Recent Submissions

  • Sintering-free catalytic ammonia cracking by vertically standing 2D porous framework supported Ru nanocatalysts

    Kim, Seok-Jin; Nguyen, Thien Si; Mahmood, Javeed; Yavuz, Cafer T. (Chemical Engineering Journal, Elsevier BV, 2023-03-18) [Article]
    Catalytic ammonia decomposition enables ammonia to be a hydrogen gas carrier for a carbon-free fuel economy. The challenge is to obtain high conversion yields and rates at low temperatures for a prolonged time. A promising approach is to engineer a catalyst support to minimize deleterious effects like sintering. Here, we compared a conventional 2D planar porous framework support with a vertically standing 2D structure to ascertain the effects of support geometry on the catalytic performance. The catalysts were made by loading ruthenium (Ru) nanoparticles onto the structures, and the catalytic activities were monitored by varying the ammonia (NH3) feeding rate and reaction temperature. Unlike the planar version, the vertically standing 2D support prevented nanoparticle aggregation, retained the original nanoparticle size, and showed an excellent hydrogen production rate (95.17 mmol gRu-1min-1) at a high flow rate of 32,000 ml gcat-1h-1 at a temperature of 450 ℃.
  • Fouling of Polyalkylmethylsiloxane Composite Membranes during Pervaporation Separation of ABE-Fermentation Mixtures

    Rokhmanka, Tatyana N.; Grushevenko, Evgenia A.; Arapova, Olga V.; Bondarenko, Galina N.; Golubev, George S.; Borisov, Ilya L.; Volkov, Alexey V. (Applied Sciences, MDPI AG, 2023-03-16) [Article]
    Production of bio-alcohols is one of the approaches used in the development of alternative energy. Pervaporation is a promising option for the separation of bio-alcohols from the fermentation mixture. A serious problem in the process of continuous extraction of biobutanol from the fermentation broth is the contamination of the membrane, which leads to a decrease in its permeability over time. In this work, the transport properties of composite membranes based on polyheptylmethylsiloxane (PHeptMS), polydecylmethylsiloxane (PDecMS), and a commercial membrane MDK-3 were studied during separation of a real ABE-fermentation broth in vacuum pervaporation mode. The study was performed before and after continuous contact of the membranes with the fermentation broth for one month. Visually and by scanning electron spectroscopy, the presence of membrane surface residue and its effect on the wettability of the membrane selective layer by the components of the ABE broth were determined. The sediment composition was evaluated by energy dispersive analysis and infrared spectroscopy. According to the pervaporation separation of the ABE-broth using PHeptMS, PDecMS, and MDK-3 membranes, the butanol flux was 0.029, 0.012, and 0.054 kg/(m2·h), respectively. The butanol-water partition factor was 41, 22, and 13 for PHeptMS, PDecMS, and MDK-3, respectively. After one month of incubation of the membranes in ABE-fermentation broth during the separation of the model mixture, a decrease of 10 and 5% in permeate flux and separation factor, respectively, was observed for all membranes. Temperature dependences (30–60 °C) of permeate flux, permeability, and selectivity were obtained for the membranes after clogging. The most promising in terms of minimal negative changes as a result of fouling was demonstrated by the PHeptMS membrane. For it, the clogging dynamics during separation of the real fermentation broth for 216 h were investigated. Two characteristic steps of decrease in transport and separation properties were observed, after 28 and 150 h of the experiment. After 216 h of experiment, a 1.28-fold decrease in total flux through the membrane, a 9% decrease in butanol permeability, and a 10% decrease in n-butanol selectivity were found for PHeptMS.
  • Ultra-Highly Active Ni-Doped MOF-5 Heterogeneous Catalysts for Ethylene Dimerization.

    Chen, Cailing; Meng, Lingkun; Alalouni, Mohammed R; Dong, Xinglong; Wu, Zhi-Peng; Zuo, Shouwei; Zhang, Huabin (Small (Weinheim an der Bergstrasse, Germany), Wiley, 2023-03-15) [Article]
    Here, an ultra-highly active Ni-MOF-5 catalyst with high Ni loading for ethylene dimerization is reported. The Ni-MOF-5 catalysts are synthesized by a facile one-pot co-precipitation method at room temperature, where Ni2+ replaces Zn2+ in MOF-5. Unlike Zn2+ with tetrahedral coordination in MOF-5, Ni2+ is coordinated with extra solvent molecules except for four-oxygen from the framework. After removing coordinated solvent molecules, Ni-MOF-5 achieves an ethylene turnover frequency of 352 000 h−1, corresponding to 9040 g of product per gram of catalyst per hour, at 35 °C and 50 bar, far exceeding the activities of all reported heterogeneous catalysts. The high Ni loading and full exposure structure account for the excellent catalytic performance. Isotope labeling experiments reveal that the catalytic process follows the Cossee–Arlman mechanism, rationalizing the high activity and selectivity of the catalyst. These results demonstrate that Ni-MOF-5 catalysts are very promising for industrial catalytic ethylene dimerization.
  • 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.
  • Nanometer-thick crystalline and amorphous zeolitic imidazolate framework films for membrane and patterning applications

    Liu, Qi; Miao, Yurun; Villalobos, Luis Francisco; Li, Shaoxian; Babu, Deepu J.; Chen, Cailing; Chi, Heng-Yu; Vahdat, Mohammad Tohidi; Hao, Jian; Song, Shuqing; Han, Yu; Tsapatsis, Michael; Agrawal, Kumar Varoon (Research Square Platform LLC, 2023-03-14) [Preprint]
    Zeolitic imidazolate frameworks (ZIFs) are a subset of metal-organic frameworks (MOFs) with more than 200 characterized crystalline and amorphous networks made of divalent transition metal centers (e.g., Zn2+ and Co2+) linked by imidazolate linkers. ZIF thin films have been pursued intensively motivated by the desire to prepare membranes for selective gas and liquid separations. To achieve membranes with high throughput, as in Å-scale biological channels with nanometer-scale pathlengths, ZIF films with the minimum possible thickness, down to just one unit cell, are highly desired. Control of ZIF film thickness at the 10-nm-scale may also enable emerging, MOF-inspired, applications including patterned crystalline MOF films, and amorphous organic-inorganic resists for high-resolution electron-beam (e-beam) and extreme UV (EUV) lithography. However, the state-of-the-art methods yield ZIF films with thicknesses exceeding 40 nanometers. Here, we report a deposition method from ultra-dilute precursor mixtures that within minutes yields uniform ZIF deposits with nm-scale thickness control. On crystalline substrate such as graphene, two-dimensional crystalline ZIF (2DZIF) film with thickness of a unit-cell could be achieved, which composed of a six-membered zincimidazolate coordination ring enabling record-high H2 permselective separation performance. Deposition under identical conditions on amorphous substrates yields macroscopically smooth amorphous ZIF (aZIF) films, which can be used as negative- and positive-tone resists yielding pattern features down to 20 nm. The method reported here will likely accelerate the development of 2D crystalline and ultrathin amorphous MOF films for applications ranging from separation membranes to sensors and patterning for microelectronic applications.
  • 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.
  • Porous liquid metal-organic frameworks with selectively high gas solubility

    Ma, Jie; He, Libo; Yang, Ruilu; Wang, Dechao; Qu, Danyao; Su, Chen; Pang, Haili; Wu, Weiwei; Li, Peipei; Zhang, Lu; Liu, Xiaowei (Fuel, Elsevier BV, 2023-03-08) [Article]
    Porous liquid metal–organic frameworks (MOFs) have recently been discovered rather promising for gas absorption and separation in practical chemical industry processes. In this work, we successfully fabricated a kind of MOF-based porous liquid (i.e., UIO-66-PL) by dispersing the hydrophilic porous filler of UIO-66-NH2 nanoparticles into a specific hydrophilic ionic liquid (IL, [HEMIM][DCA]) through the wet-impregnation method. The obtained UIO-66-PL was a kind of stable porous liquid with well-maintained permanent porosity and liquid-like behavior at room temperature. More importantly, this UIO-66-PL has larger gas absorption capacities than its reference IL hindered solvent as the well-preserved permanent porosity could act as free void space for gas accommodation. Also, IL could serve as a selective gate for target gas to the permanent porosity within UIO-66-PL, i.e., the majority of the permanent porosity in UIO-66-PL is inaccessible to nitrogen, but available for carbon dioxide, demonstrating that this UIO-66-PL could function as a type of fluid selective gas sorbent with high target gas solubility.
  • Salts as Additives: A Route to Improve Performance and Stability of n-Type Organic Electrochemical Transistors

    Ohayon, David; Flagg, Lucas Q.; Giugni, Andrea; Wustoni, Shofarul; Li, Ruipeng; Hidalgo, Tania C.; Emwas, Abdul-Hamid M.; Sheelamanthula, Rajendar; McCulloch, Iain; Richter, Lee J.; Inal, Sahika (ACS Materials Au, American Chemical Society (ACS), 2023-03-06) [Article]
    Organic electrochemical transistors (OECTs) are becoming increasingly ubiquitous in various applications at the interface with biological systems. However, their widespread use is hampered by the scarcity of electron-conducting (n-type) backbones and the poor performance and stability of the existing n-OECTs. Here, we introduce organic salts as a solution additive to improve the transduction capability, shelf life, and operational stability of n-OECTs. We demonstrate that the salt-cast devices present a 10-fold increase in transconductance and achieve at least one year-long stability, while the pristine devices degrade within four months of storage. The salt-added films show improved backbone planarity and greater charge delocalization, leading to higher electronic charge carrier mobility. These films show a distinctly porous morphology where the interconnectivity is affected by the salt type, responsible for OECT speed. The salt-based films display limited changes in morphology and show lower water uptake upon electrochemical doping, a possible reason for the improved device cycling stability. Our work provides a new and easy route to improve n-type OECT performance and stability, which can be adapted for other electrochemical devices with n-type films operating at the aqueous electrolyte interface.
  • Interstitial carbon-platinum electronic metal-support interaction structure boost synergistic removal of O3 and CH3SH via surface atomic oxygen

    Ma, Dingren; Cao, Jing; Liu, Kairui; Zhang, Yexing; Liang, Qiwen; Huang, Yajing; Guan, Xinyi; Hu, Lingling; He, Chun; Xia, Dehua (Applied Catalysis B: Environmental, Elsevier BV, 2023-03-06) [Article]
    Carbon atoms in the interstitial sites of metal nanoparticles have strong influence on heterogeneous catalysis via electronic metal-support interactions (EMSI). Here, the Pt catalysts with interstitial C-Pt EMSI structures were first developed and identified to boost the removal of ozone (O3) and methyl mercaptan (CH3SH). Experimental results showed that the intrinsic activity of the catalysts with low Pt loading (wt%, 0.95 %) was 186 times higher than that of commercial MnO2. This excellent catalytic performance was attributed to dual-site catalytic structures to promote the adsorption/activation of O3 at interstitial C and capture/oxidation of CH3SH at Pt simultaneously. More importantly, the interstitial C sites retained surface atomic oxygen (*O) with excellent reactivity and lowered the energy barrier of C–S bond breakage, thus achieving efficient decomposition of CH3SH into CO2/SO4 2-. This work provides high-performance catalysts and new mechanistic insights for the synergistic control of O3 and CH3SH.
  • A Z-scheme Heterojunctional Photocatalyst Engineered with Spatially Separated Dual Redox Sites for Selective CO2 Reduction with Water: Insight by in-situ μs-transient Absorption Spectra

    Sun, Ling; Zhang, Ziqing; Bian, Ji; Bai, Fuquan; Su, Hengwei; Li, Zhijun; Xie, Jijia; Xu, Rongping; Sun, Jianhui; Bai, Linlu; Chen, Cailing; Han, Yu; Tang, Junwang; Jing, Liqiang (Advanced Materials, Wiley, 2023-03-05) [Article]
    Solar driven CO2 reduction by water with a Z-scheme heterojunction affords an avenue to access energy storage and to alleviate greenhouse gas (GHG) emission, yet the separation of charge carriers and the integrative regulation of water oxidation and CO2 activation sites remain challenging. Here, a BiVO4/g-C3N4 (BVO/CN) Z-scheme heterojunction as such a prototype has been constructed by spatially separated dual sites with CoOx clusters and imidazolium ionic liquids (IL) towards CO2 photoreduction. The optimized CoOx-BVO/CN-IL delivers a ca. 80-fold CO production rate without H2 evolution compared with urea-C3N4 counterpart, together with nearly stoichiometric O2 gas produced. Experimental results and DFT calculations unveil the cascade Z-scheme charge transfer and subsequently the prominent redox co-catalysis by CoOx and IL for holes-H2O oxidation and electrons-CO2 reduction, respectively. Moreover, in-situ μs-transient absorption spectra clearly show the function of each cocatalyst and quantitatively reveal that the resulting CoOx-BVO/CN-IL reaches up to the electron transfer efficiency of 36.4% for CO2 reduction, far beyond those for BVO/CN (4.0%) and urea-CN (0.8%), underlining an exceptional synergy of dual reaction sites engineering. This work provides deep insights and guidelines to the rational design of highly efficient Z-scheme heterojunction with precise redox catalytic sites toward solar fuel production.
  • The dominant component of strong π-hole interactions: electrostatic attraction versus charge transfer.

    Shkurenko, Aleksander (IUCrJ, International Union of Crystallography (IUCr), 2023-03-02) [Article]
  • Supervised Local Training with Backward Links for Deep Neural Networks

    Guo, Wenzhe; Fouda, Mohamed E.; Eltawil, Ahmed; Salama, Khaled N. (IEEE Transactions on Artificial Intelligence, Institute of Electrical and Electronics Engineers (IEEE), 2023-03-02) [Article]
    The restricted training pattern in the standard BP requires end-to-end error propagation, causing large memory costs and prohibiting model parallelization. Existing local training methods aim to resolve the training obstacles by completely cutting off the backward path between modules and isolating their gradients. These methods prevent information exchange between modules and result in inferior performance. This work proposes a novel local training algorithm, BackLink, which introduces inter-module backward dependency and facilitates information to flow backward along with the network. To preserve the computational advantage of local training, BackLink restricts the error propagation length within the module. Extensive experiments performed in various deep convolutional neural networks demonstrate that our method consistently improves the classification performance of local training algorithms over other methods. For example, our method can surpass the conventional greedy local training method by 6.45% in accuracy in ResNet32 classifying CIFAR100 and recent work by 2.58% in ResNet110 classifying STL-10 with much lower complexity, respectively. Analysis of computational costs reveals that small overheads are incurred in GPU memory costs and runtime on multiple GPUs. Our method can lead up to a 79% reduction in memory cost and 52% in simulation runtime in ResNet110 compared to the standard BP. Therefore, our method could create new opportunities for improving training algorithms towards better efficiency for real-time learning applications.
  • Preferential Pyrolysis Construction of Carbon Anodes with 8400 h Lifespan for High-Energy-Density K-ion Batteries.

    Yin, Jian; Jin, Junjie; Chen, Cailing; Lei, Yongjiu; Tian, Zhengnan; Wang, Yizhou; Zhao, Zhiming; Emwas, Abdul-Hamid M.; Zhu, Yunpei; Han, Yu; Schwingenschlögl, Udo; Zhang, Wenli; Alshareef, Husam N. (Angewandte Chemie (International ed. in English), Wiley, 2023-03-01) [Article]
    Carbonaceous materials are promising anodes for practical potassium-ion batteries, but fail to meet the requirements for durability and high capacities at low potentials. Herein, we constructed a durable carbon anode for high-energy-density K-ion full cells by a preferential pyrolysis strategy. Utilizing S and N volatilization from a π-π stacked supermolecule, the preferential pyrolysis process introduces low-potential active sites of sp2 hybridized carbon and carbon vacancies, endowing a low-potential "vacancy-adsorption/intercalation" mechanism. The as-prepared carbon anode exhibits a high capacity of 384.2 mAh g-1 (90% capacity locates below 1 V vs. K/K+), which contributes to a high energy density of 163 Wh kg-1 of K-ion full battery. Moreover, abundant vacancies of carbon alleviate volume variation, boosting the cycling stability over 14,000 cycles (8,400 h). Our work provides a new synthesis approach for durable carbon anodes of K-ion full cells with high energy densities.
  • Process optimization and simulation of biodiesel synthesis from waste cooking oil through supercritical transesterification reaction without catalyst

    Ahmed, Anas; Ali, Abulhassan; Mubashir, Muhammad; Lim, Hooi Ren; Khoo, Kuan Shiong; Show, Pau Loke (JOURNAL OF PHYSICS-ENERGY, IOP Publishing, 2023-02-28) [Article]
    This study reports optimization and simulation of biodiesel synthesis from waste cooking oil through supercritical transesterification reaction without the use of any catalyst. Although the catalyst enhances the reaction rate but due to the presence of water contents in waste cooking oil, the use of catalyst could cause a negative impact on the biodiesel yield. The transesterification reaction without catalyst also offers the advantage of the reduction of pretreatment cost. This study comprises of two steps; first step involves the development and validation of process simulation scheme. The second step involves the optimization using Response Surface Methodology. Face-centered central composite design of experiments is used for experimental matrix development and subsequent statistical analysis of the results. Analysis of variance is employed for optimization purpose. In addition, a sensitivity study of the process parameters including pressure, temperature, and molar ration of oil-to-methanol was conducted. The statistical analysis reveals that temperature is the most influential process parameter as compared to pressure and oil-to-methanol molar ratio. The optimization study results in the maximum biodiesel yield (94.16%) at an optimum temperature of 274.8 °C, 7.02 bar pressure, and an oil-to-methanol molar ratio of 12.43.
  • Data-driven investigation of process solvent and membrane material on organic solvent nanofiltration

    Ignacz, Gergo; Beke, Aron K.; Szekely, Gyorgy (Journal of Membrane Science, Elsevier BV, 2023-02-25) [Article]
    Organic solvent nanofiltration (OSN) studies are largely limited to small and specialized datasets, hindering the investigation of broader relationships and contexts. Larger datasets have recently emerged but they are limited to a single membrane and few solvents. To improve the understanding of solute rejection in OSN, we introduced a large dataset containing 1938 rejection values derived from three membranes and ten industrially relevant green solvents. We examined two polydimethylsiloxane membranes, namely, GMT-oNF-2 and Solsep 030306, and a custom polybenzimidazole membrane. Structure–property relationship methods were used to identify the connections between the performance of membranes, solvents, and solutes. We observed polarity selectivity, which was explained using the classical solution diffusion model, and demonstrated the translation of the rejection database into the corresponding rejection selectivity dataset to characterize separation performance. The obtained rejection selectivity data enabled the process-oriented analysis of solvent and membrane characteristics. Our selectivity-based investigation highlighted the inadequacy of the solute molecular weight to properly characterize membrane material and separation performance. Consequently, our findings support the need for more comprehensive modeling approaches for rejection and process performance prediction, while providing process-oriented insights into the performance of OSN membranes.
  • 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.
  • Adsorption-based capture of iodine and organic iodides: status and challenges

    Pan, Tingting; Yang, Kaijie; Dong, Xinglong; Han, Yu (Journal of Materials Chemistry A, Royal Society of Chemistry (RSC), 2023-02-24) [Article]
    Nuclear energy is a sustainable low-carbon energy source that plays an increasingly important role in supporting the progress of human society. However, there are safety issues associated with the operation of nuclear reactors. In particular, volatile radioactive elements, primarily 129I and 131I, in the form of molecular iodine (I2) or organic iodides (e.g., CH3I and CH3CH2I), are harmful for the environment and human health and must be removed before discharging the off-gas. Adsorption processes employing porous solid adsorbents to capture radioactive iodine compounds have attracted considerable attention owing to their simple operation and low maintenance cost and because they avoid the use of highly corrosive solutions. Despite the efforts devoted to developing novel adsorbents for iodine capture, certain critical issues related to practical applications have been overlooked. This review summarizes the adsorption mechanisms employed to capture I2 and CH3I, focusing on the different adsorbent requirements. This review also compares the static and dynamic evaluation systems, analyzes the structure–function relationship under different testing conditions, and highlights the importance of using appropriate conditions to evaluate adsorbents. Moreover, the simultaneous capture of I2 and CH3I is discussed, which is quite challenging but has been largely ignored in previous studies. Finally, this review outlines the challenges and opportunities in this field from the perspective of materials design and system evaluation, indicating that properly designing adsorbents to provide sufficient chemisorption sites may be the only way to meet the practical application requirements.
  • Interband transition probing of coherent acoustic phonons of gold/metal oxide core–shell nanoparticles

    Wang, Lijie; Oppermann, Malte; Puppin, Michele; Bauer, Benjamin; Chow, Tsz Him; Wang, Jianfang; Chergui, Majed (Applied Physics Letters, AIP Publishing, 2023-02-21) [Article]
    We present ultrafast spectroscopic investigations of the coherent acoustic vibrations of Au/SiO2 and Au/TiO2 core–shell nanoparticles (NPs) upon excitation of the Au surface plasmon resonance. The oscillations are detected in the region of the interband transitions of Au in the deep-ultraviolet, where they appear in the form of intensity modulations with no changes in the spectra. For the Au/SiO2 NPs, the oscillation period (typically ∼10 ps) is similar to that of bare Au NPs having a size identical to that of the core, implying a negligible coupling of the core with the shell. For Au/TiO2 NPs, significantly slower (∼20 ps) oscillations appear, whose period is identical to that of a bare gold NP having the same total diameter, implying that the Au/TiO2 NPs can be treated as a single object. This may due to the strong chemical interaction at the gold/TiO2 interface. Finally, the amplitude modulations are a consequence of the modifications of the band structure of the Au NP, resulting from the strain due to the phonons, which may affect the joint density of states.
  • 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.
  • Atypical stability of exsolved Ni-Fe alloy nanoparticles on double layered perovskite for CO2 dry reforming of methane

    Yao, Xueli; Cheng, Qingpeng; Attada, Yerrayya; Ould-Chikh, Samy; Ramírez, Adrian; Bai, Xueqin; Mohamed, Hend Omar; Li, Guanxing; Shterk, Genrikh; Zheng, Lirong; Gascon, Jorge; Han, Yu; Bakr, Osman; Castaño, Pedro (Applied Catalysis B: Environmental, Elsevier BV, 2023-02-20) [Article]
    Dry reforming of methane simultaneously achieves several sustainability goals: valorizing methane-activating carbon dioxide while producing syngas. The catalyst has an enormous influence on the process viability by controlling activity, selectivity, and stability. A catalyst with uniform-sized Ni-Fe alloy nanoparticles anchored into PrBaMn1.6Ni0.3Fe0.1O5+δ double-layered perovskite is assembled via a facile one-step reduction strategy. Our method attains more exsolved Ni nanoparticles (94 %) than the common conditions. The exsolved Ni0.15Fe0.05 catalyst shows exceptional stability in 260 h tests at 800 °C, with one of the slowest coke formation rates compared with the state-of-the-art catalysts. Besides, no deactivation was observed during 40 h operation at more demanding and coking conditions (14 bar) where this process is more likely to operate industrially. Via experimental characterizations and computational calculations, the stability of the robust exsolved Ni-Fe catalyst is demonstrated by its unique balance of adsorbed species, which inhibits coking.

View more