Programmed Molecular Assembly of Abrupt Crystalline Organic/Organic Heterointerfaces Yielding Metal‐Organic Framework Diodes with Large On‐Off Ratios

Chandresh, Abhinav; Liu, Xiaojing; Wöll, Christof; Heinke, Lars

doi:10.1002/advs.202001884

Cited by 25 publications

(20 citation statements)

References 55 publications

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“…For practical applications, the roughness of MOF thin films deposited using the LbL method is a very important parameter, especially for advanced applications of MOFs where, e.g., sharp heterojunctions are required [ 46 ] or very flat surfaces are needed. In order to investigate the effect of deposition temperature, simulations of four deposition cycles were carried out, and the final structures were analyzed for eight different temperatures.…”

Section: Resultsmentioning

confidence: 99%

Modeling the Layer-by-Layer Growth of HKUST-1 Metal-Organic Framework Thin Films

et al. 2021

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Metal organic frameworks have emerged as an important new class of materials with many applications, such as sensing, gas separation, drug delivery. In many cases, their performance is limited by structural defects, including vacancies and domain boundaries. In the case of MOF thin films, surface roughness can also have a pronounced influence on MOF-based device properties. Presently, there is little systematic knowledge about optimal growth conditions with regard to optimal morphologies for specific applications. In this work, we simulate the layer-by-layer (LbL) growth of the HKUST-1 MOF as a function of temperature and reactant concentration using a coarse-grained model that permits detailed insights into the growth mechanism. This model helps to understand the morphological features of HKUST-1 grown under different conditions and can be used to predict and optimize the temperature for the purpose of controlling the crystal quality and yield. It was found that reactant concentration affects the mass deposition rate, while its effect on the crystallinity of the generated HKUST-1 film is less pronounced. In addition, the effect of temperature on the surface roughness of the film can be divided into three regimes. Temperatures in the range from 10 to 129 °C allow better control of surface roughness and film thickness, while film growth in the range of 129 to 182 °C is characterized by a lower mass deposition rate per cycle and rougher surfaces. Finally, for T larger than 182 °C, the film grows slower, but in a smooth fashion. Furthermore, the potential effect of temperature on the crystallinity of LbL-grown HKUST-1 was quantified. To obtain high crystallinity, the operating temperature should preferably not exceed 57 °C, with an optimum around 28 °C, which agrees with experimental observations.

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Section: Resultsmentioning

confidence: 99%

Modeling the Layer-by-Layer Growth of HKUST-1 Metal-Organic Framework Thin Films

et al. 2021

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“…The presence of tuneable, built‐in electric fields opens up the possibility of engineering band structures and aligning electronic levels, in particular in connection with the loading of charge‐donating guests (e.g., C 60 [ 51 ] ) into the pores of the SURMOFs. [ 52 ] In principle, the magnitude of the electrostatic potential shifts can be increased further—potentially even to the point where charge transfer from the substrate to the lowest unoccupied states at the outer SURMOF surface takes place. A further, highly promising route for future research is to orient asymmetric guests by embedding them into the pores of the NC SURMOFs, in which cases charge transfer might lead to further enhancement of the NLO properties.…”

Section: Discussionmentioning

confidence: 99%

Avoiding the Center‐Symmetry Trap: Programmed Assembly of Dipolar Precursors into Porous, Crystalline Molecular Thin Films

et al. 2021

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Liquid‐phase, quasi‐epitaxial growth is used to stack asymmetric, dipolar organic compounds on inorganic substrates, permitting porous, crystalline molecular materials that lack inversion symmetry. This allows material fabrication with built‐in electric fields. A new programmed assembly strategy based on metal–organic frameworks (MOFs) is described that facilitates crystalline, noncentrosymmetric space groups for achiral compounds. Electric fields are integrated into crystalline, porous thin films with an orientation normal to the substrate. Changes in electrostatic potential are detected via core‐level shifts of marker atoms on the MOF thin films and agree with theoretical results. The integration of built‐in electric fields into organic, crystalline, and porous materials creates possibilities for band structure engineering to control the alignment of electronic levels in organic molecules. Built‐in electric fields may also be used to tune the transfer of charges from donors loaded via programmed assembly into MOF pores. Applications include organic electronics, photonics, and nonlinear optics, since the absence of inversion symmetry results in a clear second‐harmonic generation signal.

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“…Therefore, the significant aspects of this strategy are that it can promote the conformal and directional overgrowth of MOFs on the surface of other MOFs, which provides more possibilities for the combined growth of two MOFs. [ 147–153 ] The structure formed by the functional substrates and MOFs material often exhibits more stable and superior performance than a single structure.…”

Section: Random Growth Of Mof‐on‐mofmentioning

confidence: 99%

Rational Design and Growth of MOF‐on‐MOF Heterostructures

Chai

Pan

et al. 2021

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Multiporous metal‐organic frameworks (MOFs) have emerged as a subclass of highly crystalline inorganic‐organic materials, which are endowed with high surface areas, tunable pores, and fascinating nanostructures. Heterostructured MOF‐on‐MOF composites are recently becoming a research hotspot in the field of chemistry and materials science, which focus on the assembly of two or more different homogeneous or heterogeneous MOFs with various structures and morphologies. Compared with one single MOF, the dual MOF‐on‐MOF composites exhibit unprecedented tunability, hierarchical nanostructure, synergistic effect, and enhanced performance. Due to the difference of inorganic metals and organic ligands, the lattice parameters in a, b, and c directions in the single crystal cells could bring about subtle or large structural difference. It will result in the composite material with distinct growth methods to obtain secondary MOF grown from the initial MOF. In this review, the authors wish to mainly outline the latest synthetic strategies of heterostructured MOF‐on‐MOFs and their derivatives, including ordered epitaxial growth, random epitaxial growth, etc., which show the tutorial guidelines for the further development of various MOF‐on‐MOFs.

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Programmed Molecular Assembly of Abrupt Crystalline Organic/Organic Heterointerfaces Yielding Metal‐Organic Framework Diodes with Large On‐Off Ratios

Cited by 25 publications

References 55 publications

Modeling the Layer-by-Layer Growth of HKUST-1 Metal-Organic Framework Thin Films

Modeling the Layer-by-Layer Growth of HKUST-1 Metal-Organic Framework Thin Films

Avoiding the Center‐Symmetry Trap: Programmed Assembly of Dipolar Precursors into Porous, Crystalline Molecular Thin Films

Rational Design and Growth of MOF‐on‐MOF Heterostructures

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