Structure and thermodynamics of water adsorption in NU- 1500-Cr

Ho, Ching‐Hwa; Valentine, Mason L.; Chen, Zhijie; Xie, Haomiao; Farha, Omar K.; Xiong, Wei; Paesani, Francesco

doi:10.26434/chemrxiv-2023-tg7fs

Cited by 7 publications

(11 citation statements)

References 20 publications

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“…They also display much reduced intensities at higher q tet values. Similar behavior was seen in the NU-1500-Cr MOF 70 for water loadings prior to the isotherm step. In NU-1500-Cr, hydration was seen to begin with the saturation of the open Cr 3+ sites and proceeded with the formation of water chains (along the channels connecting the hexagonal pore).…”

Section: Pore-filling Mechanismsupporting

confidence: 70%

Insights into Isotherm Step and Pore-Filling Mechanisms for Water Adsorption in Covalent Organic Frameworks

Brahma,

Dwarkanath,

Balasubramanian

2024

Chem. Mater.

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Atmospheric water harvest using porous materials is an attractive solution to the water crisis. The inflection point (α) in the water adsorption isotherm is one of the crucial criteria to screen porous materials for their water-harvesting properties. Here, we propose a simulation protocol that can help predict α in covalent organic frameworks (COFs) via an implementation of the flat histogram atomistic Monte Carlo simulation method, NVT + W, with interpolation. The step positions for six COFs possessing diverse linkages and varied hydrophilicity as calculated from the simulations matched well with those from experiments. The simulations revealed two distinct types of pore-filling mechanisms in these COFs at water loadings before the inflection point that depended on both the binding strength and the number of hydrophilic binding sites. The work paves the way to use these structural attributes as descriptors which can be deployed for the large-scale screening of COFs as potential water harvesters.

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Section: Pore-filling Mechanismsupporting

confidence: 70%

Insights into Isotherm Step and Pore-Filling Mechanisms for Water Adsorption in Covalent Organic Frameworks

Brahma,

Dwarkanath,

Balasubramanian

2024

Chem. Mater.

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“…82,83,[105][106][107] Additionally, MB-pol has been successfully used to characterize the behavior of water within various MOFs. [85][86][87][88]90 Water-framework interactions were represented by electrostatic and van der Waals terms. The electrostatic term of MB-pol includes both permanent and induced (i.e., polarization) contributions, which implies that in the MD simulations each MB-pol water molecule could be polarized by other MB-pol water molecules as well as the framework, while the framework was not polarizable.…”

Section: A Force Fieldmentioning

confidence: 99%

Molecular driving forces for water adsorption in MOF-808: A comparative analysis with UiO-66

Frank,

Paesani

2023

Preprint

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Metal-organic frameworks (MOFs), with their unique porous structures and versatile functionality, have emerged as promising materials for adsorption, separation, and storage of diverse molecular species. In this study, we investigate water adsorption in MOF-808, a prototypical MOF that shares the same secondary building unit (SBU) as UiO-66, and elucidate how differences in topology and connectivity between the two MOFs influence the adsorption mechanism. To this end, molecular dynamics (MD) simulations were performed to calculate several thermodynamic and dynam- ical properties of water in MOF-808 as a function of relative humidity (RH), from the initial adsorption step to full pore filling. At low RH, the μ3-OH groups of the SBUs form hydrogen bonds with the initial water molecules entering the pores, which triggers the filling of these pores before the μ3-OH groups in other pores become en- gaged in hydrogen bonding with water molecules. Our analyses indicate that the pores of MOF-808 become filled by water sequentially as the RH increases. A similar mechanism has been reported for water adsorption in UiO-66, a MOF that shares the same SBU with MOF-808. Despite this similarity, our study highlights distinct ther- modynamic properties and framework characteristics that influence the adsorption process differently in MOF-808 and UiO-66.

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“…Remarkably, this behavior diverges from that observed for NU-1500-Cr (a framework previously studied by the same methods), in which the entropy rapidly decreases during capillary condensation. 25 This difference can be ascribed to the characteristics of the primary interaction sites during the initial hydration phase, resulting in distinct dynamic properties of water molecules, which will be further elaborated in the subsequent section.…”

Section: ■ Introductionmentioning

confidence: 99%

Cooperative Interactions with Water Drive Hysteresis in a Hydrophilic Metal–Organic Framework

Oppenheim,

Ho,

Alezi

et al. 2024

Chem. Mater.

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Devices that utilize the reversible capture of water vapor provide solutions to water insecurity, increasing energy demand, and sustainability. In all of these applications, it is important to minimize water adsorption–desorption hysteresis. Hysteresis is particularly difficult to avoid for sorbents that bind water strongly, such as those that take up below 10% relative humidity (RH). Even though the theoretical factors that affect hysteresis are understood, understanding the structure–function correlations that dictate the hysteretic behavior in water sorbents remains a challenge. Herein, we synthesize a new hexagonal microporous framework, Ni2Cl2BBTQ (H2BBTQ = 2H,6H-benzo[1,2-d][4,5-d′]bistriazolequinone), to elucidate these principles. Uniquely among its known isoreticular analogues, Ni2Cl2BBTQ presents unusually high hysteresis caused by strong wetting seeded by a particularly strong zero-coverage interaction with water. A combination of vibrational spectroscopies and detailed molecular dynamics simulations reveals that this hysteretic behavior is the result of an intricate hydrogen-bonding network, in which the monolayer consists of water simultaneously binding to open nickel sites and hydrogen bonding to quinone sites. This latter hydrogen-bonding interaction does not exist in other isoreticular analogues: it prevents facile water dynamics and drives hysteresis. Our results highlight an important design criterion for water sorbents: in order to drive water uptake in progressively dry conditions, the common strategy of increasing hydrophilicity can cause strong wetting and the formation of superclusters, which lead to undesirable hysteresis. Instead, hysteresis-free water uptake at extremely low humidity is best promoted by decreasing the pore size, rather than increasing hydrophilicity.

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Structure and thermodynamics of water adsorption in NU- 1500-Cr

Cited by 7 publications

References 20 publications

Insights into Isotherm Step and Pore-Filling Mechanisms for Water Adsorption in Covalent Organic Frameworks

Insights into Isotherm Step and Pore-Filling Mechanisms for Water Adsorption in Covalent Organic Frameworks

Molecular driving forces for water adsorption in MOF-808: A comparative analysis with UiO-66

Cooperative Interactions with Water Drive Hysteresis in a Hydrophilic Metal–Organic Framework

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