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  • A monolithic composite based on zeolite-like metal-organic framework@divinylbenzene polymer separates azeotropic fluorocarbon mixture efficiently.

    Yusuf, Kareem; Shekhah, Osama; Aqel, Ahmad; Alharbi, Seetah; Alghamdi, Ali S; Aljohani, Reem M; Eddaoudi, Mohamed; ALOthman, Zeid A (Journal of chromatography. A, Elsevier BV, 2023-03-15) [Article]
    Organic monolithic columns are mainly used to separate macromolecules; however, many attempts to extend their performance toward small molecules were examined by incorporating micro- and nanoparticles. The incorporation technique enabled utilizing organic monoliths in gas chromatography (GC) for small molecules, which are still scarce. Here, we prepared a composite matrix of capillary monolithic columns of a zeolite-like metal-organic framework with a sodalite topology (sod-ZMOF) and Divinylbenzene polymer (DVB) for GC separations under 0.5 MPa. Relatively short DVB monolithic columns (18 cm long × 0.25 mm i.d.) incorporated with a tiny amount of sod-ZMOF nanoparticles (0.7 and 1.17 wt%) with an average particle size of 225 nm were successfully fabricated and used to separate linear alkanes and polar probes mixtures with increasing resolution up to 3.7 and 5.1 times, respectively, compared to a blank DVB monolithic column. A high-performance separation of linear alkanes series mixture (methane to decane) was exhibited in less than 2 min. McReynolds constants revealed that sod-ZMOF provided the composite monolith with a nonpolar character yielding a negative average polarity value smaller than the standard squalene column. An Excellent retention time of pentane and octane day-to-day reproducibility was achieved during 16 days and over more than 500 runs with RSD% of 2.25% and 3.3% using a composite monolithic column with 5 mg mL−1 sod-ZMOF (5-ZMOF@DVB). In addition, a qualitative determination of the gas mixture content of three commercially available Lighter gas cartridges was performed via the 5-ZMOF@DVB column. Finally, successfully separating an azeotropic freon mixture of difluoromethane (R-32) and pentafluoroethane (R-125) was achieved with a selectivity of up to 4.84. A further thermodynamic study related the preferential adsorption of R-125 to entropic factors rather than enthalpic while trapping inside ZMOF pores. This work sheds light on utilizing the infinite diversity of MOFs and combining their properties with high permeability and easily fabricated organic monoliths for GC separations of light molecules and gasses. Furthermore, the study highlights the role of GC as an easy and fast approach for the preliminary evaluation of the separation efficiency of porous polymers.
  • Copper Organometallic Iodide Arrays for Efficient X-ray Imaging Scintillators

    Wang, Hong; Wang, Jian-Xin; Song, Xin; He, Tengyue; Zhou, Yang; Shekhah, Osama; Gutierrez Arzaluz, Luis; Bayindir, Mehmet; Eddaoudi, Mohamed; Bakr, Osman; Mohammed, Omar F. (ACS Central Science, American Chemical Society (ACS), 2023-03-10) [Article]
    Lead-free organic metal halide scintillators with low-dimensional electronic structures have demonstrated great potential in X-ray detection and imaging due to their excellent optoelectronic properties. Herein, the zero-dimensional organic copper halide (18-crown-6)2Na2(H2O)3Cu4I6 (CNCI) which exhibits negligible self-absorption and near-unity green-light emission was successfully deployed into X-ray imaging scintillators with outstanding X-ray sensitivity and imaging resolution. In particular, we fabricated a CNCI/polymer composite scintillator with an ultrahigh light yield of ∼109,000 photons/MeV, representing one of the highest values reported so far for scintillation materials. In addition, an ultralow detection limit of 59.4 nGy/s was achieved, which is approximately 92 times lower than the dosage for a standard medical examination. Moreover, the spatial imaging resolution of the CNCI scintillator was further improved by using a silicon template due to the wave-guiding of light through CNCI-filled pores. The pixelated CNCI-silicon array scintillation screen displays an impressive spatial resolution of 24.8 line pairs per millimeter (lp/mm) compared to the resolution of 16.3 lp/mm for CNCI-polymer film screens, representing the highest resolutions reported so far for organometallic-based X-ray imaging screens. This design represents a new approach to fabricating high-performance X-ray imaging scintillators based on organic metal halides for applications in medical radiography and security screening.
  • A Tailored COF for Visible-Light Photosynthesis of 2,3-Dihydrobenzofurans

    Parvatkar, Prakash Tukaram; Kandambeth, Sharath; Shaikh, Aslam; Nadinov, Issatay; Yin, Jun; Kale, Vinayak Swamirao; Healing, George; Emwas, Abdul-Hamid M.; Shekhah, Osama; Alshareef, Husam N.; Mohammed, Omar F.; Eddaoudi, Mohamed (Journal of the American Chemical Society, American Chemical Society (ACS), 2023-02-24) [Article]
    Heterogeneous photocatalysis is considered as an ecofriendly and sustainable approach for addressing energy and environmental persisting issues. Recently, heterogeneous photocatalysts based on covalent organic frameworks (COFs) have gained considerable attention due to their remarkable performance and recyclability in photocatalytic organic transformations, offering a prospective alternative to homogeneous photocatalysts based on precious metal/organic dyes. Herein, we report Hex-Aza-COF-3 as a metal-free, visible-light-activated, and reusable heterogeneous photocatalyst for the synthesis of 2,3-dihydrobenzofurans, as a pharmaceutically relevant structural motif, via the selective oxidative [3+2] cycloaddition of phenols with olefins. Moreover, we demonstrate the synthesis of natural products (±)-conocarpan and (±)-pterocarpin via the [3+2] cycloaddition reaction as an important step using Hex-Aza-COF-3 as a heterogeneous photocatalyst. Interestingly, the presence of phenazine and hexaazatriphenylene as rigid heterocyclic units in Hex-Aza-COF-3 strengthens the covalent linkages, enhances the absorption in the visible region, and narrows the energy band, leading to excellent activity, charge transport, stability, and recyclability in photocatalytic reactions, as evident from theoretical calculations and real-time information on ultrafast spectroscopic measurements.
  • Tunable Photoinduced Charge Transfer at the Interface between Benzoselenadiazole-Based MOF Linkers and Thermally Activated Delayed Fluorescence Chromophore

    Alomar, Shorooq A.; Gutierrez Arzaluz, Luis; Nadinov, Issatay; He, Ru; Wang, Xiaodan; Wang, Jian-Xin; Jia, Jiangtao; Shekhah, Osama; Eddaoudi, Mohamed; Alshareef, Husam N.; Schanze, Kirk; Mohammed, Omar F. (The Journal of Physical Chemistry B, American Chemical Society (ACS), 2023-02-21) [Article]
    Structural modifications to molecular systems that lead to the control of photon emission processes at the interfaces between photoactive materials play a key role in the development of fluorescence sensors, X-ray imaging scintillators, and organic light-emitting diodes (OLEDs). In this work, two donor–acceptor systems were used to explore and reveal the effects of slight changes in chemical structure on interfacial excited-state transfer processes. A thermally activated delayed fluorescence (TADF) molecule was chosen as the molecular acceptor. Meanwhile, two benzoselenadiazole-core MOF linker precursors, Ac-SDZ and SDZ, with the presence and absence of a C≡C bridge, respectively, were carefully chosen as energy and/or electron-donor moieties. We found that the SDZ -TADF donor–acceptor system exhibited efficient energy transfer, as evidenced by steady-state and time-resolved laser spectroscopy. Furthermore, our results demonstrated that the Ac-SDZ–TADF system exhibited both interfacial energy and electron transfer processes. Femtosecond-mid-IR (fs-mid-IR) transient absorption measurements revealed that the electron transfer process takes place on the picosecond timescale. Time-dependent density functional theory (TD-DFT) calculations confirmed that photoinduced electron transfer occurred in this system and demonstrated that it takes place from C≡C in Ac-SDZ to the central unit of the TADF molecule. This work provides a straightforward way to modulate and tune excited-state energy/charge transfer processes at donor–acceptor interfaces.
  • A zeolite-like Metal-Organic Framework Based Membrane for Reverse Selective Hydrogen Separation and Butane Isomers Sieving

    Chernikova, Valeriya; Shekhah, Osama; Belmabkhout, Youssef; Karunakaran, Madhavan; Eddaoudi, Mohamed (Angewandte Chemie International Edition, Wiley, 2023-02-10) [Article]
    Here, the fabrication of a defect-free membrane that is based on a zeolite-like metal-organic framework (ZMOF) with the underlying ana topology is reported. The unique ana-ZMOF structure provides high degree of pore connectivity, which is reflected by the fast transport of gases. Prominently, it offers an optimum pore-aperture size, affording notable sieving selectivity for butane/isobutane, and optimal pore energetics for reverse CO2/H2 separation. This emphasize the potential for the application of pure MOF membranes, paving the way to more sustainability of energy resources.
  • A CO2-recognition metal-organic framework membrane for continuous carbon capture

    Zhou, Sheng; Shekhah, Osama; Jin, Tian; Jia, Jiangtao; Datta, Shuvo; Bhatt, Prashant; Eddaoudi, Mohamed (Chem, Elsevier BV, 2023-02-09) [Article]
    The steady removal of carbon dioxide (CO2) from diverse gas streams is a critical step toward achieving the blueprint of carbon neutrality and clean energy production. However, the associated energy and capital inputs are considerably high, necessitating the development of effective technologies for CO2 separation. Here, we report a special CO2-recognition membrane based on a fluorinated metal-organic framework (KAUST-7) for efficient CO2 capture from various mixtures including CO2/H2, CO2/CH4, and CO2/N2. Uniquely, the appropriate CO2 affinity cooperating with the confined aperture of KAUST-7 enables the membrane with the right orientation to be nearly only permeable to CO2, showing unprecedented CO2 separation selectivity over both smaller (H2) and larger (N2, CH4) molecules. The extraordinary performance is maintained after treatment with corrosive hydrogen sulfide or humid atmospheres, swing temperatures or pressures, and long-term operations, pinpointing the potential for high-throughput CO2 capture in a continuous mode.
  • Institution of Metal–Organic Frameworks as a Highly Sensitive and Selective Layer In-Field Integrated Soil-Moisture Capacitive Sensor

    Alsadun, Norah Sadun; Surya, Sandeep Goud; Patle, Kamlesh; Palaparthy, Vinay S.; Shekhah, Osama; Salama, Khaled N.; Eddaoudi, Mohamed (ACS Applied Materials & Interfaces, American Chemical Society (ACS), 2023-01-20) [Article]
    The ongoing global industrialization along with the notable world population growth is projected to challenge the global environment as well as pose greater pressure on water and food needs. Foreseeably, an improved irrigation management system is essential and the quest for refined chemical sensors for soil-moisture monitoring is of tremendous importance. Nevertheless, the persisting challenge is to design and construct stable materials with the requisite sensitivity, selectivity, and high performance. Here, we report the introduction of porous metal–organic frameworks (MOFs), as the receptor layer, in capacitive sensors to efficiently sense moisture in two types of soil. Namely, our study unveiled that Cr-soc-MOF-1 offers the best sensitivity (≈24,000 pF) among the other tested MOFs for any given range of soil-moisture content, outperforming several well-known oxide materials. The corresponding increase in the sensitivities for tested MOFs at 500 Hz are ≈450, ≈200, and ≈30% for Cr-soc-MOF-1, Al-ABTC-soc-MOF, and Zr-fum-fcu-MOF, respectively. Markedly, Cr-soc-MOF-1, with its well-known water capacity, manifests an excellent sensitivity of ≈450% in clayey soil, and the analogous response time was 500 s. The noted unique sensing properties of Cr-soc-MOF-1 unveils the great potential of MOFs for soil-moisture sensing application.
  • Energy- and carbon-efficient CO2/CO electrolysis to multicarbon products via asymmetric ion migration–adsorption

    Ozden, Adnan; Li, Jun; Kandambeth, Sharath; Li, Xiao-yan; Liu, Shijie; Shekhah, Osama; Ou, Pengfei; Zou Finfrock, Y.; Wang, Ya-Kun; Alkayyali, Tartela; García de Arquer, F Pelayo; Kale, Vinayak Swamirao; Bhatt, Prashant; Ip, Alexander H.; Eddaoudi, Mohamed; Sargent, E.; Sinton, David (Nature Energy, Springer Science and Business Media LLC, 2023-01-12) [Article]
    Carbon dioxide/monoxide (CO2/CO) electrolysis provides a means to convert emissions into multicarbon products. However, impractical energy and carbon efficiencies limit current systems. Here we show that these inefficiencies originate from uncontrolled gas/ion distributions in the local reaction environment. Understanding of the flows of cations and anions motivated us to seek a route to block cation migration to the catalyst surface—a strategy we instantiate using a covalent organic framework (COF) in bulk heterojunction with a catalyst. The π-conjugated hydrophobic COFs constrain cation (potassium) diffusion via cation–π interactions, while promoting anion (hydroxide) and gaseous feedstock adsorption on the catalyst surface. As a result, a COF-mediated catalyst enables electrosynthesis of multicarbon products from CO for 200 h at a single-pass carbon efficiency of 95%, an energy efficiency of 40% and a current density of 240 mA cm−2.
  • Fluorinated Covalent Organic Framework as a Positive Tribo-Material for High-Performance Triboelectric Nanogenerators

    Shi, Lin; Kale, Vinayak Swamirao; Tian, Zhengnan; Xu, Xiangming; Lei, Yongjiu; Kandambeth, Sharath; Wang, Yizhou; Parvatkar, Prakash Tukaram; Shekhah, Osama; Eddaoudi, Mohamed; Alshareef, Husam N. (Advanced Functional Materials, Wiley, 2023-01-12) [Article]
    Along with the increasingly wide application of intelligent electronics, triboelectric nanogenerator (TENG), as a promising sustainable micro-power source has attracted considerable attention recently. However, most of the reported research focuses on negative triboelectric materials, while research on alternative positive tribo-layers is still limited. In this study, a new highly fluorinated covalent organic framework (COF) Tp-TFAB is successfully synthesized and utilized as positive triboelectric materials for high-performance TENGs. Unusually, compared with the non-fluorinated Tp-TAPB COF, both the pristine Tp-TFAB COF and corresponding hybrid films with polyvinyl alcohol (PVA) based TENGs demonstrate much higher triboelectric performance. Especially, a PVC-PVA/FTC TENG composed of polyvinyl chloride (PVC) and hybrid PVA/Tp-TFAB (PVA/FTC) films reveal much superior triboelectric performance with a short-circuit current density of 26.34 mA m−2, a transferred charge density of 148.5 µC m−2, and a maximum peak power density of 8.24 W m−2, nearly six times higher than that of the PVC-PVA TENG. Detailed investigations revealed that the fluorinated Tp-TFAB COF has enhanced electron donating ability, which significantly boosts the triboelectric output of TENGs. This study provides an effective strategy of chemically designing and synthesizing new alternative triboelectric materials, which will pave the way to significantly enhance the triboelectric performance of TENGs.
  • A Symmetric Aqueous Magnesium Ion Supercapattery Based on Covalent Organic Frameworks

    Zou, Guodong; Tian, Zhengnan; Kale, Vinayak Swamirao; Wang, Wenxi; Kandembeth, Sharath; Cao, Zhen; Guo, Jing; Czaban-Jóźwiak, Justyna; Cavallo, Luigi; Shekhah, Osama; Eddaoudi, Mohamed; Alshareef, Husam N. (Advanced Energy Materials, Wiley, 2022-12-29) [Article]
    Aqueous magnesium ion-based batteries have attracted significant research interest due to the two-electron transfer process, small cation radius, low reduction potential as well as the inert hydrogen evolution reaction. However, the high surface charge density of divalent Mg2+ ions results in sluggish solid-state diffusion kinetics, which significantly limits the number of host materials suitable for effective Mg2+ ion storage. Here, for the first time, covalent organic frameworks (COFs) are explored as host materials for high-rate aqueous Mg2+ ion batteries. Combining electrochemical and spectral characterization with theoretical simulation, a synergistic charge storage mechanism involving the reaction of nitrogen and oxygen bridged by Mg2+ ions is revealed. Using electrochemical analysis, it is shown that the Mg2+ ion diffusion kinetics are dominated by the surface pseudocapacitive behavior in COFs, which achieves a favorable rate performance and durable cyclic stability. This work offers a new perspective on the storage of Mg2+ ions in COF host materials.
  • Fifth international conference on materials and environmental science: Role of new materials in sustainable development

    Touzani, R.; Hammouti, B.; Eddaoudi, Mohamed (Materials Today: Proceedings, Elsevier BV, 2022-12-02) [Article]
    The Fifth International Conference on Materials and Environmental Science (ICMES20221), is an interdisciplinary platform to promote a multi-sectoral and collaborative approach in the field of development of new and innovative approaches in materials, their applications in energy and renewable energy, environmental science, sustainable development, health, biotechnology and electrical engineering. The scientific committee of ICMES2022 agreed that the health session was the priority since the Covid19 pandemic still constitutes a Public Health Emergency of International Concern. There are many multifunctional materials available by the advent of nanotechnology, ranging from carbon nanotubes, graphene, inorganic nanoparticles, conducting polymers, 2D materials, CO2 material capture, etc… Materials science Conference is an event that brings together leading researchers spanning the field of materials science and engineering to present and discuss cutting edge research with other experts in the field: exchanging ideas to advance current understanding towards the future of materials science.
  • Unveiling Chemically Robust Bimetallic Squarate-Based Metal–Organic Frameworks for Electrocatalytic Oxygen Evolution Reaction

    Kandambeth, Sharath; Kale, Vinayak Swamirao; Fan, Dong; Bau, Jeremy; Bhatt, Prashant; Zhou, Sheng; Shkurenko, Aleksander; Rueping, Magnus; Maurin, Guillaume; Shekhah, Osama; Eddaoudi, Mohamed (Advanced Energy Materials, Wiley, 2022-11-18) [Article]
    Here, this work reports an innovative strategy for the synthesis of chemically robust metal–organic frameworks (MOFs), and applies them as catalysts for the electrocatalytic oxygen evolution reaction (OER). A bimetallic squarate-based MOF (Sq-MOF) with a zbr topology serves as an excellent platform for electrocatalytic OER owing to its open porous structure, high affinity toward water, and presence of catalytically active 1D metal hydroxide strips. By regulating the Ni2+ content in a bimetallic squarate MOF system, the electrochemical structural stability toward OER can be improved. The screening of various metal ratios demonstrates that Ni3Fe1 and Ni2Fe1 Sq-zbr-MOFs show the best performance for electrocatalytic OER in terms of catalytic activity and structural stability. Ni2Fe1 Sq-zbr-MOF shows a low overpotential of 230 mV (at 10 mA cm−2) and a small Tafel slope of 37.7 mV dec−1, with an excellent long-term electrochemical stability for the OER. Remarkably, these overpotential values of Ni2Fe1 Sq-zbr-MOF are comparable with those of the best-performing layered double hydroxide (LDH) systems and outperforms the commercially available noble-metal-based RuO2 catalyst for OER under identical operational conditions.
  • Toward Reduced CO2 Emissions from Vehicles: Onboard Capture and Storage System Using Metal-Organic Frameworks

    Pezzella, Giuseppe; Bhatt, Prashant; Alhaji, Abdulhadi; Ramirez, Adrian; Grande, Carlos A.; Gascon, Jorge; Eddaoudi, Mohamed; Sarathy, Mani (Research Square Platform LLC, 2022-11-17) [Preprint]
    The transportation sector is among the largest contributors to carbon dioxide (CO2) emissions and demands immediate action. Although electrification is a promising technology to decarbonize light-duty vehicles, it has limited potential when applied to heavy trucks due to their longer travel distances and weight constraints. Hence, possible mitigation pathways must be identified to lower trucks’ carbon footprint. In this work, we propose an onboard post-combustion capture and storage system on heavy-duty freight vehicles using two state-of-the-art metal-organic frameworks (MOFs) with high CO2 selectivity and high-storage-capacity, respectively. We selected KAUST-7 as the capturing material because of its high stability and selectivity toward CO2 even in humid conditions; while Al-soc-MOF-1 as a CO2 storing material for its high gravimetric and volumetric CO2 uptake between 10 and 50 bar. Our solution aimed to reduce heavy-duty vehicle CO2 emissions by at least 50% and achieve above 95% CO2 purity at the storage point. First, we measured and modeled KAUST-7’s thermodynamic and kinetic properties, then we simulated and optimized the process conditions for the carbon capture system in response to dynamic engine behavior. Additionally, we minimized the capture and storage mass, offering as result innovative methods to mitigate carbon emissions in the heavy-duty freight industry.
  • Nitrogen Reduction to Ammonia by a Phosphorus-Nitrogen PN3PMo(V) Nitride Complex: Significant Enhancement via Ligand Post-Modification

    Han, Delong; Chakraborty, Priyanka; Huang, Mei-Hui; Yang, Li; Huang, Hao; Goncalves, Theo; Emwas, Abdul-Hamid M.; Lai, Zhiping; He, Jr-Hau; Shkurenko, Aleksander; Eddaoudi, Mohamed; Huang, Kuo-Wei (CCS Chemistry, Chinese Chemical Society, 2022-11-11) [Article]
    Efforts to develop organometallic complexes for catalytic nitrogen reduction have seen significant progress in recent years. However, the strategies for improving the activity of the homogenous catalysts have been mainly focused on alternating ligands and metals so far. Herein, we report that the activity and stability of a PN3P-Mo pincer complex ( 2) toward dinitrogen (N2) reduction were greatly enhanced through the post-modification of the PN3P pincer framework of its parent complex ( 1). A high ratio of NH3/Mo (3525) was achieved in the presence of SmI2 as a reductant. In sharp contrast, 1 only afforded an NH3/Mo ratio of 21. Moreover, since supported by the anionic pincer ligand, 2 furnished a high oxidation state Mo(V) nitride complex as a plausible key intermediate in the catalytic process via N2-cleavage, suggesting a catalytic cycle that may involve different oxidation states (II/V) from those with 10-π electron configuration in the literature.
  • Metal–Organic Frameworks Meet Molecularly Imprinted Polymers: Insights and Prospects for Sensor Applications

    Lahcen, Abdellatif Ait; Surya, Sandeep Goud; Beduk, Tutku; Vijjapu, Mani Teja; Lamaoui, Abderrahman; Durmus, Ceren; Timur, Suna; Shekhah, Osama; Mani, Veerappan; Amine, Aziz; Eddaoudi, Mohamed; Salama, Khaled N. (ACS Applied Materials & Interfaces, American Chemical Society (ACS), 2022-10-31) [Article]
    The use of porous materials as the core for synthesizing molecularly imprinted polymers (MIPs) adds significant value to the resulting sensing system. This review covers in detail the current progress and achievements regarding the synergistic combination of MIPs and porous materials, namely metal/covalent–organic frameworks (MOFs/COFs), including the application of such frameworks in the development of upgraded sensor platforms. The different processes involved in the synthesis of MOF/COF-MIPs are outlined, along with their intrinsic properties. Special attention is paid to debriefing the impact of the morphological changes that occur through the synergistic combination compared to those that occur due to the individual entities. Thereafter, the strategies used for building the sensors, as well as the transduction modes, are overviewed and discussed. This is followed by a full description of research advances for various types of MOF/COF-MIP-based (bio)sensors and their applications in the fields of environmental monitoring, food safety, and pharmaceutical analysis. Finally, the challenges/drawbacks, as well as the prospects of this research field, are discussed in detail.
  • Reticular chemistry for the rational design of mechanically robust mesoporous merged-net metal-organic frameworks

    Jiang, Hao; Moosavi, Seyed Mohamad; Czaban-Jozwiak, Justyna; Torre, Bruno; Shkurenko, Aleksander; Ameur, Zied Ouled; Jia, Jiangtao; Alsadun, Norah Sadun; Shekhah, Osama; Di Fabrizio, Enzo M.; Smit, Berend; Eddaoudi, Mohamed (Matter, Elsevier BV, 2022-10-31) [Article]
    Access to metal-organic frameworks (MOFs) with enhanced mechanical stability is key to their successful deployment in practical applications. However, the high porosity of the material often affects mechanical stability. In this article, to achieve highly porous MOFs with enhanced mechanical stability, we explored the merged-net approach where two relatively fragile frameworks were merged into a robust MOF structure. We demonstrate the effectiveness of this approach by computationally evaluating mechanical properties of sph-MOFs with varying lengths of linkers. Prominently, we pinpoint the significance of triangular rigidity on the robustness of large-pore MOFs and, subsequently, designed and synthesized a rare earth (RE)-based RE-sph-MOF-5 by the reticulation of hexanuclear RE clusters, tritopic linkers, and unprecedentedly large planar hexatopic linkers containing 19 phenyl rings. The mechanical properties of sph-MOFs were characterized and quantified using amplitude-frequency modulation (AM-FM) bimodal atomic force microscopy (AFM) analyses. Markedly, the mesoporous RE-sph-MOF-5 expresses high mechanical stability despite its large mesoporous cavities.
  • Heavy-atom engineering of thermally activated delayed fluorophores for high-performance X-ray imaging scintillators

    Wang, Jian-Xin; Gutierrez Arzaluz, Luis; Wang, Xiaojia; He, Tengyue; Zhang, Yuhai; Eddaoudi, Mohamed; Bakr, Osman; Mohammed, Omar F. (Nature Photonics, Springer Science and Business Media LLC, 2022-10-27) [Article]
    The architectural design and fabrication of low-cost and reliable organic X-ray imaging scintillators with high light yield, ultralow detection limits and excellent imaging resolution is becoming one of the most attractive research directions for chemists, materials scientists, physicists and engineers due to the devices’ promising scientific and applied technological implications. However, the optimal balance among X-ray absorption capability, exciton utilization efficiency and photoluminescence quantum yield of organic scintillation materials is extremely difficult to achieve because of several competitive non-radiative processes, including intersystem crossing and internal conversion. Here we introduced heavy atoms (Cl, Br and I) into thermally activated delayed fluorescence (TADF) chromophores to significantly increase their X-ray absorption cross-section and maintaining their unique TADF properties and high photoluminescence quantum yield. The X-ray imaging screens fabricated using TADF-Br chromophores exhibited highly improved X-ray sensitivity and imaging resolution compared with the TADF-H counterpart. More importantly, the high X-ray imaging resolution of >18.0 line pairs per millimetre achieved from the TADF-Br screen exceeds most reported organic and conventional inorganic scintillators. This study could help revive research on organic X-ray imaging scintillators and pave the way towards exciting applications for radiology and security screening.
  • Triplet-triplet energy-transfer-based transparent X-ray imaging scintillators

    Wang, Jian-Xin; Dutta, Indranil; Yin, Jun; He, Tengyue; Gutierrez Arzaluz, Luis; Bakr, Osman; Eddaoudi, Mohamed; Huang, Kuo-Wei; Mohammed, Omar F. (Matter, Elsevier BV, 2022-10-20) [Article]
    In this work, we fabricated a highly efficient and reabsorption-free transparent X-ray imaging scintillator with high performance using an efficient triplet-triplet energy transfer strategy between thermally activated delayed fluorophore (TADF-Br) and iridium organometallic complex (Ir-OMC). Steady-state and ultrafast time-resolved experiments—supported by high-level density functional theory calculations—clearly demonstrate that efficient triplet-triplet energy transfer from TADF-Br with a high X-ray absorption cross-section to emissive Ir-OMC can be achieved. Such high efficiency of interfacial triplet energy transfer and the heavy atoms in both the donor and acceptor led to a remarkable enhancement in triplet-state radioluminescence upon X-ray irradiation. The fabricated X-ray imaging scintillator achieved an X-ray imaging resolution of 19.8 lp mm−1, exceeding the resolution of most reported organic and organometallic scintillation screens.
  • High-rate and Selective CO2 Electrolysis to Ethylene via Metal-Organic Framework-augmented CO2 Availability

    Nam, Dae-Hyun; Shekhah, Osama; Ozden, Adnan; McCallum, Christopher; Li, Fengwang; Wang, Xue; Lum, Yanwei; Lee, Taemin; Li, Jun; Wicks, Joshua; Johnston, Andrew; Sinton, David; Eddaoudi, Mohamed; Sargent, E. (Advanced Materials, Wiley, 2022-10-17) [Article]
    High-rate carbon dioxide (CO2)-to-ethylene (C2H4) conversion in the CO2 reduction reaction (CO2RR) requires fine control over the phase boundary of the gas diffusion electrode (GDE) to overcome the limit of CO2 solubility in aqueous electrolyte. Here, we present a metal-organic framework (MOF)-functionalized GDE design, one based on a catalysts:MOFs:hydrophobic substrate materials layered architecture, that leads to high-rate and selective C2H4 production in flow cell and membrane electrode assembly (MEA) electrolyzers. We find, using electroanalysis and operando X-ray absorption spectroscopy (XAS), that MOF-induced organic layers in GDEs augment local CO2 concentration near the active sites of the Cu catalysts. We use MOFs with different CO2 adsorption abilities and vary the stacking ordering of MOFs in the GDE. While sputtered Cu on PTFE (Cu/PTFE) exhibited 43% C2H4 Faradaic efficiency (FE) at a current density of 200 mA/cm2 in a flow cell, 49% C2H4 FE at 1 A/cm2 was achieved on MOF-augmented GDEs in CO2RR. We further evaluate MOF-augmented GDEs in MEA electrolyzer, achieving a C2H4 partial current density of 220 mA/cm2 for CO2RR and 121 mA/cm2 for carbon monoxide reduction reaction (CORR), representing 2.7-fold and 15-fold improvement in C2H4 production rate, compared to those obtained on bare Cu/PTFE.
  • Advances in metal–organic framework-based membranes

    Cheng, Youdong; Datta, Shuvo Jit; Zhou, Sheng; Jia, Jiangtao; Shekhah, Osama; Eddaoudi, Mohamed (Chemical Society Reviews, Royal Society of Chemistry (RSC), 2022-09-07) [Article]
    Membrane-based separations have garnered considerable attention owing to their high energy efficiency, low capital cost, small carbon footprint, and continuous operation mode. As a class of highly porous crystalline materials with well-defined pore systems and rich chemical functionalities, metal–organic frameworks (MOFs) have demonstrated great potential as promising membrane materials over the past few years. Different types of MOF-based membranes, including polycrystalline membranes, mixed matrix membranes (MMMs), and nanosheet-based membranes, have been developed for diversified applications with remarkable separation performances. In this comprehensive review, we first discuss the general classification of membranes and outline the historical development of MOF-based membranes. Subsequently, particular attention is devoted to design strategies for MOF-based membranes, along with detailed discussions on the latest advances on these membranes for various gas and liquid separation processes. Finally, challenges and future opportunities for the industrial implementation of these membranes are identified and outlined with the intent of providing insightful guidance on the design and fabrication of high-performance membranes in the future.

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