Contribution of Density Functional Theory to Microporous Materials for Carbon Capture

Cockayne, Eric

doi:10.1002/9781119231059.ch8

Cited by 2 publications

(2 citation statements)

References 90 publications

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“…In a previous work, 23 we used experimental measurements and density-functional-theory (DFT) calculations 24 to investigate in detail the structural changes in Ni-Bpene upon CO 2 adsorption. We concluded that rotations of the Bpene ligands occur as the structure goes from low CO 2 filling to maximum CO 2 uptake, along with a substantial expansion of the unit cell.…”

Section: ■ Introductionmentioning

confidence: 99%

Density Functional Theory Study of the Structure of the Pillared Hofmann Compound Ni(3-Methyl-4,4′-bipyridine)[Ni(CN)₄] (Ni-BpyMe or PICNIC-21)

et al. 2021

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We use dispersion-corrected density functional theory (DFT) to investigate the structure of the pillared Hofmann compound Ni(3-methyl-4,4′-bipyridine)[Ni(CN)4] (Ni-BpyMe for short, or PICNIC-21). We model the disorder found in experimental X-ray structure refinement via an ensemble of supercells with ordered ligand orientation configurations. The ensemble-averaged structure agrees very well with experiment, except for the positions of the methyl group hydrogen atoms. While the dihedral angles between the bipyridal rings of each BpyMe ligand of the averaged structure is 90°, the local dihedral angles are about 80°. DFT screening of configurations where the crystallographic a/b ratio is constrained to equal 1 fail to find the configurations that are most stable when a/b is set to its distorted experimental value of a/b = 0.86, demonstrating the difficulty of solving pillared Hofmann structures purely theoretically without experimental input. The waviness of the Ni(CN)2 sheets is explained as a tendency to maximize dispersion interactions between these sheets and the methylpyridine rings. This waviness leads to greater residual pore space and greater adsorbate uptake at low pressure compared with the analogous pillared compound Ni-Bpene (PICNIC-60).

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Section: ■ Introductionmentioning

confidence: 99%

Density Functional Theory Study of the Structure of the Pillared Hofmann Compound Ni(3-Methyl-4,4′-bipyridine)[Ni(CN)₄] (Ni-BpyMe or PICNIC-21)

et al. 2021

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“…Density functional theory calculations were performed to complement the experimental measurements and to model the energetics and structural changes upon CO 2 sorption in NiBpene. Although all current density functionals use some approximation to the unknown exact exchange-correlation functional, in practice, DFT that combines the Perdew–Burke–Ernzerhof (PBE) or solid-state PBE (PBEsol) generalized gradient approximation [57,58] with “Hubbard U” corrections for transition metal ions [59] and empirical van der Waals forces has been found to provide a good combination of speed and accuracy for the study of CO 2 sorption in MOFs [60]. Flexible MOFs can have one or more elastic parameters that are extremely small [61].…”

Section: Methodsmentioning

confidence: 99%

Structural Basis of CO2 Adsorption in a Flexible Metal-Organic Framework Material

et al. 2019

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This paper reports on the structural basis of CO2 adsorption in a representative model of flexible metal-organic framework (MOF) material, Ni(1,2-bis(4-pyridyl)ethylene)[Ni(CN)4] (NiBpene or PICNIC-60). NiBpene exhibits a CO2 sorption isotherm with characteristic hysteresis and features on the desorption branch that can be associated with discrete structural changes. Various gas adsorption effects on the structure are demonstrated for CO2 with respect to N2, CH4 and H2 under static and flowing gas pressure conditions. For this complex material, a combination of crystal structure determination and density functional theory (DFT) is needed to make any real progress in explaining the observed structural transitions during adsorption/desorption. Possible enhancements of CO2 gas adsorption under supercritical pressure conditions are considered, together with the implications for future exploitation. In situ operando small-angle neutron and X-ray scattering, neutron diffraction and X-ray diffraction under relevant gas pressure and flow conditions are discussed with respect to previous studies, including ex situ, a priori single-crystal X-ray diffraction structure determination. The results show how this flexible MOF material responds structurally during CO2 adsorption; single or dual gas flow results for structural change remain similar to the static (Sieverts) adsorption case, and supercritical CO2 adsorption results in enhanced gas uptake. Insights are drawn for this representative flexible MOF with implications for future flexible MOF sorbent design.

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Contribution of Density Functional Theory to Microporous Materials for Carbon Capture

Cited by 2 publications

References 90 publications

Density Functional Theory Study of the Structure of the Pillared Hofmann Compound Ni(3-Methyl-4,4′-bipyridine)[Ni(CN)₄] (Ni-BpyMe or PICNIC-21)

Density Functional Theory Study of the Structure of the Pillared Hofmann Compound Ni(3-Methyl-4,4′-bipyridine)[Ni(CN)₄] (Ni-BpyMe or PICNIC-21)

Structural Basis of CO2 Adsorption in a Flexible Metal-Organic Framework Material

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Contribution of Density Functional Theory to Microporous Materials for Carbon Capture

Cited by 2 publications

References 90 publications

Density Functional Theory Study of the Structure of the Pillared Hofmann Compound Ni(3-Methyl-4,4′-bipyridine)[Ni(CN)4] (Ni-BpyMe or PICNIC-21)

Density Functional Theory Study of the Structure of the Pillared Hofmann Compound Ni(3-Methyl-4,4′-bipyridine)[Ni(CN)4] (Ni-BpyMe or PICNIC-21)

Structural Basis of CO2 Adsorption in a Flexible Metal-Organic Framework Material

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Density Functional Theory Study of the Structure of the Pillared Hofmann Compound Ni(3-Methyl-4,4′-bipyridine)[Ni(CN)₄] (Ni-BpyMe or PICNIC-21)

Density Functional Theory Study of the Structure of the Pillared Hofmann Compound Ni(3-Methyl-4,4′-bipyridine)[Ni(CN)₄] (Ni-BpyMe or PICNIC-21)