Water Adsorption Research Articles

Hydrophobic post-functionalization of a water instable bioMOF: Effect on CO2 and water adsorption

Hydrophobic post-functionalization of a water instable bioMOF: Effect on CO2 and water adsorption

Evaluation of the onset voltage of water adsorption on Pt(111) surface using density functional theory/implicit model calculations

Evaluation of the onset voltage of water adsorption on Pt(111) surface using density functional theory/implicit model calculations

Amplifying Electron-Donor Signal of the "Water Gate" Enabled Low Detection Ability of a Field-Effect Transistor-Based Humidity Sensor.

Low humidity detection down to the parts per million level is urgently demanded in various industrial applications. The hardly detected tiny electrical signal variations caused by a very small amount of water adsorption are one of the intrinsic reasons that restrain the detection limit of the humidity sensors. Herein, a carbon-based field-effect transistor (FET) humidity sensor utilizing adsorbed water as the dual function of a sensing gate and analyte was proposed. Owing to the electron donor property of the "water gate" that can serve as a negative voltage exerted on the dielectric layer, the electrical conductivity of the FET's channel can be significantly modulated, therefore realizing signal amplification. The proposed sensor presents a detection limit of lower than 1% RH. Besides, the fabricated sensors show good batch consistency (response deviation of 0.5%), repeatability, long-term stability, and acceptable hysteresis (6.3% relative humidity (RH)) in humidity detection. We hope that our work can offer a novel strategy for the application and integration of low humidity detection from the device aspect rather than sensing materials synthesis.

Physically cross-linked cellulose nanofiber (LCNF/CNF) hydrogels: impact of the composition on mechanical and swelling properties

Lignocellulose nanofibers (LCNFs) are highly regarded for their ability to significantly enhance the rigidity of formed structures. When integrated into cellulose nanofiber (CNF) hydrogels, they hold substantial promise in augmenting mechanical strength, as well as improving adsorption capacity. Herein, the preparation of hydrogels from an aqueous suspension of CNFs and LCNFs extracted from eucalyptus cellulose pulp through a homogenization process is outlined. Suspensions of different concentrations were prepared to assess the influence of lignin and nanofiber content on the properties of the hydrogels. The hydrogels cellulose nanofibers (HCNF) and lignocellulose nanofibers (HLCNF) were formed through a freeze–thaw process, revealing an enhancement in rigidity with increasing nanofiber concentration. DFT (density functional theory) calculations illustrated the cross-linking mechanism between cellulose chains induced by the crystallization of water molecules, thus, corroborating the postulated hydrogel formation mechanism. Microstructural analysis revealed honeycomb-shaped matrices in longitudinal sections, with HLCNF hydrogels presenting less smooth walls. Studies on water adsorption capacity showed rapid swelling in both hydrogels, correlated with the nanofiber content reaching 8750% and 5500% for HLCNF and HCNF, respectively. HLCNF hydrogels exhibited higher adsorption capacity due to the influence of lignin on cross-linking rates. Mechanical compression tests demonstrated exceptional resilience in all hydrogels. Despite having a lower cross-linking density compared to hydrogels made from 2 wt.% cellulose nanofibers, hydrogels composed of 2 wt.% lignocellulose nanofibers exhibited a Young’s modulus of 2.83 kPa. This underscores the superior mechanical properties of lignin-based hydrogels, highlighting the effect of lignin on the hydrogel matrix.

Creating Dual Active Sites in Ru-doped FeMn-MOF-74 for Efficient Overall Water Splitting.

The design of well-engineered bifunctional electrocatalysts is crucial for achieving durable and efficient performance in overall water splitting. In this study, Ru-doped FeMn-MOF-74 itself has Ru sites and generates FeMnOOH under catalytic conditions, forming dual active sites for overall water splitting. Density functional theory (DFT) calculations demonstrate that the Ru dopants exhibit optimized binding strength for H* and enhanced hydrogen evolution reaction (HER) performance. Moreover, the Mn sites within FeMnOOH lower the energy barrier for the rate-determining step (from O* to OOH*), serving as the active centre for oxygen evolution reaction (OER). The incorporation of Ru significantly improves the electron transfer properties of FeMn-MOF-74 and enhances its water adsorption capacity, synergistically boosting its bifunctional activity. This strategy of designing dual active sites provides new insights into the development of bifunctional metal-organic frameworks (MOFs) for efficient overall water splitting.

Separation of Ethanol–Water Azeotrope Using Waste Carrageenan Filter‐Cake Adsorbent

ABSTRACTThe final step in the downstream processing of bioethanol is typically the removal of water from the ethanol–water azeotrope (95.6 wt.% ethanol) to obtain fuel‐grade ethanol (> 99 wt.%). This can be done by various techniques including distillation (azeotropic or extractive), membrane‐based separation, and adsorption using molecular sieves or bio‐based adsorbents. In this work, a waste by‐product of carrageenan production is studied for its efficacy as water adsorbent. This waste carrageenan filter‐cake (CFC) material is primarily composed of organics (22 wt.% cellulose and carrageenan) and ash (78 wt.% perlite) as inferred from the proximate analysis. The functional groups present in the material were identified by FTIR analyses, and the surface morphology was checked by FESEM. Liquid phase water adsorption isotherms at 30°C, 40°C, and 50°C were established and were found to be adequately described by both Langmuir (R2 = 0.93 to 0.97) and Brouers‐Sotolongo (R2 = 0.96 to 0.97) models. An enthalpy change of adsorption of about −17 kJ/mol was computed through the van't Hoff equation. An azeotropic mixture (95.6 wt.% ethanol) was successfully purified to above 99.2 wt.% ethanol in a CFC‐packed column. The CFC adsorbent was used in three adsorption–desorption cycles without much loss in capacity. Moreover, the Thomas model adequately described the breakthrough curves.

Theoretical Insights into Methanol Electro-Oxidation on NiPd Nanoelectrocatalysts: Investigating the Carbonate–Palladium Oxide Pathway and the Role of Water and OH Adsorption

We conducted a theoretical and experimental study on the electro-oxidation of methanol (MOR) on NixPdy nanoparticles. The results are presented in terms of kinetic parameters, surface concentrations, and peak currents, showing significant differences between three main compositions: Ni3Pd1, Ni1Pd1, and Ni1Pd3. The kinetic mechanism adopted for accounting the linear voltammetry experiments performed follows the carbonate–palladium oxide pathway of the MOR. Numerical simulations of the kinetic equations, fitted to experimental data obtained at varying methanol concentrations, allowed us to distinguish the adsorption contributions of methanol, water, and OH ions from the nonlinear contribution associated with palladium oxide and carbon dioxide production. The synergistic effects of Ni:Pd nanoalloys on the MOR were then assessed by analyzing the behavior and tendencies of the reaction rate constants for different bulk methanol concentrations. Our results suggest that a higher Pd content favors more efficient oxidation mechanisms by reducing the formation of intermediate products that cause surface poisoning, such as CO, carbonates, or palladium oxide. However, as the proportion of Ni increases, an increase in the concentration of adsorbed OH is observed, which dominates the blocking of active sites even greater than the palladium oxide blocking.

Hydrogen Spillover Enabled by Edge Dislocations for Efficient Hydrogen Evolution

AbstractDesigning an efficient alkaline hydrogen evolution reaction (HER) catalyst requires enhanced hydrogen adsorption to facilitate water dissociation while noting that this would be detrimental to H2 desorption. Although hydrogen spillover‐assisted HER has been emerging as a promising strategy due to separated active sites for water dissociation and hydrogen formation enabled by heterogeneous catalysts, interfacial charge accumulation, and strong interfacial proton adsorption would hinder proton transfer due to a high energy barrier. Herein, a novel strategy to realize hydrogen spillover‐assisted HER enabled by edge dislocations of Mo2C catalyst is presented. The coupled tensile‐compressive strain regions induced by edge dislocations serve as nano‐reactors for HER. The Volmer process is greatly enhanced by strong water adsorption and efficient *H2O dissociation in the tensile regions, meantime the generated *H rapidly transfers to the compressive regions for easy hydrogen molecule release. As a result, the edge dislocation‐rich catalyst achieves a low overpotential of only 61 and 179 mV at 10 and 300 mA cm−2, showcasing a new way to apply hydrogen spillover in single‐phase catalysts and offering potential for developing cost‐effective and efficient HER catalysts.

Amine-functionalizedTriazolate-basedMetal-Organic Frameworks for Enhanced Diluted CO2 Capture Performance.

Efficient CO2 capture at concentrations between 400-2000 ppm is essential for maintaining air quality in a habitable environment and advancing carbon capture technologies. This study introduces NICS-24 (National Institute of Chemistry Structures No. 24), a Zn-oxalate 3,5-diamino-1,2,4-triazolate framework with two distinct square-shaped channels, designed to enhance CO2 capture at indoor-relevant concentrations. NICS-24 exhibits a CO2 uptake of 0.7 mmol/g at 2 mbar and 25 °C, significantly outperforming the compositionally related Zn-oxalate 1,2,4-triazolate - CALF-20 (0.17 mmol/g). Improved performance is attributed to amino-functions that enhance CO2 binding and enable superior selectivity over N2 and O2, achieving 8-fold and 30-fold improvements, respectively, in simulated CO2/N2 and CO2/O2 atmospheric ratios. In humid environments, NICS-24 retained structural integrity but exhibited an 85 % reduction in CO2 capacity due to competitive water adsorption. Breakthrough sorption experiments, atomistic NMR analysis, and DFT calculations revealed that water preferentially adsorbs over CO2 due to strong hydrogen-bonding interactions within the framework. Gained understanding of the interaction between CO2 and H2O within the MOF framework could guide the modification via rational design with improved performance under real-world conditions.

Ab Initio Predictions of Adsorption in Flexible Metal-Organic Frameworks for Water Harvesting Applications.

Metal-organic frameworks such as MOF-303 and MOF-LA2-1 have demonstrated exceptional performance for water harvesting applications. To enable a reticular design of such materials, an accurate prediction of the adsorption properties with chemical accuracy and fully accounting for the flexibility is crucial. The computational prediction of water adsorption properties in MOFs has become standard practice, but current methods lack the predictive power needed to design new materials. Limitations stem from the way the interatomic potential is described and the inadequate consideration of the framework flexibility. Herein, we showcase a methodology to obtain chemically accurate adsorption isotherms that fully account for framework flexibility. The method relies on very accurate and efficiently trained machine learning potentials and transition matrix Monte Carlo simulations to account for framework flexibility. For MOF-303, quantitatively accurate adsorption isotherms are obtained, provided an accurately benchmarked electronic structure method is used to train the machine learning potential, and local and global framework flexibility is accounted for. The broader applicability is shown through the study of MOF-333 and MOF-LA2-1. Analysis of the water density profiles in the MOFs gives insight into the factors governing the shape and origin of the isotherm. An optimal water harvester should have initial seeding sites with intermediate adsorption strength to prevent detrimental low-pressure water uptake. To increase the working capacity, linker extension strategies can be used while maintaining the initial seeding sites, as was done in MOF-LA2-1. The methodology can be applied to other guest molecules and MOFs, enabling the future design of MOFs with specific adsorption properties.

Disordered gold nanoislands-dielectric-metal plasmon reflector for polarization-sensitive color display, humidity sensor and optical memory.

The interaction between ultrafast, tightly focused lasers and materials has garnered significant interest owing to its distinctive properties. In this study, we present a versatile methodology for the fabrication of tunable plasmonic nanostructures by employing a disordered gold nanoisland-dielectric-metal configuration, achieved through femtosecond laser printing. By reshaping the gold nanoislands and reconfiguring them into nanograting-like structures, the orientation of these nanostructures is influenced by the polarization of the femtosecond laser light, leading to controllable plasmon resonance and polarization-sensitive color display. Furthermore, the system demonstrates a significant sensitivity to environmental humidity, as indicated by water adsorption, which leads to marked color changes. The hotspots generated through plasmonic coupling among disordered gold nanoislands significantly enhance polarization-multiplexed optical data storage, characterized by its high quality and low energy consumption. This experimental demonstration promotes the advancement of sophisticated optical devices for plasmonic color printing with tailored characteristics, thereby offering economical solutions for applications in optoelectronics and sensing.

Metal-Organic Framework-Assisted Atmospheric Water Harvesting Enables Cheap Clean Water Available in an Arid Climate: A Perspective.

Extracting water directly from the atmosphere seems to be a perfect way to solve the water scarcity facing 2 billion people; however, traditional Atmospheric Water Harvesting (AWH) lacks the ability to adsorb water molecules in an arid climate. Porous materials are capable of assisting water adsorption; however, currently, only certain customizable Metal-Organic Frameworks (MOFs) are able to meet the standard of adsorbing water molecules at low humidity and releasing water at low temperatures at certain times that can realize assisted AWH's practical and energy-efficient use (Energy consumption < 5kWh/L-water). From this perspective, we offer a concise review of the advancements in enhanced AWH technologies, delve into the attributes of appropriate MOFs, and offer insights into the potential and future directions of MOFs-AWH. In conclusion, we underscore that that the development of designable MOFs holds the key to the widespread practical implementation of AWH, promising the availability of affordable clean water anywhere in the world.

Modeling ethanol/water adsorption in all-silica zeolites using the real adsorbed solution theory.

A comprehensive set of single-component and binary isotherms were collected for ethanol/water adsorption into the siliceous forms of 185 known zeolites using grand-canonical Monte Carlo simulations. Using these data, a systematic analysis of ideal/real adsorbed-solution theory (IAST/RAST) was conducted and activity coefficients were derived for ethanol/water mixtures adsorbed in different zeolites based on RAST. It was found that activity coefficients of ethanol are close to unity while activity coefficients of water are larger in most zeolites, indicating a positive excess free energy of the mixture. This observation can be attributed to water/ethanol interactions being less favorable than water/water interactions in the single-component adsorption of water at comparable loadings. The deviation from ideal behavior can be highly structure-dependent but no clear correlation with pore diameters was identified. Our analysis also demonstrates the following: (1) accurate unary isotherms in the low-loading regime are critical for obtaining physically sensible activity coefficients; (2) the global regression scheme to solve for activity model parameters performs better than fitting activity models to activity coefficients calculated locally at each binary state point; and (3) including the dependence on adsorption potential offers only a minor benefit for describing binary adsorption at the lowest fugacities. Finally, the Margules activity model was found incapable of capturing the non-ideal adsorption behavior over the entire range of fugacities and compositions in all zeolites, but for conditions typical of solution-phase adsorption, RAST predictions using zeolite-specific or even bulk Margules parameters provide an improved description compared to IAST.

Methanol-Enhanced Low-Cell-Voltage Hydrogen Generation at Industrial-Grade Current Density by Triadic Active Sites of Pt1-Pdn-(Ni,Co)(OH)x.

Methanol (ME) is a liquid hydrogen carrier, ideal for on-site-on-demand H2 generation, avoiding its costly and risky distribution issues, but this "ME-to-H2" electric conversion suffers from high voltage (energy consumption) and competitive oxygen evolution reaction. Herein, we demonstrate that a synergistic cofunctional Pt1Pdn/(Ni,Co)(OH)x catalyst with Pt single atoms (Pt1) and Pd nanoclusters (Pdn) anchored on OH-vacancy(VOH)-rich (Ni,Co)(OH)x nanoparticles create synergistic triadic active sites, allowing for methanol-enhanced low-voltage H2 generation. For MOR, OH* is preferentially adsorbed on Pdn and then interacts with the intermediates (such as *CHO or *CHOOH) adsorbed favorably on neighboring Pt1 with the assistance of hydrogen bonding from the surface hydrogen of (Ni,Co)(OH)x. The enhanced selectivity of the *CHOOH pathway, instead of *CO, sustains the MOR activity to a practically high current density. For HER, triadic Pt1, Pdn, and OH-vacancy sites on (Ni,Co)(OH)x create an "acid-base" microenvironment to facilitate water adsorption and splitting, forming H* species on Pt1 and Pdn, and *OH at the vacancy, to promote efficient H2 evolution from the asymmetric Pt1 and Pdn sites via the Tafel mechanism. The triadic-site synergy opens new avenues for the design and synthesis of highly efficient and stable cofunctional catalysts for "on-site-on-demand" H2 production, here facilitated by liquid methanol.

All‐Polymer Solid Desiccant With High Moisture Capture Capacity and Fast Sorption Kinetics

ABSTRACTDesiccants play crucial importance in both daily life and industrial production. The development of low‐cost and easy industrial scale production all‐polymer solid desiccants with high water adsorption capacity, low regeneration temperature, and fast sorption kinetics remains great challenges. Herein, we report a novel all‐polymer porous solid desiccant (APPSD) with high moisture capture capacity, low regeneration temperature, and fast sorption kinetics via a new zero‐waste, eco‐friendly, and easily scaled‐up process. The present APPSD could adsorb 0.8 g/g water vapor at 70% relative humidity (RH) within 1.5 h, and 1.9 g/g at 90% RH within 2.0 h at 25°C, exhibiting fast adsorption kinetics. The equilibrium moisture adsorptive capacity is as high as 2.16 g/g at 90% RH and 25°C, much higher than most reported solid polymer desiccants without hygroscopic salts under the same conditions. Amazingly, more than 92% of the absorbed water could be released at 40°C and 20% RH within 30 min, demonstrating extreme low regeneration temperature and high regeneration efficiency. Furthermore, almost no performance decline was observed during a 20‐cycle adsorption–desorption measurement, showing excellent recycling stability.

Involving degradation products provides a new perspective of diffuse pollution assessment of atrazine with a modified mass balance approach.

Atrazine (ATR) is an endocrine disruptor known for its persistence and mobility. While the diffuse characteristics and potential risks of ATR have been extensively studied, its transregional migration and degradation characteristics have received less attention. In this study, a modified mass balance approach considering the diffuse source (DS), tributaries, water resource usage, degradation, adsorption, and evaporation was developed based on the traditional mass balance framework and field sampling to estimate the DS fluxes of ATR in a large river basin. Field sampling revealed that the ATR concentration in the surface water increased downstream, whereas the ATR levels in suspended particulate matter decreased. The ATR degradation ratio also decreased downstream, suggesting increased input along the river. The modified mass balance approach identified DS as the primary ATR source in the river, followed by tributaries. Together, the DS input and tributary inflow accounted for 95.6 % ± 2.1 % of the total ATR flux, with DS alone contributing 73.8 % ± 10.2 %. Finally, the ATR parent and its hazardous materials (ATR, desethylatrazine, and desisopropylatrazine) accounted for 6 % and 27 %, respectively, of the total ATR content that reached the estuary. This integrated consideration of ATR and its degradation products offer a new perspective on their transregional migration and degradation patterns resulting from diffuse pollution.

Fish scale gelatin/diatom biosilica composite hemostasis sponge with ultrafast dispersing and in situ gelation for hemorrhage control.

Rapid control of hemorrhage is vital in first-aid and surgery. As representative of emergency hemostatic materials, inorganic porous materials achieve rapid hemostasis through concentrating protein coagulation factors by water adsorption to accelerate the coagulation reaction process, however their efficacy is often limited by the insufficient contact of material with blood and the lack of blood clot strength. Herein, we report an ultrafast dispersing and in situ gelation sponge (SG/DB) based on anchoring interface effect for hemorrhage control using freeze drying method after mixing fish scale gel (SG) and tert-butyl alcohol (TBA) pre-crystallized diatom biosilica (DB). This design retains the hierarchical porous structure of DB in SG matrix, and granting the SG/DB the capability to disperse ultrafast, achieving dissolution in both water and blood within 3 s. The DB and SG released by disintegration of SG/DB can activate intrinsic coagulation pathway and strengthen fibrin clot gelation through the anchoring interface effect, even realizing coagulation of anticoagulant whole blood without calcium ion activation. Animal studies showed 10%T-SG/DB has superior hemostatic properties to various commercially available hemostatic materials (rat liver and artery, 100 s; rabbit liver, artery, and heart, 3.2, 4.6, and 2.9 min, respectively), reducing bleeding by 30 % compared to QuikClot Combat Gauze®, and is easily removable without residue.

Adsorption Structure and Selectivity of Phenols in Water-Immersed Organomontmorillonite Investigated by Molecular Simulation.

The two-dimensional interlayer space of layered materials has been highlighted due to their adsorption property, whose nanostructure in the water-immersed state is scarcely understood by experiment. Recent developments in molecular simulation have enabled researchers to investigate the interlayer structure, but water content is necessary for accurate modeling. In the present study, we proposed a theoretical method to estimate the saturated water content and adsorption selectivity of trichlorophenol and phenol in montmorillonite modified with hexadecyltrimethylammonium ions. By analyzing non-bond energy in interlayer water and following comparison with the bulk water model, the saturated water content was estimated to be between 12.7 and 14.2 wt %, which is consistent with the corresponding thermogravimetry data. In the water-immersed state, trichlorophenol was distributed in the center of the interlayer due to the van der Waals interaction with the organocation. Solvation free energy analysis revealed that trichlorophenol was more stable in the interlayer than in the aqueous solution, while the opposite result was obtained for phenol, reproducing the adsorption selectivity reported experimentally. Thus, it was found that both the saturated water content and adsorption selectivity are predicted by molecular simulation. The adsorption site of trichlorophenol changed from the center of the interlayer to the clay surface in the dry state, indicating that accurate modeling in the water-immersed state is significant for revealing the adsorption structure.

Stable Antifouling and Antibacterial Coating Based on Assembly of Copper-Phenolic Networks.

Biofilm formation on medical devices has become a worldwide issue arising from its resistance to bactericidal agents and presenting challenges to eradicating biofouling adhesion, especially in biological fluids. Metal-phenolic networks have been demonstrated as a versatile and efficient strategy to prevent biofilm formation by endowing medical devices with prolonged antifouling and antibacterial activities in a one-step surface modification. In this study, we report a simple and environmentally friendly method using coordination chemistry between copper ions (Cu2+) and dopamine-containing copolymer to fabricate metal-phenolic network-based coatings. The phenolic groups also imparted the adhesion of glycopolymer-containing dopamine residues to inorganic and organic substrates, resulting in dual antifouling and bactericidal surfaces. 2-gluconamidoethyl methacrylamide monomer (GAEMA) was first copolymerized with dopamine methacrylamide (DMA) using a free-radical polymerization process. The resulting copolymer (GAEMA-DMA), denoted as GADMA, was then mixed with copper ions in a one-step process to form the GADMA-Cu coating. The GADMA-Cu coating was hydrophilic and significantly reduced the water contact angle (WCA) and adsorption of bovine serum albumin protein even after incubation in a bovine serum albumin solution for 30 h. Moreover, the coating exhibited strong antibacterial activity against Escherichia coli and Staphylococcus aureus and was biocompatible with 99% cell viability toward normal human fibroblast (HDFa) cells. Thus, our coating shows great potential for application in medical devices.

Face-controlled chirality induction in octahedral thiacalixarene-based porous coordination cages.

Nanosized chiral octahedral M32 coordination cages were prepared via self-assembly of sulfonylcalix[4]arene tetranuclear M(II) clusters (M = Co or Ni) with enantiomerically enriched linkers based on tris(dipyrrinato)cobalt(III) complexes, appended with peripheral carboxylic groups. Two pairs of enantiomers of cages were obtained and unambiguously characterized from a structural point of view, using single crystal X-ray diffraction. Chiral-HPLC was used to evidence the enantiomers. In the solid state, the compounds present intrinsic and extrinsic porosity: the intrinsic porosity is linked with the size of the cages, which present an inner diameter of ca. 19 Å. The obtained solid-state supramolecular architectures demonstrated good performances as adsorbents for water and 2-butanol guest molecules.