wt% and 52.77 (41.26) g L-1 at 77 K, respectively. The results are comparable to the other MOFs found in the literature.

Prediction of Hydrogen Adsorption and Moduli of Metal–Organic Frameworks (MOFs) Using Machine Learning Strategies

For hydrogen-powered vehicles, the efficiency cost brought about by the current industry choices of hydrogen storage methods greatly reduces the system’s overall efficiency. The physisorption of hydrogen fuel onto metal–organic frameworks (MOFs) is a promising alternative storage method due to their large surface areas and exceptional tunability. However, the massive selection of MOFs poses a challenge for the efficient screening of top-performing MOF structures that are capable of meeting target hydrogen uptakes. This study examined the performance of 13 machine learning (ML) models in the prediction of the gravimetric and volumetric hydrogen uptakes of real MOF structures for comparison with simulated and experimental results. Among the 13 models studied, 12 models gave an R2 greater than 0.95 in the prediction of both the gravimetric and the volumetric uptakes in MOFs. In addition, this study introduces a 4-20-1 ANN model that predicts the bulk, shear, and Young’s moduli for the MOFs. The machine learning models with high R2 can be used in choosing MOFs for hydrogen storage.

Porous carbon composites as clean energy materials with extraordinary methane storage capacity

Activated carbon composites containing alumina have high porosity (up to ∼2800 m2 g−1 and 1.5 cm3 g−1) and packing density (∼1 g cm−3), which translates to extraordinary methane volumetric uptake of up to 474 cm3 (STP) cm−3 at 25 °C and 100 bar.

Boosting Adsorption Isosteric Heat for Improved Gravimetric and Volumetric Hydrogen Uptake in Porous Carbon by N-Doping

Boosting Adsorption Isosteric Heat for Improved Gravimetric and Volumetric Hydrogen Uptake in Porous Carbon by N-Doping

Comparison of machine learning approaches for the identification of top-performing materials for hydrogen storage

Unique properties of Metal-Organic Frameworks (MOFs), such as their extremely high surface areas and porosity, render them as one of, if not the most promising adsorbents for gas storage applications. However, their extremely flexible and tunable nature has resulted in an enormous expansion of the available material pool which in turn begs the question as to whether an efficient identification of the best materials is feasible. In the last years, Machine Learning (ML) techniques have been extensively applied for the exploration of large material databases, since they can significantly accelerate this process. In this work, “traditional” ML models and models based on our recently developed iterative self-consistent approach are compared with respect to their ability to efficiently identify the best materials of a database. As a case study, we have used hydrogen adsorption in MOFs at different thermodynamic conditions. Despite their high accuracy, traditional models struggle to pinpoint the best materials, regarding usable gravimetric uptake, without compromising computational resources. On the other hand, self-consistent models can even reduce by two orders of magnitude the amount of reference data required for the identification of the best gravimetric materials compared to traditional ones. Notably, 300 training samples are enough for the SC models to correctly identify the top-100 gravimetric materials of a database. Nevertheless, both type of models underperform when they are queried for the top-performing materials with regards to usable volumetric uptake.

Constructing copper-organic framework with exceptionally high volumetric working capacity for efficient methane storage

Extensive efforts have been devoted to developing novel porous structures for methane storage with high volumetric uptake and volumetric working capacity. In this study, a NbO-type copper–organic framework (CMOF-1) was designed and synthesized. Notably, the CMOF-1 posses suitable nanocages decorated with carboxylate groups and nitrogen sites, exhibiting a remarkable volumetric uptake of 260 cm3 cm−3 (at 65 bar/298 K) and a volumetric working capacity of 202 cm3 cm−3 (from 5 to 65 bar). These values are comparable to those of the benchmark material HKUST-1 (267 cm3 cm−3 and 190 cm3 cm−3) and exceed those of the structural analogue ZJU-5a (249 cm3 cm−3 and 188 cm3 cm−3) under the same conditions. The grand canonical Monte Carlo simulations and density functional theory calculations reveal that the high methane volumetric uptake might be contributed by the open CuII sites and nanocages with suitable sizes/shapes and functional sites, which can enforce strong gas-framework and gas–gas interactions. The methodology presented in this work should envision potential practical applications in methane storage and could be generalized to design other novel materials for the storage of other gases like hydrogen.

Synergistic Nitrogen Binding Sites in a Metal‐Organic Framework for Efficient N2/O2 Separation

AbstractPorous materials with d3 electronic configuration open metal sites have been proved to be effective adsorbents for N2 capture and N2/O2 separation. However, the reported materials remain challenging to address the trade‐off between adsorption capacity and selectivity. Herein, we report a robust MOF, MIL‐102Cr, that features two binding sites, can synergistically afford strong interactions for N2 capture. The synergistic adsorption site exhibits a benchmark Qst of 45.0 kJ mol−1 for N2 among the Cr‐based MOFs, a record‐high volumetric N2 uptake (31.38 cm3 cm−3), and highest N2/O2 selectivity (13.11) at 298 K and 1.0 bar. Breakthrough experiments reveal that MIL‐102Cr can efficiently capture N2 from a 79/21 N2/O2 mixture, providing a record 99.99 % pure O2 productivity of 0.75 mmol g−1. In situ infrared spectroscopy and computational modelling studies revealed that a synergistic adsorption effect by open Cr(III) and fluorine sites was accountable for the strong interactions between the MOF and N2.

Synergistic Nitrogen Binding Sites in a Metal-Organic Framework for Efficient N2 /O2 Separation.

Porous materials with d3 electronic configuration open metal sites have been proved to be effective adsorbents for N2 capture and N2 /O2 separation. However, the reported materials remain challenging to address the trade-off between adsorption capacity and selectivity. Herein, we report a robust MOF, MIL-102Cr, that features two binding sites, can synergistically afford strong interactions for N2 capture. The synergistic adsorption site exhibits a benchmark Qst of 45.0 kJ mol-1 for N2 among the Cr-based MOFs, a record-high volumetric N2 uptake (31.38 cm3 cm-3 ), and highest N2 /O2 selectivity (13.11) at 298 K and 1.0 bar. Breakthrough experiments reveal that MIL-102Cr can efficiently capture N2 from a 79/21 N2 /O2 mixture, providing a record 99.99 % pure O2 productivity of 0.75 mmol g-1 . In situ infrared spectroscopy and computational modelling studies revealed that a synergistic adsorption effect by open Cr(III) and fluorine sites was accountable for the strong interactions between the MOF and N2 .

Hydrate-based adsorption-hydration hybrid approach enhances methane storage in wet MIL-101(Cr)@AC under mild condition

Hydrate-based adsorption and hydration natural gas (AHNG) technology was reported to achieve large methane storage density under mild conditions. In order to enhance methane uptake, a composite nano porous material of MIL-101(Cr)@AC was prepared through fluorine-free hydrothermal reaction, and methane adsorption isotherms for both dry and wet samples were measured under hydrate favorable conditions. Hydrate in-situ formation loaded by the composite material was also carried out, while hydrate kinetics was evaluated by Raman spectrum. It was found that MIL-101(Cr) remains cubic symmetric structure when activated carbon (AC) was doped, but its size decreases with the increase in AC doping amount, while the specific surface area and pore volume significantly increase, and this enhances methane adsorption that increases by 65.58%. More enhanced methane uptake was obtained when wet sample was applied due to adsorption and hydration synergy, wherein methane physical adsorption ability remains, while formed hydrate stores extra methane. The contribution of hydrate to methane uptake is up to 40%, so large methane storage density is anticipated, methane volumetric uptake is up to 179.3 V/V under a mild condition (9.3 MPa and 274.15 K), which increases by 38.03%. Compared with our recently reported ZIF-8@AC, methane storage capacity in this new material increases by 36.5% (Chem. Eng. J., 2023, 455, 140503). In addition, hydrate progressive growth with the increase in adsorption pressure was observed, the area ratio of hydrate large cages to small one finally approaches to the theoretical value of 3:1, suggesting approximately complete conversion of pre-adsorbed water.

New material: Metal-organic frameworks for natural gas storage

As gasoline is a non-renewable source, scientists are continuing to find new sources which could replace the role of gasoline that are much cleaner and environmentally friendly. Natural gas is a good opinion as it reduces the amount of SOx, COx, and NOx being emitted and costs less compared to gasoline. The problems come as the volumetric energy density is much lower than expected. Scientists suggested three ways to overcome this challenge: CNG (Compressed natural gas), LNG (liquefied natural gas), and ANG (adsorbed natural gas). Metal-organic frameworks have been introduced for natural gas storage. The advantages and disadvantages of ANG using metal-organic frameworks (MOFs) have been discussed in detail. The quantification factors, such as gravimetric and volumetric uptake, adsorption conditions, thermal properties, and isosteric heat of adsorption usable methane capacity and morphology, are also mentioned for methane storage. Different metal-organic frameworks are compared to find the best material for methane storage. Considering all these quantification factors above between different MOFs, PCN-14 is the best MOF and has been widely used worldwide for methane storage. The paper hopes to provide state-of-the-art opinions regarding the application of MOFs in methane storage and facilitates the future of renewable energy usage.

A squarate-pillared titanium oxide quantum sieve towards practical hydrogen isotope separation

Separating deuterium from hydrogen isotope mixtures is of vital importance to develop nuclear energy industry, as well as other isotope-related advanced technologies. As one of the most promising alternatives to conventional techniques for deuterium purification, kinetic quantum sieving using porous materials has shown a great potential to address this challenging objective. From the knowledge gained in this field; it becomes clear that a quantum sieve encompassing a wide range of practical features in addition to its separation performance is highly demanded to approach the industrial level. Here, the rational design of an ultra-microporous squarate pillared titanium oxide hybrid framework has been achieved, of which we report the comprehensive assessment towards practical deuterium separation. The material not only displays a good performance combining high selectivity and volumetric uptake, reversible adsorption-desorption cycles, and facile regeneration in adsorptive sieving of deuterium, but also features a cost-effective green scalable synthesis using chemical feedstock, and a good stability (thermal, chemical, mechanical and radiolytic) under various working conditions. Our findings provide an overall assessment of the material for hydrogen isotope purification and the results represent a step forward towards next generation practical materials for quantum sieving of important gas isotopes.

Improved thermal management in HKUST-1 composites upon graphite flakes incorporation: Hydrogen adsorption properties

HKUST-1-based composites have been synthesized through the incorporation of synthetic graphite flakes in the MOF synthesis media. The presence of flakes gives rise to high quality HKUST-1 crystals, combining different morphologies (octahedral-shape crystals, cauliflower-shape crystals and truncated pyramids). The incorporation of graphite in the composites improves the structural stability of the embedded nanocrystals upon a conforming step at 377 kg/cm2 (0.5 tons), with limited structural damage (below 10% BET surface area reduction as compared to the 40% observed for pure HKUST-1). Furthermore, composites exhibit a significant improvement in thermal management, associated with the excellent thermal and electrical properties of the graphite microdomains incorporated. The improved stability of the composites is also reflected in the adsorption performance for hydrogen at atmospheric pressure and cryogenic temperatures, with a significant preservation of the adsorption properties (gravimetric capacity, <15% decrease vs powders) in the monoliths containing graphite. The best adsorption performance is achieved with sample HKUST-1@10GF, in monolithic form, with a volumetric excess uptake at 0.1 MPa and −195 °C close to 18.7 g/L. This value is among the best described in the literature for monolithic MOFs under similar adsorption conditions.

Development of novel ionic liquid-based silica gel composite adsorbents for designing high-efficiency adsorption heat pumps

Adsorption Cooling Systems ADCS as a thermally-driven technology provide an environmentally benign solution to supply cooling needs and utilize low-temperature heat sources. Adsorbent materials are the key element in the cooling performance of the ADCS. Poor heat transfer and low packing density are the main drawbacks of the conventional adsorbents, such as silica gel, that hinder the ADCS performance. Consolidated composite adsorbents represent a great solution for this problem, in which the binder material plays a significant role in the composite adsorbent synthesis and performance. In this paper, composite adsorbent based on RD Silica Gel SG as parent material and amino acid-based Polymerized Ionic Liquid PIL as a binder material, is synthesized at different PIL percentages, namely 2%, 5%, and 10%. The thermal and adsorption characteristics of the developed composite adsorbents in addition to the theoretical cooling performance ADCS with water adsorbate have been investigated. The results show that the thermal diffusivity has been improved by a maximum value of 20% for Composite 3, while the average volumetric water uptake has been enhanced for Composite 1 by a maximum value of 20.6%, compared to the parent silica gel.