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a) FT-IR spectrum and b) XPS N 1s spectrum of 2DP BTA+PDA . c) Nitrogen adsorption (red ball) and desorption (blue ball) isotherm profiles of 2DP BTA+PDA at 77 K. STP = standard temperature and pressure. d) Pore size distribution of 2DP BTA+PDA .
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Metal‐Organic Frameworks (MOFs) nanofilms offer new perspectives as active layers in memristor devices owing to their large surface area, high chemical and thermal stability, permanent porosity and tunable structure. Though various methods have been reported for the preparation of MOF nanofilms, development of new methods to improve the quality is...
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... 2DP BTA+PDA is transferred to a Si/SiO 2 substrate for morphology characterization through optical microscopy and atomic force microscopy (AFM), as shown in Figure 1b,c and Figure S1 in the Supporting Information. The as-grown 2DP BTA+PDA films show good uniformity and evenly dispersed C, N, and O ( Figure S2, Supporting Information), giving further evidence of the homogeneity of the films. In addition, the ultrathin 2DP BTA+PDA film with a thickness of 1.8 ± 0.2 nm shows good freestanding ability, which can be observed on a bare copper mesh by scanning electron microscopy (SEM, Figure 1d). ...
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... gain insight into the chemical structure, the 2DP BTA+PDA film has been characterized using attenuated total reflectance FTIR (ATR FTIR, Figure 2a) and X-ray photoelectron spectroscopy (XPS). Features originating from the imine bonds (CN) (1621 cm −1 ) in 2DP BTA+PDA in the IR spectrum confirm the occurrence of the Schiff base reaction. ...
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... addition, the accompanied stretching bands at 1694 and 3200-3400 cm −1 indicate the presence of unreacted aldehyde and amino groups of the BTA and PDA precursors, respectively. In the X-ray photoelectron spectrum shown in Figure 2b, the N 1s signal of 2DP BTA+PDA can be fitted with two peaks with binding energies at 398.7 and 399.9 eV, which are attributed to the imine bond and to the unreacted -NH 2 of PDA, respectively. Both the FTIR and XPS results indicate that the reactive groups of the two precursors did not fully participate in the Schiff base reaction, which leads to the amorphous nature of the film as observed by HRTEM. ...
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... N 2 adsorption results at 77 K (Figure 2c) of the 2DP BTA+PDA film show an irreversible sorption profile with typical type I sorption characteristics. The Brunauer-Emmett-Teller (BET) surface area is 74.4 m 2 g −1 , and the pore volume is 8.82 × 10 −2 cm 3 g −1 . ...
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... Brunauer-Emmett-Teller (BET) surface area is 74.4 m 2 g −1 , and the pore volume is 8.82 × 10 −2 cm 3 g −1 . The pore size distribution calculated with nonlocal density functional theory (NLDFT) shows a sharp peak at 1.41 nm (Figure 2d), which represents the intrinsic pores of 2DP BTA+PDA , while the microscopic pores ranging between 20 and 150 nm are attributed to defect-induced larger pores. ...
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... The air/liquid interfacial synthetic technique allows us to create free-standing, orientationally controlled ultrathin MOF nanosheets. Although many reports suggest that the electronic functions of MOF nanosheets largely correlate with their structure, size, morphology, and chemical composition, 35,44,45,54,63 a detailed understanding of the variation in electronic properties by such changes is still unexplored because available fabrication methodologies for obtaining MOF nanosheets with targeted characteristics have not been established yet. Our results show that the spread solution concentration is an important factor for the formation of triphenylene-based MOF nanosheets with rich π electrons and can provide fundamental knowledge to develop the necessary methods for fabrication of well-controlled conductive MOF nanosheets. ...
Metal-organic frameworks (MOFs)─crystalline coordination polymers─with unique characteristics such as structural designability accompanied by tunable electronic properties and intrinsic uniform nanopores have become the platform for applications in diverse scientific areas ranging from nanotechnology to energy/environmental sciences. To utilize the superior features of MOF in potential applications, the fabrication and integration of thin films are of importance and have been actively sought. Especially, downsized MOFs into nanosheets can act as ultimately thin functional components in nanodevices and potentially display unique chemical/physical properties rarely seen in bulk MOFs. Assembling nanosheets by aligning amphiphilic molecules at the air/liquid interface has been known as the Langmuir technique. By utilizing the air/liquid interface as a reaction field between metal ions and organic ligands, MOFs are readily formed into the nanosheet state. The expected features in MOF nanosheets including electrical conduction largely depend on the nanosheet characteristics such as lateral size, thickness, morphology, crystallinity, and orientation. However, their control has not been achieved as yet. Here, we demonstrate how changing the concentration of a ligand spread solution can modify the assembly of MOF nanosheets, composed of 2,3,6,7,10,11-hexaiminotriphenylene (HITP) and Ni2+ ions (HITP-Ni-NS), at the air/liquid interface. A systematic increase in the concentration of the ligand spread solution leads to the enlargement of both the lateral size and the thickness of the nanosheets while retaining their perfect alignment and preferred orientation. On the other hand, at much higher concentrations, we find that unreacted ligand molecules are included in HITP-Ni-NS, introducing disorder in HITP-Ni-NS. These findings can develop further sophisticated control of MOF nanosheet features, accelerating fundamental and applied studies on MOFs.
... 42 Furthermore, the conductivity of single domains surpasses the values of polycrystals. 10 Although surface modification of the substrate used, 36,43 introduction of polymers into the subphase 39 and surface compression can be employed in order to improve coverage and continuity of HITP-Ni-NS, their full control is unestablished. 39 Furthermore, no methodology has been proposed in order to enlarge the crystal size of HITP-Ni-NS in the air/liquid interfacial synthesis. ...
... 10 Although surface modification of the substrate used, 36,43 introduction of polymers into the subphase 39 and surface compression can be employed in order to improve coverage and continuity of HITP-Ni-NS, their full control is unestablished. 39 Furthermore, no methodology has been proposed in order to enlarge the crystal size of HITP-Ni-NS in the air/liquid interfacial synthesis. Since the assembly of HITP-Ni-NS largely depends on the coordination bonds and ππ interactions, the fabrication conditions critically influencing such bonds/interactions in HITP-Ni-NS need to be understood. ...
Nanosheets of metal–organic frameworks (MOFs)—porous crystalline materials consisting of metal ions and organic ligands—are actively studied for their intrinsic chemical/physical properties attributed to the reduced dimensionality and for their potential to function as ideal components of nanodevices, especially when electrical conduction is present. Air/liquid interfacial synthesis is a promising technique to obtain highly oriented MOF nanosheets. However, rational control of size and shape combined with the aimed functionality remains an important issue to address making it necessary to research the critical factors governing nanosheet characteristics in the interfacial synthesis. Here, we investigate the influence of the solvent—methanol (MeOH) versus N,N-dimethylformamide (DMF)—used to prepare a ligand spread solution on an assembly of MOF nanosheets composed of Ni2+ and 2,3,6,7,10,11-hexaiminotriphenylene (HITP) (HITP-Ni-NS). We find that the macroscopic morphological uniformity in the micrometer scale is higher when DMF is used as the solvent. Regarding the microscopic crystalline domain, molecules of DMF with relatively high polarity and boiling point are involved in HITP-Ni-NS formation, hindering its growth and resulting in nanosheets with slightly smaller lateral size than that grown when MeOH is used. These findings provide crucial guidelines towards establishing a judicious strategy for creating desired MOF nanosheets at the air/liquid interface, thereby driving forward research on both fundamental and applied aspects of this field.
... Alizadeh et al. reported two techniques for simultaneous growth of MOFs films on two electrodes at one time [79]. One is similar to the above example. ...
Facing the explosive growth of data, a number of new micro-nano devices with simple structure, low power consumption, and size scalability have emerged in recent years, such as neuromorphic computing based on memristor. The selection of resistive switching layer materials is extremely important for fabricating of high performance memristors. As an organic-inorganic hybrid material, metal-organic frameworks (MOFs) have the advantages of both inorganic and organic materials, which makes the memristors using it as a resistive switching layer show the characteristics of fast erasing speed, outstanding cycling stability, conspicuous mechanical flexibility, good biocompatibility, etc. Herein, the recent advances of MOFs-based memristors in materials, devices, and applications are summarized, especially the potential applications of MOFs-based memristors in data storage and neuromorphic computing. There also are discussions and analyses of the challenges of the current research to provide valuable insights for the development of MOFs-based memristors.
... The strong absorption bands of both materials are in the UV region, which suggest that they both have wide band gaps. [37] In addition, the two characteristic absorption bands of Cu 3 (HHTP) 2 are attributed to 368 nm (π-π* transition) and 688 nm (ligand-to-metal charge transfer band). The Cu 3 (HHTP) 2 /ZnO device was also tested as shown in Figure 2c, and the strong absorption band of the device is around 365 nm, indicating its potential for UV detection. ...
... In addition, there are also two distinct satellite peaks at 943.3 eV and 963 eV. [37] The existence of characteristic peaks of Cu 2 + and satellite peaks further supports the successful synthesis of Cu 3 (HHTP) 2 . [34] O 1s can be fitted by the peaks of À CÀ OÀ , À C=OÀ , and À CuÀ OÀ in Figure 2i, and the appearance of these peaks also reflects the binding between Cu 2 + ions and HHTP ligands. ...
Two‐dimensional conductive metal–organic frameworks (2D c‐MOFs) are a family of highly tunable and electrically conducting materials that can be utilized in optoelectronics. A major issue of 2D c‐MOFs for photodetection is their poor charge separation and recombination dynamics upon illumination. This study demonstrates a Cu3(HHTP)2/ZnO type‐II heterojunction ultraviolet (UV) photodetector fabricated by layer‐by‐layer (LbL) deposition, in which the charge separation of photogenerated carriers is enhanced. At optimized MOF layer cycles, the device achieves a responsivity of 78.2 A/W and detectivity of 3.8×10⁹ Jones at 1 V. Particularly, the device can be operated in the self‐powered mode with an ultrafast response time of 70 μs, which is the record value for MOF‐based photodetectors. In addition, even after 1000‐time bending of 180°, the flexible device maintains stable performance. This flexible MOF‐based UV photodetector with anti‐fatigue and anti‐bending properties provides strong implication to wearable optoelectronics.
... Metal-Organic Frameworks (MOFs), also known as porous coordination polymers, are a class of compounds with mesh structures formed by the self-assembly of metal ions or clusters of metals with multi-dentate organic ligands containing oxygen, nitrogen, etc (Jiao et al., 2021;Zhang et al., 2021c;Liu et al., 2021). The metal ions or clusters of MOFs and the variety of organic ligands, and the diversity of linking approaches between metals and ligands, make MOFs having the advantages of traditional inorganic materials, such as ultra-high surface area and porosity, lower density, pore size and structural flexibility. ...
In general, the functional crystalline porous materials (CPM) are composed of an ordered structure with distinct molecular spaces for interrelating secondary molecules. In this context, emerging porous and crystalline materials, especially metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) have attracted much attentions for several applications. Thus existing synthetic methods are randomly applied for the large scale production of COFs/MOFs (CPM) and new synthetic strategies are also developed. Herein, we have summarized the synthetic methods for the synthesis of functional crystalline porous materials with recent examples, following the advantages and disadvantages of each method. The possible applications of these materials are also discussed to express the practical viability of these materials and finally future perspectives are provided.
... Multilevel memory behavior can currently be achieved either by adjusting internal materials (multiple memory mechanisms; depth/intensity of electronic defects; types of electronic defects or different charge trapping sites; molecular end functional groups (stacking methods)) or external conditions (controlling test parameters (compliance current, set/reset voltage); doping; light; ultraviolet; particle size). [6][7][8][9][10][11][12][13] However, the multilevel memory device based on concept of multiple ion migration channels has not been reported. ...
Nowadays, most manufacturing memory devices are based on materials with electrical bistability (i. e., “0” and “1”) in response to an applied electric field. Memory devices with multilevel states are highly desired so as to produce high‐density and efficient memory devices. Herein, we report the first multichannel strategy to realize a ternary‐state memristor. We make use of the intrinsic sub‐nanometer channel of pillar[5]arene and nanometer channel of a two‐dimensional imine polymer to construct an active layer with multilevel channels for ternary memory devices. Low threshold voltage, long retention time, clearly distinguishable resistance states, high ON/OFF ratio (OFF/ON1/ON2=1 : 10 : 10³), and high ternary yield (75 %) were obtained. In addition, the flexible memory device based on 2DPTPAZ+TAPB can maintain its stable ternary memory performance after being bent 500 times. The device also exhibits excellent thermal stability and can tolerate a temperature as high as 300 °C. It is envisioned that the results of this work will open up possibilities for multistate, flexible resistive memories with good thermal stability and low energy consumption, and broaden the application of pillar[n]arene.
In this study, we demonstrate multilevel operation of nonvolatile resistive random-access memory (ReRAM) devices using thin films of an ionic liquid crystal (ILC), 1-dodecyl-3-methylimidazolium tetrafluoroborate ([C 12 mim][BF 4 ]), as a resistive switching...
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Memristors have recently become powerful competitors toward artificial synapses and neuromorphic computation, arising from their structural and electrical similarity to biological synapses and neurons. From the diversity of materials, numerous organic and inorganic materials have proven to exhibit great potential in the application of memristors. Herein, this work focuses on a class of memristors based on organic frameworks (OFs) materials, and pay attention to the most advanced experimental demonstrations. First, the typical device structures and memristive switching mechanisms are introduced. Second, the latest progress of OFs‐based memristors is comprehensively summarized, including metal‐organic frameworks (MOFs), covalent organic frameworks (COFs), and hydrogen‐bonded organic frameworks (HOFs), as well as their applications in data storage, artificial synapses, and neuromorphic devices. Finally, the future challenges and prospects of OFs‐based memristors are deeply discussed.
