Semiconductive Metal-Organic Framework Research Articles

Multi‐Scale Design of Metal–Organic Framework Metamaterials for Broad‐Band Microwave Absorption

AbstractThe development of nanocomposite microwave absorbers is a critical strategy for tackling electromagnetic pollution. However, challenges persist regarding material stability and achieving broadband absorption. Herein, a novel multi−scale design approach for metamaterial absorbers is proposed. First, a series of bimetallic (cobalt and copper) semiconductive metal–organic framework (SC−MOF) crystals with atomically resolved structures are successfully prepared to serve as building blocks for metamaterials. By simply adjusting the concentration ratio of the two ions, the controllable preparation of crystal morphology can be achieved. This enables to precisely tune the absorption peak and bandwidth range of the SC−MOF, resulting in excellent EMW absorption performance (effective absorption bandwidth: 6.16 GHz, minimum reflection loss: −61 dB). Based on this, printable inks are further constructed by encapsulating the SC−MOF in polydimethylsiloxane and 3D‐printed multi−layered metamaterial absorbers based on woodpile porous architecture. The metamaterial absorber demonstrates a near‐perfect absorption in the microwave spectrum (with a bandwidth of 11.33 GHz), closely matching theoretical simulations. This multi−scale design approach, combining precise MOF materials construction with topological structure design, offers new insights for the development of broadband microwave absorbers.

Tetraphenylene-based semiconductive metal-organic framework crystals for direct X-ray detection and imaging.

MOFs have good potential for X-ray detection, but direct X-ray detection in single crystal form is rarely reported. In this work, we successfully synthesized Pb-TCPE, and the single crystal achieves a low detection limit and high detection sensitivity of 4812.6 μC Gyair-1 cm-2, which exhibits great potential for X-ray detection and imaging.

Metal-Carbodithioate-Based 3D Semiconducting Metal-Organic Framework: Porous Optoelectronic Material for Energy Conversion.

Solar energy conversion requires the working compositions to generate photoinduced charges with high potential and the ability to deliver charges to the catalytic sites and/or external electrode. These two properties are typically at odds with each other and call for new molecular materials with sufficient conjugation to improve charge conductivity but not as much conjugation as to overly compromise the optical band gap. In this work, we developed a semiconducting metal-organic framework (MOF) prepared explicitly through metal-carbodithioate "(-CS2)nM" linkage chemistry, entailing augmented metal-linker electronic communication. The stronger ligand field and higher covalent character of metal-carbodithioate linkages─when combined with spirofluorene-derived organic struts and nickel(II) ion-based nodes─provided a stable, semiconducting 3D-porous MOF, Spiro-CS2Ni. This MOF lacks long-range ordering and is defined by a flexible structure with non-aggregated building units, as suggested by reverse Monte Carlo simulations of the pair distribution function obtained from total scattering experiments. The solvent-removed "closed pore" material recorded a Brunauer-Emmett-Teller area of ∼400 m2/g, where the "open pore" form possesses 90 wt % solvent-accessible porosity. Electrochemical measurements suggest that Spiro-CS2Ni possesses a band gap of 1.57 eV (σ = 10-7 S/cm at -1.3 V bias potential), which can be further improved by manipulating the d-electron configuration through an axial coordination (ligand/substrate), the latter of which indicates usefulness as an electrocatalyst and/or a photoelectrocatalyst (upon substrate binding). Transient-absorption spectroscopy reveals a long-lived photo-generated charge-transfer state (τCR = 6.5 μs) capable of chemical transformation under a biased voltage. Spiro-CS2Ni can endure a compelling range of pH (1-12 for weeks) and hours of electrochemical and photoelectrochemical conditions in the presence of water and organic acids. We believe this work provides crucial design principles for low-density, porous, light-energy-conversion materials.

Plasma-Assisted Defect Engineering on p-n Heterojunction for High-Efficiency Electrochemical Ammonia Synthesis.

A defect-rich 2D p-n heterojunction, Cox Ni3- x (HITP)2 /BNSs-P (HITP: 2,3,6,7,10,11-hexaiminotriphenylene), is constructed using a semiconductive metal-organic framework (MOF) and boron nanosheets (BNSs) by in situ solution plasma modification. The heterojunction is an effective catalyst for the electrocatalytic nitrogen reduction reaction (eNRR) under ambient conditions. Interface engineering and plasma-assisted defects on the p-n Cox Ni3-x (HITP)2 /BNSs-P heterojunction led to the formation of both Co-N3 and B…O dual-active sites. As a result, Cox Ni3-x (HITP)2 /BNSs-P has a high NH3 yield of 128.26 ± 2.27µg h-1 mgcat. -1 and a Faradaic efficiency of 52.92 ± 1.83% in 0.1m HCl solution. The catalytic mechanism for the eNRR is also studied by in situ FTIR spectra and DFT calculations. A Cox Ni3- x (HITP)2 /BNSs-P-based Zn-N2 battery achieved an unprecedented power output with a peak power density of 5.40mW cm-2 and an energy density of 240mA h gzn -1 in 0.1m HCl. This study establishes an efficient strategy for the rational design, using defect and interfacial engineering, of advanced eNRR catalysts for ammonia synthesis under ambient conditions.

Waste-treating-waste: Upcycling discarded polyester into metal–organic framework nanorod for synergistic interfacial solar evaporation and sulfate-based advanced oxidation process

Catalytic conversion of waste plastics into semiconductive metal–organic framework (MOF) kills two birds with one stone, since it not merely offers promising possibility to realize freshwater production and water decontamination through interfacial solar evaporation and photocatalysis, but also advances upcycling of waste plastics. Nevertheless, exploiting synergistic photothermal-photocatalysis materials from recycled plastics remains a challenge. Herein, we report a facile solvothermal method of waste poly(ethylene terephthalate) bottles for the massive production of Co-MOF nanorod and construct a dual-functional Co-MOF/carbon nanotube (CNT) solar evaporator integrated with advanced oxidation process for simultaneous wastewater purification and freshwater production. Firstly, we prove that the evaporator owns high sunlight absorption due to the presence of CNT, super-hydrophilicity, and low heat conductivity, which endow it with fine photothermal conversion capability and reduced vaporization enthalpy. Benefiting from the above advantages, Co-MOF/CNT evaporator displays a high evaporation rate of 2.25 kg m−2 h−1 under 1 kW m−2 illumination, when treating tetracycline (TC)-polluted water, along with good mechanical property, high flexibility, long-term stability, and high scalability. Secondly, based on the results of COMSOL and density functional theory calculation, the localized solar heat from CNT and rich open cobalt sites of Co-MOF nanorod are proved to play a synergistic effect in the activation of peroxymonosulfate to generate various oxidation reactive species. Thereby, the dual-functional evaporator achieves a superb TC degradation activity. Lastly, an outdoor device is designed for freshwater generation and catalytic decomposition of TC. The daily freshwater production amount is 4.5 kg m−2, and the TC degradation efficiency is 93.1%. This study not merely advances the upcycling waste plastics into useful products, but also offers a sustainable platform to wastewater purification via a waste-treating-waste strategy.

A two-dimensional semiconductive Cu-S metal-organic framework for broadband microwave absorption

Electromagnetic radiation and pollution are urgent and crucial problems to be solved. Metal-organic framework (MOF) derivates play an important role in the attenuation of electromagnetic waves efficiently. However, limited by the complex pyrolysis process, the chemical composition and crystal structure of MOF were totally destroyed. Inspired by the electrical window (10−6–10 S·cm−1) of microwave absorption materials (MAMs), semiconductive MOF with precise crystal structure is potential to be an ideal microwave absorbent. This work reports a two-dimensional (2D) semiconductive MOF (Cu-S-MOF) as broadband high-performance MAMs. The effective absorption bandwidth (EAB) of the Cu-S-MOF can reach 6.72 GHz (9.68–16.4 GHz) at a thickness of 1.5 mm, and a minimum reflection loss (RLmin) value of −52.8 dB at 1.69 mm. Due to the absence of the pyrolysis process, a well-defined single-crystal structure of Cu-S-MOF can be obtained. A density functional theory (DFT) calculation was performed to illuminate the microwave absorption mechanism. Resistance loss and interfacial polarization loss between the Cu-S layers mainly contribute to the Cu-S-MOF MAMs. The semiconductive MOF towards MAMs provides a facile and effective strategy to tune microwave absorption performance, which can be applied in the electromagnetic protection field.

Duplex-Specific Nuclease-Enabled Target Recycling on Semiconducting Metal-Organic Framework Heterojunctions for Energy-Transfer-Based Organic Photoelectrochemical Transistor miRNA Biosensing.

Semiconductor metal-organic frameworks (MOFs) and heterojunctions have gained increasing attention in many fields, yet their full potential remains largely unexplored. Advanced optobioelectronics are envisioned to create more opportunities for innovative biomedical applications. This study reports a UiO-66-NH2 (U6N)/CdS quantum dots (QDs)-gated organic photoelectrochemical transistor (OPECT) and its application toward energy-transfer-based sensitive microRNA-166a (miRNA-166a) detection assisted by duplex-specific nuclease (DSN)-enabled target recycling. Specifically, a U6N/CdS QDs photoanode was fabricated and shown to be efficiently gating a poly(3,4-ethylenedioxythiophene) doped with poly(styrene sulfonate) (PEDOT/PSS) channel, while the DSN-enabled release of Au-reporters and hybridization upon the U6N/CdS QDs photoanode could significantly inhibit the photoanode response via an energy transfer process and thus modulate the device response, permitting novel dual-amplified optobioelectronic miRNA-166a detection with a low detection limit of 1.0 fM. This work not only features the DSN-amplified miRNA detection via an OPECT route but also unveils the potential of semiconductor MOF heterojunctions for futuristic optobioelectronics.

Millimeter-scale semiconductive metal-organic framework single crystal for X-ray imaging

One of the bottleneck issues in the design of semiconductive metal-organic frameworks is the growth of high-quality single crystals large enough for device fabrication. Here, we report the synthesis and crystal growth of a millimeter-scale semiconductive metal-organic framework (MOF; UO2(SC6H4COO)2(DMF), SCU-15) and further investigate its electrical properties. The single crystal of SCU-15 shows a charge-carrier mobility-lifetime product (μτ) of 2.18 × 10−3 cm2 V−1 and presents a carrier diffusion length exceeding 70 μm under X-ray excitation, which enables a significantly enhanced photocurrent response and detection sensitivity compared with those of the pelleted polycrystalline sample. As a proof of concept, a planar 2 × 3 pixelated detector is constructed to show its potential application in X-ray imaging. This work discloses an example of a millimeter pixel detector based on semiconductive MOF crystals, heralding the opportunity to develop a new generation of radiation-detection sensors.

A Co(II)-based non-interpenetration semiconductive metal-organic framework for photocatalytic degradation of organic dye contaminant

A new Co(II)-based porous metal-organic framework has been obtained, which exhibit excellent photocatalytic activity for methylene blue degradation. • A 3D metal–organic framework featuring two kind of cages constructed by Co 2 (COO) 4 paddle-wheel clusters and btb tritopic linkers has been synthesized and characterized. • The diffuse reflective spectrum (DRS) indicated that Co(II)-based MOF processing semiconductive behavior. • Co(II)-based MOF shows remarkable photocatalytic degradation of methylene blue under visiable light irradiation. A Co(II)-based porous metal-organic framework, Co 6 (btb) 4 (4,4́-bipy) 3 •44DMA ( 1 ) (btb = benzene-1,3,5-tribenzoate, 4,4́-bipy = 4,4′-bipyridine) which is a 3D neutral framework featuring two kind of cages constructed by Co 2 (COO) 4 paddle-wheel clusters and btb tritopic linkers has been synthesized and characterized. The diffuse reflective spectrum (DRS) indicated that the E g value of 1 is 2.85 eV which confirm it processing semiconductive behavior. The photocatalytic degradation of methylene blue dyes in aqueous solution using 1 as photocatalyst was investigated under UV–vis light and visiable light irradiation. The results show that 1 photocatalyst exhibited the photocatalytic activity for methylene blue degradation.

Bromine Vapor Induced Continuous p- to n-Type Conversion of a Semiconductive Metal-Organic Framework Cu[Cu(pdt)2

Guest-promoted modulation of the electronic states in metal-organic frameworks (MOFs) has brought about a new field of interdisciplinary research, including host-guest chemistry and solid-state physics. Although there are dozens of studies on guest-promoted enhancement of the electrical conductivity properties, including stoichiometry, conductive carriers and structure-property relationships have been scarcely studied in detail. Herein, we studied the effects of continuous and controlled bromine vapor doping on structural, optical, thermoelectric, and semiconducting properties of Cu[Cu(pdt)2] (pdt = 2,3-pyrazinedithiolate) as a function of bromine stoichiometry. We demonstrated that the same material could act as both p- and n-type semiconductors by tuning the stoichiometry of Br doped in Brx@Cu[Cu(pdt)2], and a change in the charge-carrier type from holes in pristine MOF to electrons upon bromine vapor doping was observed. Bromine molecules acted as an oxidant, causing the selective oxidation of [CuII(pdt)2] in the host framework. In addition, a redox hopping pathway between the partially oxidized CuII/CuIII center contributed to the enhancement of the electrical conductivity of the MOF.

Reusable radiochromic semiconductive MOF for dual-mode X-ray detection using color change and electric signal

This work puts forward the idea of dual-mode X-ray detection using color change and electric signal, and provides a MOF (metal–organic framework)-based host–guest strategy to synthesize rewritable radiochromic semiconductive materials, which are promising to avoid the lack of digital processing ability and reusability of commercial radiographic/radiochromic films and the non-portability of commercial electric detectors. The obtained semiconductor with photochromism-active viologen exhibited rapid color change from colorless to blue and photocurrent response upon irradiation of X-ray and was easily bleached after thermal annealing for reuse. As an application example, the inner detail of a printed circuit board was successfully revealed through radiochromic imaging. Meanwhile, a single-crystal detector of the semiconductor achieved a sensitivity of 3216 µCGy–1cm−2, which is higher than those of all reported MOF-based detectors and commercial α-Se detectors.

Boosting the Optoelectronic Performance by Regulating Exciton Behaviors in a Porous Semiconductive Metal–Organic Framework

Exciton behaviors including exciton formation and dissociation dynamics play an essential role in the optoelectronic performance of semiconductive materials but remain unexplored in semiconductive metal-organic frameworks (MOFs). Herein, we reveal that the exciton behaviors in semiconductive MOFs can be regulated by framework-guest interactions, a feature often not achievable in traditional inorganic or organic semiconductors. Incorporation of the electron-deficient molecule within the pores of a terbium-based semiconductive MOF (Tb2L2·4H2O·6DMF, L = TATAB3-, 4,4',4″-s-triazine-1,3,5-triyltri-p-aminobenzoate, DMF = N,N-dimethylformamide) results in efficient energy transfer from the MOF skeleton to molecular acceptors, with a yield of up to 77.4%. This interaction facilitates distinctive exciton type conversion, giving rise to modified conductivity and photoelectric performance. We further fabricated a MOF-based X-ray detection device to demonstrate how the new architecture bolsters the optoelectronic efficiency, which outperforms the properties of parent semiconductive MOFs, with more than 60 times and 40 times enhancement of the photocurrent on-off ratio and detection sensitivity, respectively. With judiciously optimized exciton behaviors, the detection device exhibits a high sensitivity of 51.9 μC Gyair-1 cm-2 and records a charge carrier mobility-lifetime product of 1.12 × 10-3 cm2 V-1 among MOF-based X-ray detectors, which are competitive with values for commercially available detectors. These findings demonstrate a rational synthetic approach to designing exciton arrangements to improve the optoelectronic efficiency of semiconductive MOFs.

Promoting ethylene production over a wide potential window on Cu crystallites induced and stabilized via current shock and charge delocalization

Electrochemical CO2 reduction (CO2RR) in a product-orientated and energy-efficient manner relies on rational catalyst design guided by mechanistic understandings. In this study, the effect of conducting support on the CO2RR behaviors of semi-conductive metal-organic framework (MOF) — Cu3(HITP)2 are carefully investigated. Compared to the stand-alone MOF, adding Ketjen Black greatly promotes C2H4 production with a stabilized Faradaic efficiency between 60-70% in a wide potential range and prolonged period. Multicrystalline Cu nano-crystallites in the reconstructed MOF are induced and stabilized by the conducting support via current shock and charge delocalization, which is analogous to the mechanism of dendrite prevention through conductive scaffolds in metal ion batteries. Density functional theory calculations elucidate that the contained multi-facets and rich grain boundaries promote C–C coupling while suppressing HER. This study underlines the key role of substrate-catalyst interaction, and the regulation of Cu crystalline states via conditioning the charge transport, in steering the CO2RR pathway.

High Thermopower in a Zn-Based 3D Semiconductive Metal-Organic Framework.

Conductive metal-organic frameworks (c-MOFs) have drawn increasing attention for their outstanding performance in energy-related applications. However, the majority of reported c-MOFs are based on 2D structures. Synthetic strategies for 3D c-MOFs are under-explored, leaving unrealized functionality in both their structures and properties. Herein we report Zn-HAB, a 3D c-MOF comprised of hexaaminobenzene and Zn(II). Zn-HAB is shown to have microporosity with a band gap of approximately 1.68 eV, resulting in a moderate conductivity of 0.86 mS cm-1 and a high Seebeck coefficient of 200 μV K-1 at 300 K. The power factor of 3.44 nW m-1 K-2 constitutes the first report of the thermoelectric properties of an intrinsically conductive 3D MOF.

Quantum Spin Liquid State in a Two-Dimensional Semiconductive Metal-Organic Framework.

Two-dimensional metal-organic frameworks (2D MOFs) have attracted much attention, as they are the crystalline materials that exhibit both conductivity and microporosity. Numerous efforts have been made to advance their application as chemiresistive sensors or electrochemical capacitors. However, the intrinsic physical properties and spin states of these materials remain poorly understood. Most of these 2D MOFs possess a honeycomb lattice, with a Kagomé lattice arrangement of metal cations. These structural characteristics suggest that these MOFs would be candidates for geometrically frustrated spin systems with unprecedented magnetic phenomena. Herein, by performing magnetic susceptibility and specific heat measurements at an ultralow temperature down to 38mK on a 2D semiconductive MOF, Cu3(HHTP)2, a quantum spin liquid state that arises from the geometrical frustration was suggested. This result illustrates the potential of strongly correlated MOFs as systems with emergent phenomena induced by unusual structural topologies.

2D Semiconducting Metal–Organic Framework Thin Films for Organic Spin Valves

Abstract2D conductive metal–organic frameworks (2D c‐MOFs) feature promising applications as chemiresistive sensors, electrode materials, electrocatalysts, and electronic devices. However, exploration of the spin‐polarized transport in this emerging materials and development of the relevant spintronics have not yet been implemented. In this work, layer‐by‐layer assembly was applied to fabricate highly crystalline and oriented thin films of a 2D c‐MOF, Cu3(HHTP)2, (HHTP: 2,3,6,7,10,11‐hexahydroxytriphenylene), with tunable thicknesses on the La0.67Sr0.33MnO3 (LSMO) ferromagnetic electrode. The magnetoresistance (MR) of the LSMO/Cu3(HHTP)2/Co organic spin valves (OSVs) reaches up to 25 % at 10 K. The MR can be retained with good film thickness adaptability varied from 30 to 100 nm and also at high temperatures (up to 200 K). This work demonstrates the first potential applications of 2D c‐MOFs in spintronics.

2D Semiconducting Metal-Organic Framework Thin Films for Organic Spin Valves.

2D conductive metal-organic frameworks (2D c-MOFs) feature promising applications as chemiresistive sensors, electrode materials, electrocatalysts, and electronic devices. However, exploration of the spin-polarized transport in this emerging materials and development of the relevant spintronics have not yet been implemented. In this work, layer-by-layer assembly was applied to fabricate highly crystalline and oriented thin films of a 2D c-MOF, Cu3 (HHTP)2 , (HHTP: 2,3,6,7,10,11-hexahydroxytriphenylene), with tunable thicknesses on the La0.67 Sr0.33 MnO3 (LSMO) ferromagnetic electrode. The magnetoresistance (MR) of the LSMO/Cu3 (HHTP)2 /Co organic spin valves (OSVs) reaches up to 25 % at 10 K. The MR can be retained with good film thickness adaptability varied from 30 to 100 nm and also at high temperatures (up to 200 K). This work demonstrates the first potential applications of 2D c-MOFs in spintronics.

Direct Radiation Detection by a Semiconductive Metal-Organic Framework.

Semiconductive metal-organic frameworks (MOFs) have attracted extraordinary research interest in recent years; however, electronic applications based on these emerging materials are still in their infancy. Herein, we show that a lanthanide-based semiconductive MOF (SCU-12) can effectively convert X-ray photons to electrical current signals under continuous hard X-ray radiation. The semiconductive MOF-based polycrystalline detection device presents a promising X-ray sensitivity with the value of 23.8 μC Gyair-1 cm-2 under 80 kVp X-ray exposure, competitive with the commercially available amorphous selenium (α-Se) detector. The lowest detectable X-ray dose rate is 0.705 μGy s-1, representing the record value among all X-ray detectors fabricated bypolycrystalline materials. This work discloses the first demonstration of hard radiation detection by semiconductive MOFs, providing a horizon that can guide the synthesis of a new generation of radiation detection materials by taking the advantages of structural designability and property tunability in the MOF system.

Bottom-Up Fabrication of Semiconductive Metal-Organic Framework Ultrathin Films.

Though generally considered insulating, recent progress on the discovery of conductive porous metal-organic frameworks (MOFs) offers new opportunities for their integration as electroactive components in electronic devices. Compared to classical semiconductors, these metal-organic hybrids combine the crystallinity of inorganic materials with easier chemical functionalization and processability. Still, future development depends on the ability to produce high-quality films with fine control over their orientation, crystallinity, homogeneity, and thickness. Here self-assembled monolayer substrate modification and bottom-up techniques are used to produce preferentially oriented, ultrathin, conductive films of Cu-CAT-1. The approach permits to fabricate and study the electrical response of MOF-based devices incorporating the thinnest MOF film reported thus far (10 nm thick).

Porous Field-Effect Transistors Based on a Semiconductive Metal-Organic Framework.

Recently, the emergence of conductive metal-organic frameworks (MOFs) has given great prospects for their applications as active materials in electronic devices. In this work, a high-quality, free-standing conductive MOF membrane was prepared by an air-liquid interfacial growth method. Accordingly, field-effect transistors (FETs) possessing a crystalline microporous MOF channel layer were successfully fabricated for the first time. The porous FETs exhibited p-type behavior, distinguishable on/off ratios, and excellent field-effect hole mobilities as high as 48.6 cm2 V-1 s-1, which is even comparable to the highest value reported for solution-processed organic or inorganic FETs.