Search

This work reports the thermal and electron beam stabilities of a series of isostructural metal–organic frameworks (MOFs) of type MFM-300(M) (M = Al, Ga, In, Cr). MFM-300(Cr) was most stable under the electron beam, having an unusually high critical electron fluence of 1111 e− Å−2 while the Group 13 element MOFs were found to be less stable. Within Group 13, MFM-300(Al) had the highest critical electron fluence of 330 e− Å−2, compared to 189 e− Å−2 and 147 e− Å−2 for the Ga and In MOFs, respectively. For all four MOFs, electron beam-induced structural degradation was independent of crystal size and was highly anisotropic, although both the length and width of the channels decreased during electron beam irradiation. Notably, MFM-300(Cr) was found to retain crystallinity while shrinking up to 10%. Thermal stability was studied using in situ synchrotron X-ray diffraction at elevated temperature, which revealed critical temperatures for crystal degradation to be 605, 570, 490 and 480 °C for Al, Cr, Ga, and In, respectively. The pore channel diameters contracted by ≈0.5% on desorption of solvent species, but thermal degradation at higher temperatures was isotropic. The observed electron stabilities were found to scale with the relative inertness of the cations and correlate well to the measured lifetime of the materials when used as photocatalysts. [ABSTRACT FROM AUTHOR]

We report the high NH3 uptake in a series of copper-carboxylate materials, namely MFM-100, MFM-101, MFM-102, MFM-126, MFM-127, MFM-190(F), MFM-170, and Cu-MOP-1a. At 273 K and 1 bar, MFM-101 shows an exceptional uptake of 21.9 mmol g−1. The presence of Cu(II)⋯NH3 interactions and changes in coordination at the [Cu2(O2CR)4] paddlewheel are analysed and discussed. [ABSTRACT FROM AUTHOR]

Formamides are important feedstocks for the manufacture of many fine chemicals. State‐of‐the‐art synthesis of formamides relies on the use of an excess amount of reagents, giving copious waste and thus poor atom‐economy. Here, we report the first example of direct synthesis of N‐formamides by coupling two challenging reactions, namely reductive amination of carbonyl compounds, particularly biomass‐derived aldehydes and ketones, and fixation of CO2 in the presence of H2 over a metal‐organic framework supported ruthenium catalyst, Ru/MFM‐300(Cr). Highly selective production of N‐formamides has been observed for a wide range of carbonyl compounds. Synchrotron X‐ray powder diffraction reveals the presence of strong host‐guest binding interactions via hydrogen bonding and parallel‐displaced π⋅⋅⋅π interactions between the catalyst and adsorbed substrates facilitating the activation of substrates and promoting selectivity to formamides. The use of multifunctional porous catalysts to integrate CO2 utilisation in the synthesis of formamide products will have a significant impact in the sustainable synthesis of feedstock chemicals. [ABSTRACT FROM AUTHOR]

Deuterium labelling of organic compounds is an important process in chemistry. We report the first example of photocatalytic dehalogenative deuteration of both arylhalides and alkylhalides (40 substrates) over a metal–organic framework, MFM‐300(Cr), using CD3CN as the deuterium source at room temperature. MFM‐300(Cr) catalyses high deuterium incorporation and shows excellent tolerance to various functional groups. Synchrotron X‐ray powder diffraction reveals the activation of halogenated substrates via confined binding within MFM‐300(Cr). In situ electron paramagnetic resonance spectroscopy confirms the formation of carbon‐based radicals as intermediates and reveals the reaction pathway. This protocol removes the use of precious‐metal catalysts from state‐of‐the‐art processes based upon direct hydrogen isotope exchange and shows high photocatalytic stability, thus enabling multiple catalytic cycles. [ABSTRACT FROM AUTHOR]

We report the modulation of reactivity of nitrogen dioxide (NO2) in a charged metal–organic framework (MOF) material, MFM‐305‐CH3 in which unbound N‐centres are methylated and the cationic charge counter‐balanced by Cl− ions in the pores. Uptake of NO2 into MFM‐305‐CH3 leads to reaction between NO2 and Cl− to give nitrosyl chloride (NOCl) and NO3− anions. A high dynamic uptake of 6.58 mmol g−1 at 298 K is observed for MFM‐305‐CH3 as measured using a flow of 500 ppm NO2 in He. In contrast, the analogous neutral material, MFM‐305, shows a much lower uptake of 2.38 mmol g−1. The binding domains and reactivity of adsorbed NO2 molecules within MFM‐305‐CH3 and MFM‐305 have been probed using in situ synchrotron X‐ray diffraction, inelastic neutron scattering and by electron paramagnetic resonance, high‐field solid‐state nuclear magnetic resonance and UV/Vis spectroscopies. The design of charged porous sorbents provides a new platform to control the reactivity of corrosive air pollutants. [ABSTRACT FROM AUTHOR]

The interactions between adsorbed gas molecules within porous metal-organic frameworks are crucial to gas selectivity but remain poorly explored. Here, we report the modulation of packing geometries of CO2 and C2H2 clusters within the ultramicroporous CUK-1 material as a function of temperature. In-situ synchrotron X-ray diffraction reveals a unique temperature-dependent reversal of CO2 and C2H2 adsorption affinities on CUK-1, which is validated by gas sorption and dynamic breakthrough experiments, affording high-purity C2H2 (99.95%) from the equimolar mixture of C2H2/CO2 via a one-step purification process. At low temperatures (<253 K), CUK-1 preferentially adsorbs CO2 with both high selectivity (>10) and capacity (170 cm3 g−1) owing to the formation of CO2 tetramers that simultaneously maximize the guest-guest and host-guest interactions. At room temperature, conventionally selective adsorption of C2H2 is observed. The selectivity reversal, structural robustness, and facile regeneration of CUK-1 suggest its potential for producing high-purity C2H2 by temperature-swing sorption. Guest clusters within confined nanospaces have a significant impact on molecular recognition. Here authors highlight the potential to systematically control gas-cluster rearrangement, leading to tunable sorption and separation behaviour in a MOF. [ABSTRACT FROM AUTHOR]

The development of cost‐effective sorbents for direct capture of trace CO2 (<1 %) from the atmosphere is an important and challenging task. Natural or commercial zeolites are promising sorbents, but their performance in adsorption of trace CO2 has been poorly explored to date. A systematic study on capture of trace CO2 by commercial faujasite zeolites reveals that the extra‐framework cations play a key role on their performance. Under dry conditions, Ba−X displays high dynamic uptake of 1.79 and 0.69 mmol g−1 at CO2 concentrations of 10000 and 1000 ppm, respectively, and shows excellent recyclability in the temperature‐swing adsorption processes. K−X exhibits perfect moisture resistance, and >95 % dry CO2 uptake can be preserved under relative humidity of 74 %. In situ solid‐state NMR spectroscopy, synchrotron X‐ray diffraction and neutron diffraction reveal two binding sites for CO2 in these zeolites, namely the basic framework oxygen atoms and the divalent alkaline earth metal ions. This study unlocks the potential of low‐cost natural zeolites for applications in direct air capture. [ABSTRACT FROM AUTHOR]

We report reversible high capacity adsorption of SO2 in robust Zr‐based metal–organic framework (MOF) materials. Zr‐bptc (H4bptc=biphenyl‐3,3′,5,5′‐tetracarboxylic acid) shows a high SO2 uptake of 6.2 mmol g−1 at 0.1 bar and 298 K, reflecting excellent capture capability and removal of SO2 at low concentration (2500 ppm). Dynamic breakthrough experiments confirm that the introduction of amine, atomically‐dispersed CuII or heteroatomic sulphur sites into the pores enhance the capture of SO2 at low concentrations. The captured SO2 can be converted quantitatively to a pharmaceutical intermediate, aryl N‐aminosulfonamide, thus converting waste to chemical values. In situ X‐ray diffraction, infrared micro‐spectroscopy and inelastic neutron scattering enable the visualisation of the binding domains of adsorbed SO2 molecules and host–guest binding dynamics in these materials at the atomic level. Refinement of the pore environment plays a critical role in designing efficient sorbent materials. [ABSTRACT FROM AUTHOR]

Background: Early screening and treatment of esophageal cancer (EC) is particularly important for the survival and prognosis of patients. However, early EC is difficult to diagnose by a routine endoscopic examination. Therefore, convolutional neural network (CNN)-based artificial intelligence (AI) has become a very promising method in the diagnosis of early EC using endoscopic images. The aim of this study was to evaluate the diagnostic performance of CNN-based AI for detecting early EC based on endoscopic images. Methods: A comprehensive search was performed to identify relevant English articles concerning CNN-based AI in the diagnosis of early EC based on endoscopic images (from the date of database establishment to April 2022). The pooled sensitivity (SEN), pooled specificity (SPE), positive likelihood ratio (LR+), negative likelihood ratio (LR−), diagnostic odds ratio (DOR) with 95% confidence interval (CI), summary receiver operating characteristic (SROC) curve, and area under the curve (AUC) for the accuracy of CNN-based AI in the diagnosis of early EC based on endoscopic images were calculated. We used the I2 test to assess heterogeneity and investigated the source of heterogeneity by performing meta-regression analysis. Publication bias was assessed using Deeks' funnel plot asymmetry test. Results: Seven studies met the eligibility criteria. The SEN and SPE were 0.90 (95% confidence interval [CI]: 0.82–0.94) and 0.91 (95% CI: 0.79–0.96), respectively. The LR+ of the malignant ultrasonic features was 9.8 (95% CI: 3.8–24.8) and the LR− was 0.11 (95% CI: 0.06–0.21), revealing that CNN-based AI exhibited an excellent ability to confirm or exclude early EC on endoscopic images. Additionally, SROC curves showed that the AUC of the CNN-based AI in the diagnosis of early EC based on endoscopic images was 0.95 (95% CI: 0.93–0.97), demonstrating that CNN-based AI has good diagnostic value for early EC based on endoscopic images. Conclusions: Based on our meta-analysis, CNN-based AI is an excellent diagnostic tool with high sensitivity, specificity, and AUC in the diagnosis of early EC based on endoscopic images. [ABSTRACT FROM AUTHOR]

Air pollution by SO2 and NO2 has caused significant risks on the environment and human health. Understanding the mechanism of active sites within capture materials is of fundamental importance to the development of new clean‐up technologies. Here we report the crystallographic observation of reversible coordinative binding of SO2 and NO2 on open NiII sites in a metal‐organic framework (NKU‐100) incorporating unprecedented {Ni12}‐wheels; each wheel exhibits six open NiII sites on desolvation. Immobilised gas molecules are further stabilised by cooperative host‐guest interactions comprised of hydrogen bonds, π⋅⋅⋅π interactions and dipole interactions. At 298 K and 1.0 bar, NKU‐100 shows adsorption uptakes of 6.21 and 5.80 mmol g−1 for SO2 and NO2, respectively. Dynamic breakthrough experiments have confirmed the selective retention of SO2 and NO2 at low concentrations under dry conditions. This work will inspire the future design of efficient sorbents for the capture of SO2 and NO2. [ABSTRACT FROM AUTHOR]

Industrial purification of propylene and ethylene requires cryogenic distillation and selective hydrogenation over palladium catalysts to remove propane, ethane and/or trace amounts of acetylene. Here, we report the excellent separation of equimolar mixtures of propylene/propane and ethylene/ethane, and of a 1/100 mixture of acetylene/ethylene by a highly robust microporous material, MFM‐520, under dynamic conditions. In situ synchrotron single crystal X‐ray diffraction, inelastic neutron scattering and analysis of adsorption thermodynamic parameters reveal that a series of synergistic host–guest interactions involving hydrogen bonding and π⋅⋅⋅π stacking interactions underpin the cooperative binding of alkenes within the pore. Notably, the optimal pore geometry of the material enables selective accommodation of acetylene. The practical potential of this porous material has been demonstrated by fabricating mixed‐matrix membranes comprising MFM‐520, Matrimid and PIM‐1, and these exhibit not only a high permeability for propylene (≈1984 Barrer), but also a separation factor of 7.8 for an equimolar mixture of propylene/propane at 298 K. [ABSTRACT FROM AUTHOR]

The metallo-formate anions, M(CO2)−, M = Ni, Pd, and Pt, were formed by electron-induced CO2 activation. They were generated by laser vaporization and characterized by a combination of mass spectrometry, anion photoelectron spectroscopy, and theoretical calculations. While neutral transition metal atoms are normally unable to activate CO2, the addition of an excess electron to these systems led to the formation of chemisorbed anionic complexes. These are covalently bound, formate-like anions, in which their CO2 moieties are significantly reduced. In addition, we also found evidence for an unexpectedly attractive interaction between neutral Pd atoms and CO2. [ABSTRACT FROM AUTHOR]

The solution‐processed 8‐hydroquinolatolithium (Liq) has first been demonstrated as a highly effective cathode interfacial layer (CIL) in inverted perovskite solar cells (PSCs). Compared with the control device without a CIL, the Liq‐based device possesses a faster charge transport rate, a lower surface work function of Ag electrode, a larger built‐in potential, and a higher charge recombination resistance, probably due to the formed interface dipole between [6,6]‐phenyl‐C61‐butyric acid methyl ester (PCBM) and Ag induced by Liq, which eventually results in a great improvement of device performance. After optimization, the Liq‐based PSC has achieved a power conversion efficiency higher than 19%. These results will assuredly expand the present limited range of available solution‐processable cathode interfacial materials for low‐cost high‐performance PSCs. [ABSTRACT FROM AUTHOR]

The International Archive of Women in Architecture, established at Virginia Tech in 1985, collects books, biographical information, and published materials from nearly 40 countries that are divided into around 450 collections. In order to provide public access to these collections, we built an application using the IIIF APIs to pre-generate image tiles and manifests which are statically served in the AWS cloud. We established an automatic image processing pipeline using a suite of AWS services to implement microservices in Lambda and Docker. By doing so, we reduced the processing time for terabytes of images from weeks to days. In this article, we describe our serverless architecture design and implementations, elaborate the technical solution on integrating multiple AWS services with other techniques into the application, and describe our streamlined and scalable approach to handle extremely large image datasets. Finally, we show the significantly improved performance compared to traditional processing architectures along with a cost evaluation. [ABSTRACT FROM AUTHOR]