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The crystallographic pore sizes of zeolites are substantially smaller than those inferred from catalytic transformation and molecular sieving capabilities, which reflects flexible variation in zeolite opening pores. Using in situ electron microscopy, we imaged the straight channels of ZSM-5 zeolite with benzene as a probe molecule and observed subcell flexibility of the framework. The opening pores stretched along the longest direction of confined benzene molecules with a maximum aspect change of 15%, and thePnmaspace group symmetry of the MFI framework caused adjacent channels to deform. This compensation maintained the stability and rigidity of the overall unit cell within 0.5% deformation. The subcell flexibility originates mainly from the topologically soft silicon-oxygen-silicon hinges between rigid tetrahedral SiO4units, with inner angles varying from 135° to 153°, as confirmed by ab initio molecular dynamics simulations.

Surface and interface, with unique local characteristics different from bulk structure, are of great significance in various applications of metal-organic frameworks (MOFs), which should be studied by real-space imaging methods, such as electron microscopy. However, it is still challenging to atomically resolve these local structures in MOFs, because they are even more sensitive to electron irradiation. Here, we use integrated differential phase contrast scanning transmission electron microscopy (iDPC-STEM) to achieve the atomic imaging of both the metal nodes and organic linkers in UiO-66 (Zr) nanocrystals and their assembly. After adding acetic acid, we modulate the whole process of MOF assembly and observe the organic linkers at both the surfaces and twin interfaces in the chemically assembled UiO-66 (Zr) crystals by the iDPC-STEM. These results bring us a deeper understanding on the role of acid modulators that promote the MOF assembly by generating the missing-linker defects on the crystal surface.

Single-molecule imaging is challenging but highly beneficial for investigating intermolecular interactions at the molecular level1–6. Van der Waals interactions at the sub-nanometre scale strongly influence various molecular behaviours under confinement conditions7–11. Inspired by the traditional compass12, here we use a para-xylene molecule as a rotating pointer to detect the host–guest van der Waals interactions in the straight channel of the MFI-type zeolite framework. We use integrated differential phase contrast scanning transmission electron microscopy13–15 to achieve real-space imaging of a single para-xylene molecule in each channel. A good correlation between the orientation of the single-molecule pointer and the atomic structure of the channel is established by combining the results of calculations and imaging studies. The orientations of para-xylene help us to identify changes in the van der Waals interactions, which are related to the channel geometry in both spatial and temporal dimensions. This work not only provides a visible and sensitive means to investigate host–guest van der Waals interactions in porous materials at the molecular level, but also encourages the further study of other single-molecule behaviours using electron microscopy techniques. The orientation of a rotating para-xylene molecule in the nanochannel of a zeolite framework can be visualised by electron microscopy to determine the host–guest van der Waals interaction inside the channel.

The micro-structures of catalyst materials basically affect their macro-architectures and catalytic performances. Atomically resolving the micro-structures of zeolite catalysts, which have been widely used in the methanol conversion, will bring us a deeper insight into their structure-property correlations. However, it is still challenging for the atomic imaging of silicoaluminophosphate zeolites by electron microscopy due to the limits of their electron beam sensitivity. Here, we achieve the real-space imaging of the atomic lattices in SAPO-34 and SAPO-18 zeolites, including the Al–O–P atoms and bonds, by the integrated differential phase contrast scanning transmission electron microscopy (iDPC-STEM). The spatial distribution of SAPO-34 and SAPO-18 domains in SAPO-34/18 intergrowths can be clearly resolved. By changing the Si contents and templates in feed, we obtain two SAPO-34/18 catalysts, hierarchical and sandwich catalysts, with highly-mixed and separated SAPO-34 and SAPO-18 lattices respectively. The reduced diffusion distances of inside products greatly improve the catalytic performances of two catalysts in methanol conversion. Based on the observed distributions of lattices and elements in these catalysts, we can have a preliminary understanding on the correlation between the synthesis conditions and structures of SAPO-34/18 intergrowth catalysts to further modify their performances based on unique architectures., The micro-structures of zeolite catalysts affect their macroarchitectures and catalytic performances. Here, the different SAPO-34/18 intergrowth catalysts are atomically resolved, and the correlation between synthesis conditions and zeolite structures is revealed to further enhance their performances in methanol conversion.

We report the effect of water on the conversion of ethene with H-ZSM-5 to make aromatics at 300–500 °C. We found that water seriously decreased the conversion of ethene and the yield of aromatics, ...

A temperature-shifting two-stage fluidized bed reactor technology was used to convert propane and its intermediate products into aromatics. The first stage served for the aromatization of propane with a Ga/ZSM-5 catalyst at 570 °C. The second stage served for the alkylation of the intermediates of olefins at 300 °C. The increased yield of aromatics was attributed to the effective transformation of C2–C3 olefins as well as due to the suppression of the hydrogen transfer effect of the olefins.

Single-molecule imaging with atomic resolution is a notable method to study various molecular behaviours and interactions

Imaging the single molecules is always challenging under the diverse microscopes, but highly demanded for investigating the intermolecular interactions at the molecular level1-6. The van der Waals (vdW) interactions at sub-nanometer scale will deeply influence various molecular behaviors under the confinement conditions7-11. Here, inspired by the traditional compass12, we introduce a classical strategy using a vertical para-xylene (PX) molecule as a rotating pointer to detect the vdW potential field in a MFI straight channel. Based on the integrated differential phase contrast scanning transmission electron microscopy (iDPC-STEM)13-17, we achieve the real-space imaging of single PX molecule pointer in each channel with a certain orientation. The solid relation between the pointer orientation and atomic channel structure in this vdW compass is established by combining the calculations and imaging results. Thus, these PX orientations help us identify the varied vdW potential field related to the channel geometry both in the spatial and temporal dimensions. This work not only provides a visible and sensitive pointer to investigate the host-guest vdW interactions in porous materials at the molecular level, but also promotes the further imaging and study of other single-molecule behaviors by the iDPC-STEM.

Background Working memory deficit is one of the most critical complex cognitive impairments in schizophrenia. Repetitive transcranial magnetic stimulation (rTMS) is an effective adjuvant therapy, but not still unsatisfactory. Intermittent theta burst stimulation (iTBS), which has recently been used in clinical practice, may have faster and stronger effects comparing the traditional model (10-Hz high-frequency rTMS). A large number of studies have showed that rTMS, especially iTBS, can enhance the neural plasticity of the brain, and cognitive training can improve the cognitive function of schizophrenia. Is there any facilitation effect of iTBS add on cognitive training (such as working memory training, WMT) on cognitive function enhancement in schizophrenia is still unknown. Methods/design The proposed study is designed of a double-center, double-blinded, randomized controlled trial that will include 200 schizophrenia patients between 18 and 45 years of age. The patients will be randomized to four groups, i.e., the study group (iTBS+WMT), WMS control group (iTBS+ Simple Response Training (SRT)), iTBS control group (sham iTBS+WMT), and placebo control (sham iTBS+SRT). The patients will receive 3 min 20 s of real or sham stimulation, followed by a short 1–2-min rest and 40 min of WMT training or SRT immediately. Neuropsychological and clinical symptom assessments, with functional and structural MRI, will be performed on baseline, post-treatment, and 3- and 6-month follow-up periods. The primary outcome is cognitive function measured by the MATRICS Consensus Cognitive Battery (MCCB). The secondary outcomes are changes in neuroplasticity, as measured by MRI and other behavioral assessments. Discussion The aim of our study is to explore the facilitation effects of iTBS added on WMT in improving cognitive function of schizophrenia. That means, patients with schizophrenia will benefit more in cognitive function improvement from the combination training mode of “preheating (iTBS stimulation changes the neural activity of working memory-related brain regions) and ironning (working memory training).” And the long-term effects of this combined training model will be assessed at a 6-month follow-up period. In case of a significant improvement of working memory with a prolonged effect, the iTBS combined with WMT protocol could be considered as a first-line clinical protocol in schizophrenia treatment. More broadly, the potential for increased universality and efficiency of rTMS with the iTBS model to enhance the neural plasticity of the brain should have a more positive effect on cognitive function in schizophrenia. Trial registration chictr.org.cn ChiCTR1900023405. Registered on 25 May 2019

Additional file 1. SPIRIT 2013 Checklist: Recommended items to address in a clinical trial protocol and related documents.

A hierarchical microporous graphitic carbon material intrinsically doped with sulfur and extrinsically doped with dual cobalt species [Co3O4 and Co(PO3)2, termed as CoOP] nanoparticles was prepared from a sustainable waste biomass, peanut shell, with CO2 gas as the activating agent through a thermal-reduction method. The resulting CoOP@bio-C exhibits an overall superior ORR catalytic activity, stability and resistance to methanol crossover in alkaline media to commercial Pt/C, with onset and half-wave potentials of 0.91 and 0.81 V in 0.1 M KOH, a limiting current density of −5.7 mA cm−2, and a small Tafel slope of 57 mV dec−1, representing the best result among the biomass-based carbon electrocatalysts. In particular, comparative studies reveal the significant effect of the work function of corresponding catalytic materials on the ORR electrocatalysis. Dual-doped CoOP@bio-C with a work function of 5.42 eV, closer to that of Pt (5.65 eV), displays much better electrocatalytic activity than single-doped Co3O4@bio-C, single-doped Co(PO3)2@bio-C and bio-C-800 catalysts with work functions of 8.35, 6.61 and 5.02 eV, respectively, due to its good adsorption nature to O2 and desorption nature to the reaction intermediates. The present result will be surely helpful for the design and synthesis of biomass resource-based ORR catalysts with great application potential.

To investigate the effect of fluorine–hydrogen bonding and metal–ligand coordination on the morphology and gas sensing properties of self-assembled nanostructures, metal free 2,3,9,10,16,17,24,25-octakis(heptafluorobutoxy)phthalocyanine H2[Pc(OCH2C3F7)8] (1) and its zinc complex counterpart Zn[Pc(OCH2C3F7)8] (2) are synthesized and fabricated into organic microstructures by a phase-transfer method. The self-assembling properties have been comparatively investigated by electronic absorption and Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), X-ray diffraction (XRD) and current–voltage (I–V) measurements. Competition and cooperation between the inter-molecular π-π interaction and C-H⋯F-C hydrogen bonding in the direction perpendicular to the π-π interaction direction for metal-free phthalocyanine 1 lead to the formation of uniformed two-dimensional helical microribbons with an aspect ratio (length/width) of ca 20. The additional Zn-O coordination interactions between the central zinc ion and the oxygen atom of the adjacent molecule increases the intermolecular interaction, and results in the formation of long one-dimensional nanowires for 2 with an aspect ratio of more than 200. Notably, the resulting microstructures were revealed to show good semiconducting properties with the increasing conductivity from 5.99 × 10−5 S cm−1 for the nanowires of 2 to 1.68 × 10−4 S cm−1 for the helical ribbons of 1. Moreover, the excellently sensitive, stable and reproducible responses to NO2 in 50–900 ppb range are observed for the helical ribbons of 1 at room temperature, implying the excellent potential as the NO2 sensor for applications in practical environments. Both sensitivity and detection limit of the helical ribbons of 1 for NO2 gas at room temperature was found to be better than those of the nanowires of 2. This suggests that the analyte-phthalocyanine interaction is dominated by not only high conductivity and great surface area but more importantly binding strength of analyte to the central cavity of the phthalocyanine.

Single-molecule imaging is challenging but highly beneficial for investigating intermolecular interactions at the molecular level

Methanol to aromatics (MTA) process not only involves the dehydrogenation-aromatization reactions but also the undesirable side reactions (e.g., hydrogen transfer, dealkylation, disproportionation, isomerization). As-produced aromatics composition was not favorable for the subsequent para-xylene (PX) manufacturing process in the MTA plant. In this study, we proposed the decentralized methonal feed strategy for process intensification of MTA and compared the effects of the centralized feed and decentralized feed on MTA reaction. It was found that the decentralized feed could weaken the occurrence of side reactions and affect the product distribution, the aromatics yield produced no change though. By inhibiting the dealkylation and disproportionation and isomerization reactions, the decentralized feed decreased the yields of benzene (B) and toluene (T) while increased the xylene (X) yield and PX selectivity in X beyond thermodynamic equilibrium, which is highly expected in industry. With the decentralized feed, the restricted hydrogen transfer reaction increased olefins and C5+ non-aromatics, which could be further converted into aromatics, and reduced unwanted alkanes. Our methodology of process intensification provided insight into product distribution optimization to match large materials flow in terms of PX production in the MTA plant.

Methanol to aromatics (MTA) following dual cycles concept unavoidably produced considerable amounts of olefinic intermediates and paraffinic by-products. Their formation and further conversion were vital to improving aromatics production. In this study, a two-stage fluid bed packed with fluid Zn/ZSM-5 catalyst in each stage was used to investigate the MTA reaction at 470 °C in the first stage and the secondary conversion of MTA primary products at temperatures from 270 °C to 550 °C in the second stage with time on stream. During the MTA reaction, the decrease of catalyst acidity was beneficial to controlling hydrogen transfer, thus blocking propane formation. During the secondary conversion of MTA products, at temperatures below 390 °C, the alkylation and hydrogen transfer reactions dominated and thus olefins were converted into more alkylbenzene as well as the undesired propane and butane. As the temperature increased from 430 °C to 550 °C, the aromatization of light hydrocarbon and the dealkylation of alkylbenzene were facilitated, producing more benzene and toluene but increasing methane and ethane yields. Meanwhile, the dehydrogenation and cracking of propane and butane were favored by high temperature and strong acidity so that the yields of ethene and propene increased. It was clarified that the characteristics of secondary conversion of MTA products varied and depended on reaction temperature and catalyst acidity. Based on these findings, the concept of regional functionalization of fluidized bed reactor was proposed for intensification of MTA process based on the reconfiguration of the temperature and acidity of catalyst stream during the fluidized bed reaction-regeneration cycle.