Rod Packings and Metal−Organic Frameworks Constructed from Rod-Shaped Secondary Building Units

Rosi, Nathaniel L.; Kim, Jaheon; Eddaoudi, Mohamed; Chen, Banglin; O’Keeffe, Michael; Yaghi, Omar M.

doi:10.1021/ja045123o

Cited by 2,312 publications

(1,703 citation statements)

References 37 publications

Supporting

Mentioning

1,628

Contrasting

Unclassified

Order By: Relevance

“…The center-of-mass translation and molecular rotation of H 2 are found to attribute zero point energy (ZPE) of ∼20 meV and ∼10 meV, respectively, to the total energy of the MOF-H 2 system. As a result the effective binding is about 100 meV, which is close to the experimentally measured value of ∼90 meV [2,3].Furthermore, we find that the adsorbed H 2 is a threedimensional quantum rotor at both the primary and secondary binding sites. The original J = 1 triplet state splits into three nondegenerate levels, which imply three distinct para to ortho excitation energies.…”

supporting

confidence: 86%

“…A very recent paper studied the rotational transition in another MOF (HKUST-1) with generalized gradient approximation (GGA) calculations [9]. However, GGA is known to fail for cases where the binding is dominated by van der Waals interactions, and only a preliminary theoretical picture was obtained.Here using vdW-DF [1], implemented via the efficient algorithm of two of us [10], we calculated the dynamical properties as well as the binding energy of H 2 adsorbed in MOF-74 structure, which has been demonstrated to increase both the H 2 affinity [5] and hydrogen density [2] due to the unsaturated metal sites [3]. The primary binding sites associated with metal atoms are confirmed by our calculations with a binding energy of 130 meV, while the LDA and GGA results are 230 and 46 meV respectively [5].…”

mentioning

confidence: 99%

See 1 more Smart Citation

Energetics and Dynamics ofH2Adsorbed in a Nanoporous Material at Low Temperature

et al. 2009

View full text Add to dashboard Cite

Molecular hydrogen adsorption in a nanoporous metal organic framework structure (MOF-74) was studied via van der Waals density-functional calculations. The primary and secondary binding sites for H2 were confirmed. The low-lying rotational and translational energy levels were calculated, based on the orientation and position dependent potential energy surface at the two binding sites. A consistent picture is obtained between the calculated rotational-translational transitions for different H2 loadings and those measured by inelastic neutron scattering exciting the singlet to triplet (para to ortho) transition in H2. The H2 binding energy after zero point energy correction due to the rotational and translational motions is predicted to be ∼100 meV in good agreement with the experimental value of ∼90 meV.PACS numbers: 68.43. Bc, 68.43.Fg, 84.60.Ve The adsorption of molecules within the nanopores of a sparse material and their low-lying excitations provide rich phenomena of fundamental interest that are seldom explored by first principles methods, even for molecules as simple as H 2 . For example, one can ask how the wellknown para-ortho transition of H 2 survives in a recognizable form in the presence of the rotational barriers and hindrances provided by the adsorbing material, and how it changes for different concentrations of H 2 . The necessity of proper treatment of van der Waals interactions has foiled traditional density functional treatments. Here, by using the van der Waals density functional (vdW-DF) of Dion et al.[1], we are able to predict a picture of the low-lying excitations which provides a credible match for the results of inelastic neutron diffraction (INS) [2] for different hydrogen loadings in a nanoporous material of a type thought to provide a possible path toward future hydrogen storage technology.The material studied here is a metal-organic framework (MOF) compound, namely the material that has been called , chosen because of recent inelastic neutron scattering measurements [2] with varying amounts of H 2 adsorption. More generally MOFs are a relatively new class of materials which are composed of metal clusters connected by organic ligands [4]. The search for a MOF structure with high binding strength to H 2 has become very active recently [5,6]. The dynamical properties of the adsorbed dihydrogen such as vibrational and hindered rotational motion play a significant role in determining the H 2 binding energy, especially for caged structures with nanopores. This area is even less explored than the modeling of hydrogen uptake based only on the depth of the potential well. An attempt along this line studied the rotational transition of H 2 adsorbed over benzene molecule which is often a fraction of the organic linker in MOF materials [7]. However, the interaction between full MOF and H 2 usually differs significantly from that between a fraction of MOF and H 2 [8]. A very recent paper studied the rotational transition in another MOF (HKUST-1) with generalized gradient approximation (GGA) ca...

show abstract

supporting

confidence: 86%

mentioning

confidence: 99%

Energetics and Dynamics ofH2Adsorbed in a Nanoporous Material at Low Temperature

et al. 2009

View full text Add to dashboard Cite

show abstract

“…M‐MOF‐74, also known as M‐CPO‐27 or M 2 (dobdc) (M=transition‐metal ion; dobdc=2,5‐dioxido‐1,4‐benzene dicarboxylate) also has coordinatively unsaturated metal sites 73, 74. Fe‐MOF‐74 has a honeycomb structure with open metal sites towards large pores of about 15 Å in diameter (Figure 16).…”

Section: Separating C4 Hydrocarbons With Mofsmentioning

confidence: 99%

Sustainable Separations of C₄‐Hydrocarbons by Using Microporous Materials

et al. 2017

View full text Add to dashboard Cite

Petrochemical refineries must separate hydrocarbon mixtures on a large scale for the production of fuels and chemicals. Typically, these hydrocarbons are separated by distillation, which is extremely energy intensive. This high energy cost can be mitigated by developing materials that can enable efficient adsorptive separation. In this critical review, the principles of adsorptive separation are outlined, and then the case for C4 separations by using zeolites and metal–organic frameworks (MOFs) is examined. By analyzing both experimental and theoretical studies, the challenges and opportunities in C4 separation are outlined, with a focus on the separation mechanisms and structure–selectivity correlations. Zeolites are commonly used as adsorbents and, in some cases, can separate C4 mixtures well. The pore sizes of eight‐membered‐ring zeolites, for example, are in the order of the kinetic diameters of C4 isomers. Although zeolites have the advantage of a rigid and highly stable structure, this is often difficult to functionalize. MOFs are attractive candidates for hydrocarbon separation because their pores can be tailored to optimize the adsorbate–adsorbent interactions. MOF‐5 and ZIF‐7 show promising results in separating all C4 isomers, but breakthrough experiments under industrial conditions are needed to confirm these results. Moreover, the flexibility of the MOF structures could hamper their application under industrial conditions. Adsorptive separation is a promising viable alternative and it is likely to play an increasingly important role in tomorrow's refineries.

show abstract

“…Vibrational frequencies are computed at the Γ point on optimized structure (forces <10 meV/Å) from a dynamical matrix obtained through a finite difference approach. 33 and its promise for CO 2 capture has been widely recognized. 34−38 The structure is based on coordinated carboxyl and hydroxy groups (dobdc 4 Ca-BTT is a sodalite-type MOF of the form Na 3 [(Ca 4 Cl) 3 (BTT) 8 ] 2 , similar to those recently synthesized by Long and co-workers.…”

Section: ■ Computational Detailsmentioning

confidence: 99%

CO₂ Capture by Metal–Organic Frameworks with van der Waals Density Functionals

2012

View full text Add to dashboard Cite

We use density functional theory calculations with van der Waals corrections to study the role of dispersive interactions on the structure and binding of CO 2 within two distinct metal−organic frameworks (MOFs): Mg-MOF74 and Ca-BTT. For both classes of MOFs, we report calculations with standard gradient-corrected (PBE) and five van der Waals density functionals (vdW-DFs), also comparing with semiempirical pairwise corrections. The vdW-DFs explored here yield a large spread in CO 2 −MOF binding energies, about 50% (around 20 kJ/ mol), depending on the choice of exchange functional, which is significantly larger than our computed zero-point energies and thermal contributions (around 5 kJ/mol). However, two specific vdW-DFs result in excellent agreement with experiments within a few kilojoules per mole, at a reduced computational cost compared to quantum chemistry or many-body approaches. For Mg-MOF74, PBE underestimates adsorption enthalpies by about 50%, but enthalpies computed with vdW-DF, PBE+D2, and vdW-DF2 (40.5, 38.5, and 37.4 kJ/mol, respectively) compare extremely well with the experimental value of 40 kJ/mol. vdW-DF and vdW-DF2 CO 2 −MOF bond lengths are in the best agreement with experiments, while vdW-C09 x results in the best agreement with lattice parameters. On the basis of the similar behavior of the reduced density gradients around CO 2 for the two MOFs studied, comparable results can be expected for CO 2 adsorption in BTT-type MOFs. Our work demonstrates for this broad class of molecular adsorbate-periodic MOF systems that parameter-free and computationally efficient vdW-DF and vdW-DF2 approaches can predict adsorption enthalpies with chemical accuracy. ■ INTRODUCTIONMetal−organic frameworks (MOFs) are a broad class of threedimensional nanoporous materials that have attracted much attention during the past decade for CO 2 capture from flue gas. 1−6 MOFs consist of metal centers joined by organic molecular "linkers"; there are many possibilities for cation/ linker combinations, and thousands of different MOFs have already been synthesized. 3,5 Understanding mechanisms for CO 2 binding within these frameworks is a fundamental step toward the design of new materials for carbon capture.In order to explore and predict new materials that efficiently capture CO 2 , an accurate quantitative description of both its adsorption energy and geometry is needed. Whereas quantum chemistry methods, such as HF/MP2 or CCSD(T), scale unfavorably with the number of basis functions (N 5 and N 7 ) and are primarily restricted to cluster calculations, density functional theory (DFT) is a very promising framework for studying the mechanism of interaction between CO 2 and extended MOFs. Although DFT is a many-particle framework that includes, in principle, fully nonlocal interactions, its common approximations, such as the local density approximation (LDA) and the generalized gradient approximation (GGA), neglect attractive long-range contributions to van der Waals interactions, so-called London dispersion intera...

show abstract

Rod Packings and Metal−Organic Frameworks Constructed from Rod-Shaped Secondary Building Units

Cited by 2,312 publications

References 37 publications

Energetics and Dynamics ofH2Adsorbed in a Nanoporous Material at Low Temperature

Energetics and Dynamics ofH2Adsorbed in a Nanoporous Material at Low Temperature

Sustainable Separations of C₄‐Hydrocarbons by Using Microporous Materials

CO₂ Capture by Metal–Organic Frameworks with van der Waals Density Functionals

Contact Info

Product

Resources

About

Rod Packings and Metal−Organic Frameworks Constructed from Rod-Shaped Secondary Building Units

Cited by 2,312 publications

References 37 publications

Energetics and Dynamics ofH2Adsorbed in a Nanoporous Material at Low Temperature

Energetics and Dynamics ofH2Adsorbed in a Nanoporous Material at Low Temperature

Sustainable Separations of C4‐Hydrocarbons by Using Microporous Materials

CO2 Capture by Metal–Organic Frameworks with van der Waals Density Functionals

Contact Info

Product

Resources

About

Sustainable Separations of C₄‐Hydrocarbons by Using Microporous Materials

CO₂ Capture by Metal–Organic Frameworks with van der Waals Density Functionals