Theoretical Investigations on the Chemical Bonding, Electronic Structure, And Optical Properties of the Metal−Organic Framework MOF-5

Abstract

The chemical bonding, electronic structure, and optical properties of metal-organic framework-5 (MOF-5) were systematically investigated using ab initio density functional calculations. The unit cell volume and atomic positions were optimized with the Perdew-Burke-Ernzerhof (PBE) functional leading to a good agreement between the experimental and the theoretical equilibrium structural parameters. The calculated bulk modulus indicates that MOF-5 is a soft material. The estimated band gap from a density of state (DOS) calculation for MOF-5 is about 3.4 eV, indicating a nonmetallic character. As MOFs are considered as potential materials for photocatalysts, active components in hybrid solar cells, and electroluminescence cells, the optical properties of this material were investigated. The detailed analysis of chemical bonding in MOF-5 reveals the nature of the Zn-O, O-C, H-C, and C-C bonds, that is, Zn-O having mainly ionic interaction whereas O-C, H-C, and C-C exhibit mainly covalent interactions. The findings in this paper may contribute to a comprehensive understanding about this kind of material and shed insight into the synthesis and application of novel and stable MOFs.

Ten new predicted covalent organic frameworks with strong optical response in the visible and near infrared

“…These results may guide future synthetic efforts on these materials. A series of previous studies [42][43][44][45][46][47][48] have firmly established the viability of our approach in evaluating the energetic stability of experimentally synthesized materials (e.g., IRMOF-1, 42,43 IRMOF-10, 44 IRMOF-14, 45 IRMOF-993, 46 and Zn 4 O(FMA) 3 47 ). The estimated large negative values of formation energy support the experimental results of synthesizing these MOF materials.…”

“…The methodology used for the calculation of optical properties has been proven to be reasonable and compared favorably with corresponding experimental spectra in a series of previous papers from our group. [42][43][44][45][46][47][48][49][50]79,80 To evaluate the stability of the predicted novel COFs, we performed ab initio Born-Oppenheimer molecular dynamics (BOMD) simulations' two representative examples C 4 C and Si 4 C. The scalar-relativistic DFT and Tkatchenko-Scheffler (TS) methods were used in CASTEP 35 in Materials Studio 7.0. MD simulation in NVT ensemble was carried out for 10 ps with a time step of 1.0 fs (parameters: accuracy fine, SCF = 3 × 10 −6 , smearing = 0.04, DIIS = 20, Nosé-Hoover, 51 Nosé Q = 2, Nosé chain length = 2).…”

“…One can compare to the 3-20 GPa for 3D COFs estimated by Lukose et al 28 Also, the Voigt bulk moduli are 21.6 and 4.9 GPa for 3D COF-102 and -108, respectively, predicted by Zhou et al 54 The calculated bulk modulus materials are up to 50% larger than those of prototypical IRMOF-1 (∼15.4 GPa.). 42 This conversion to COF structures is a general way to systematically arrive at more mechanically stable porous materials.…”

Metal-ligand bond lengths and strengths: are they correlated? A detailed CSD analysis

“…. significant differences may arise from the isolated nature of the oxide nodes ..." compared to "the organic linker" [15]. In this study we have investigated bond lengths of metal-alkoxides, metal-alcohol, metal-carboxylates, metal-carboxylic acid, metal-imidazolates, metal-imidazole, metaltriazoles and metal-pyridine coordination compounds from the Cambridge Structural Database (CSD) [4], with the aim to find out whether there are any significant structural indications to classify these compounds into two distinct species.…”

The effect of cluster size on the optical band gap energy of Zn-based metal–organic frameworks

“…This well isolated structural arrangement results in molecular-like electronic structures and leads to bands with minimal dispersion. [16][17][18][19][20][21][22][23][24] As MOFs are composed of metal or metal oxygen nodes and organic linkers, the electronic structure of a MOF can be influenced by interactions between metal or metal oxygen nodes and ligands. This offers the possibility of chemically tuning the electronic properties of the MOF by exchanging the linkers and/or metal or metal oxygen nodes.…”