Electron Density and Dielectric Properties of Highly Porous MOFs: Binding and Mobility of Guest Molecules in Cu₃(BTC)₂ and Zn₃(BTC)₂

Abstract

Two isostructural highly porous metal−organic frameworks, the wellknown {Cu 3 (BTC) 2 } n (BTC = 1,3,5-benzenetricarboxylate), often appointed with the name HKUST-1, and {Zn 3 (BTC) 2 } n , have been investigated as models for the buildup of dielectric properties, differentiating the role of chemi-and physisorbed guest molecules and that of specific intraframework and framework-guest linkages. For this purpose, electron charge density analysis, impedance spectroscopy, density functional theory simulations, and atomic partitioning of the polarizabilities have been exploited. These analyses at different degrees of pores filling enabled one to observe structural and electronic changes induced by guest molecules, especially when chemisorbed. The electrostatic potential inside the pores allows one to describe the absorption mechanism and to estimate the polarization of guests induced by the framework. The dielectric constant shows very diverse frequency dependence and magnitude of real and imaginary components as a consequence of (I) capture of guest molecules in the pores during synthesis, (II) MOF activation, and (III) water absorption from the atmosphere after activation. Comparison with calculated static-dielectric constant and atomic polarizabilities of the material has allowed for evaluating building blocks' contribution to the overall property, paving the way for reverse crystal engineering of these species.

Formate-mediated magnetic superexchange in the model hybrid perovskite [(CH3)2NH2]Cu(HCOO)3

“…On the contrary, the eq-ax formate ligand has an absolute charge that is only slightly reduced from the formal À1 ionic value, suggesting that the axial Cu-O interactions have a predominately ionic character, in keeping with previous studies. 35,36 These empirical differences in Cu-O covalency, and their relationship to the different J eq-eq and J eq-ax exchange interactions, can be understood in terms of the electronic orbital configuration of the formate and Cu ions, discussed in detail in the following.…”

Integration of High‐Performance Cost‐Effective Copper‐Metal‐Organic‐Nanocluster‐based Gate Dielectric for Next‐Generation CMOS Applications

“…The dielectric properties of MOCs are strongly governed by the type, size, composition, functionalization of organic linker molecules as well as inorganic metal nodes which can be utilized to engineer its bandgap and dielectric constant. [ 30,31 ] The Cu 2+ metal node with open‐shell metal ion [ 29 ] , large radius, less electrical conductivity, high activation energy, charge density [ 31 ] , and single valency as compared with counterpart metal nodes provide large bandgap and excellent insulating properties to the Cu‐MOCs. [ 5,46,47 ] Small conjugated chains with a single COOH group attached to the benzene ring in m‐Toulic acid (MTA) organic linker [ 48 ] along with the presence of acetonitrile in small quantities as a guest solvent molecule aid in achieving the desired large bandgap and high dielectric constant in the Cu‐MOCs.…”

“…Not only that, but the novel materials like MOFs correspondingly possess highly tunable physical, electronic, and mechanical properties, which make them exemplary gate dielectric candidates for future CMOS integrated circuits applications. Beforehand, metal‐organic‐clusters (MOCs) have been widely explored as active materials such as conductors [ 25,26 ] , semiconductors [ 2,27 ] , and insulating [ 28–34 ] , gate dielectrics in various electronic applications such as MOS‐Cs [ 20 ] , OFETs [ 8 ] , etc. [ 3,35–38 ] Anqi Hu et al.…”

“…[ 42 ] However, with entrapping or coordination of polar guest particles which are typically free to move accompany high polarizability into the nanoporous materials, illustrating the opportunity to tune host‐guest interactions and certainly a large dielectric constant, higher thermal and mechanical stability could be achieved. [ 29,42 ] It might be possible that the obtained reliable thin films of MOCs exhibit the dielectric constant that is more than three times higher than that of the bulk MOC material. [ 20 ] Owing to these properties, MOCs may be strong potential candidate alternate for high‐κ gate dielectrics in nanoscale CMOS logic devices.…”

Electronic structure of Schiff-base peroxo{2,2′-[1,2-phenylenebis(nitrilomethanylylidene)]bis(6-methoxyphenolato)}titanium(IV) monohydrate: a possible model structure of the reaction center for the theoretical study of hemoglobin

“…On the other hand, using the Hansen-Coppens multipole formalism (Hansen & Coppens, 1978) for accurate diffraction data with satisfactory resolution, providing all necessary corrections, it is possible to obtain a valence electron distribution that reflects bonding properties and interactions in the studied molecule. Despite the low suitability factor (Coppens, 1997), recently published papers of experimental electronic structures of 3d-coordination compounds show reasonable results (Schmøkel et al, 2013;Herich et al, 2018a,b;Fukin et al, 2019;Gao et al, 2019;Scatena et al, 2019).…”