scholarly journals Water Capture Mechanisms at Zeolitic Imidazolate Framework Interfaces

2021 ◽  
Author(s):  
Jackson Wagner ◽  
Kelly Hunter ◽  
Francesco Paesani ◽  
Wei Xiong
Keyword(s):  
Md Simulations ◽  
Relative Strength ◽  
Pore Filling ◽  
Zeolitic Imidazolate Framework ◽  
Sum Frequency ◽  
Spectral Lineshape ◽  
Sum Frequency Generation Spectroscopy ◽  
Metal Organic ◽  
Water Filling ◽  
Humidity Dependence

Water capture mechanisms of zeolitic imidazolate framework ZIF-90 are revealed by differentiating the water clustering and the center pore filling step, using vibrational sum-frequency generation spectroscopy (VSFG) at a one-micron spatial resolution and state-of-the-art molecular dynamics (MD) simulations. Through spectral lineshape comparison between VSFG and IR spectra, the relative humidity dependence of VSFG intensity, and MD simulations, based on MB-pol, we found water clustering and center pore filling happen nearly simultaneously within each pore, with water filling the other pores sequentially. The integration of nonlinear optics with MD simulations provides critical mechanistic insights into the pore filling mechanism and suggests that the relative strength of the hydrogen bonds governs the water uptake mechanisms. This molecular-level detailed mechanism can inform the rational optimization of metal-organic frameworks for water harvesting.

scholarly journals Water Capture Mechanisms at Zeolitic Imidazolate Framework Interfaces

2021 ◽  
Author(s):  
Jackson Wagner ◽  
Kelly Hunter ◽  
Francesco Paesani ◽  
Wei Xiong
Keyword(s):  
Rational Design ◽  
Md Simulations ◽  
Pore Filling ◽  
Zeolitic Imidazolate Framework ◽  
Initial Water ◽  
Sum Frequency ◽  
Hydrogen Bond Interactions ◽  
Sum Frequency Generation Spectroscopy ◽  
Water Filling ◽  
Filling Mechanism

Water capture mechanisms of zeolitic imidazolate framework ZIF-90 are revealed by differentiating the water clustering at interior interfaces of ZIF-90 and the center pore filling step, using vibrational sum-frequency generation spectroscopy (VSFG) at a one-micron spatial resolution. Spectral lineshapes of VSFG and IR spectra suggest that OD modes of heavy water in both water clustering and center pore filling steps experience similar environments, which is unexpected as weaker hydrogen bond interactions are involved in initial water clustering at interior surfaces. VSFG intensity shows similar dependence on the relative humidity as the adsorption isotherm, suggesting that water clustering and pore filling occur simultaneously. MD simulations based on MB-pol corroborate the experimental observations, indicating that water clustering and center pore filling happen nearly simultaneously within each pore, with water filling the other pores sequentially. The integration of nonlinear optics with computational simulations provides critical mechanistic insights into the pore filling mechanism that could be applied to the rational design of future MOFs.

scholarly journals Water Capture Mechanisms at Zeolitic Imidazolate Framework Interfaces

2021 ◽  
Author(s):  
Jackson Wagner ◽  
Kelly Hunter ◽  
Francesco Paesani ◽  
Wei Xiong
Keyword(s):  
Rational Design ◽  
Md Simulations ◽  
Pore Filling ◽  
Zeolitic Imidazolate Framework ◽  
Initial Water ◽  
Sum Frequency ◽  
Hydrogen Bond Interactions ◽  
Sum Frequency Generation Spectroscopy ◽  
Water Filling ◽  
Filling Mechanism

Water capture mechanisms of zeolitic imidazolate framework ZIF-90 are revealed by differentiating the water clustering at interior interfaces of ZIF-90 and the center pore filling step, using vibrational sum-frequency generation spectroscopy (VSFG) at a one-micron spatial resolution. Spectral lineshapes of VSFG and IR spectra suggest that OD modes of heavy water in both water clustering and center pore filling steps experience similar environments, which is unexpected as weaker hydrogen bond interactions are involved in initial water clustering at interior surfaces. VSFG intensity shows similar dependence on the relative humidity as the adsorption isotherm, suggesting that water clustering and pore filling occur simultaneously. MD simulations based on MB-pol corroborate the experimental observations, indicating that water clustering and center pore filling happen nearly simultaneously within each pore, with water filling the other pores sequentially. The integration of nonlinear optics with computational simulations provides critical mechanistic insights into the pore filling mechanism that could be applied to the rational design of future MOFs.

scholarly journals Spectroscopic BIL-SFG Invariance Hides the Chaotropic Effect of Protons at the Air-Water Interface

Atmosphere ◽  
2018 ◽  
Vol 9 (10) ◽  
pp. 396 ◽  
Author(s):  
Simone Pezzotti ◽  
Marie-Pierre Gaigeot
Keyword(s):  
Water Structure ◽  
Md Simulations ◽  
Interfacial Structure ◽  
Water Interface ◽  
Sum Frequency ◽  
Hydronium Ion ◽  
Sum Frequency Generation Spectroscopy ◽  
Air Water Interface ◽  
Ph Conditions ◽  
Shed Light

The knowledge of the water structure at the interface with the air in acidic pH conditions is of utmost importance for chemistry in the atmosphere. We shed light on the acidic air-water (AW) interfacial structure by DFT-MD simulations of the interface containing one hydronium ion coupled with theoretical SFG (Sum Frequency Generation) spectroscopy. The interpretation of SFG spectra at charged interfaces requires a deconvolution of the signal into BIL (Binding Interfacial Layer) and DL (Diffuse Layer) SFG contributions, which is achieved here, and hence reveals that even though H 3 O + has a chaotropic effect on the BIL water structure (by weakening the 2D-HBond-Network observed at the neat air-water interface) it has no direct probing in SFG spectroscopy. The changes observed experimentally in the SFG of the acidic AW interface from the SFG at the neat AW are shown here to be solely due to the DL-SFG contribution to the spectroscopy. Such BIL-SFG and DL-SFG deconvolution rationalizes the experimental SFG data in the literature, while the hydronium chaotropic effect on the water 2D-HBond-Network in the BIL can be put in perspective of the decrease in surface tension at acidic AW interfaces.

scholarly journals Remedy for Collapse of ZIF Derived Carbon: Micro-Pore Filled Synthesis to Improve ORR Catalytic Property

2022 ◽  
Author(s):  
Xingxing Wu ◽  
Songwei Zhang ◽  
Jiaojiao Gao ◽  
Xiaopeng Liu ◽  
Qunhui Yuan ◽  
...  
Keyword(s):  
Active Sites ◽  
Metal Organic Framework ◽  
Reduction Reaction ◽  
High Nitrogen Content ◽  
High Nitrogen ◽  
Pore Filling ◽  
Zeolitic Imidazolate Framework ◽  
Half Wave ◽  
Metal Organic ◽  
Air Battery

Abstract Zeolitic imidazolate framework (ZIF) derived carbons deliver outstanding performance as oxygen reduction reaction (ORR) catalysts. However, their electrocatalytic activities are limited due to unavoidable collapse of ZIFs upon pyrolysis, which results in degradation of porosity, sintering of metals and loss of active sites. In this work, a micro-pore filling strategy was employed to strength the architecture of ZIF by using size matched cyanamide molecules as fillers. The cyanamide with high nitrogen content shows a triple effect in stabilizing the carbonaceous skeleton, preserving of metal containing active sites and improving the conductivity of matrix. Therefore, the as-prepared Fe, Co co-doped ZIF derived carbon (FeCo@NC-N) delivers a significantly improved electrochemical activity for ORR than its unfilled counterpart, with half-wave potential upshifted by 30 mV (0.84 V vs. RHE). Besides, a promoted power density of home-assembled zinc-air battery is obtained when FeCo@NC-N is applied as cathode catalyst. This work demonstrates a reliable approach to mitigate framework collapse of metal organic framework (MOF), thus may open a new way for fabrication of MOF based catalysts with increased loading of pores and active sites.

Temperature Dependence of the Air/Water Interface Revealed by Polarization Sensitive Sum-Frequency Generation Spectroscopy

2018 ◽  
Author(s):  
Daniel R. Moberg ◽  
Shelby C. Straight ◽  
Francesco Paesani
Keyword(s):  
Temperature Dependence ◽  
Low Frequency ◽  
Potential Energy Function ◽  
Md Simulations ◽  
Sum Frequency Generation ◽  
Water Molecules ◽  
Water Interface ◽  
Sum Frequency ◽  
Air Water Interface ◽  
Frequency Generation

<div> <div> <div> <p>The temperature dependence of the vibrational sum-frequency generation (vSFG) spectra of the the air/water interface is investigated using many-body molecular dynamics (MB-MD) simulations performed with the MB-pol potential energy function. The total vSFG spectra calculated for different polarization combinations are then analyzed in terms of molecular auto-correlation and cross-correlation contributions. To provide molecular-level insights into interfacial hydrogen-bonding topologies, which give rise to specific spectroscopic features, the vSFG spectra are further investigated by separating contributions associated with water molecules donating 0, 1, or 2 hydrogen bonds to neighboring water molecules. This analysis suggests that the low frequency shoulder of the free OH peak which appears at ∼3600 cm−1 is primarily due to intermolecular couplings between both singly and doubly hydrogen-bonded molecules. </p> </div> </div> </div>

scholarly journals Sum frequency generation spectroscopy in heterogeneous model catalysis: a minireview of CO-related processes

2021 ◽  
Author(s):  
Xia Li ◽  
Günther Rupprechter
Keyword(s):  
Surface Science ◽  
Science Studies ◽  
Ambient Pressure ◽  
Sum Frequency Generation ◽  
Heterogeneous Model ◽  
Model Catalysis ◽  
Sum Frequency ◽  
Pressure Surface ◽  
Sum Frequency Generation Spectroscopy ◽  
Frequency Generation

Sum frequency generation (SFG) vibrational spectroscopy is applied to ambient pressure surface science studies of adsorption and catalytic reactions at solid/gas interfaces.

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