Synergy of pore size and silanols in an -SVR-type zeolite for efficient dynamic benzene/cyclohexane separation.

The efficient purification of cyclohexane is critical, serving as an essential feedstock to produce resins, nylon fibers and pharmaceutical intermediates. However, efficient purification remains a challenging task due to the similarity of cyclohexane and benzene molecules in terms of size and boiling point. In this work, we reported on the synergy of pore size and silanols inside an -SVR-type zeolite for the efficient production of ultrapure cyclohexane (benzene <1 ppm) from benzene/cyclohexane mixture. Under ambient conditions, the SSZ-74 zeolite demonstrated the highest mass-based productivity of 14.5 L/kg for ultrapure cyclohexane among several common zeolites with a considerable dynamic selectivity of ~9.5. The separation ability was evaluated through density functional theory (DFT) calculations and ab initio molecular dynamics (AIMD) simulations. The unique ordered silanols inside the zeolite frameworks demonstrated strong but reversible interactions with benzene through SiOH…π interactions, as revealed by in situ Fourier Transform infrared (FTIR) spectra.

Confinement-Driven Dimethyl Ether Carbonylation in Mordenite Zeolite as an Ultramicroscopic Reactor.

ConspectusThe conversion of C1 molecules to methyl acetate through the carbonylation of dimethyl ether in mordenite zeolite is an appealing reaction and a crucial step in the industrial coal-to-ethanol process. Mordenite zeolite has large 12-membered-ring (12MR) channels (7.0 × 6.5 Å2) and small 8MR channels (5.7 × 2.6 Å2) connected by a side pocket (4.8 × 3.4 Å2), and this unique pore architecture supplies its high catalytic activity to the key step of carbonylation. However, the reaction mechanism of carbonylation in mordenite zeolite is not thoroughly established in that it is able to explain all experimental phenomena and improve its industrial applications, and the classical potential energy surface exerted by static density function theory calculations cannot reflect the reaction kinetics under realistic conditions because the diffusion kinetics of bulk DME (kinetic dimeter: 4.5 Å) and methyl acetate (MA, kinetic dimeter: 5.5 Å) were not well considered and their restricted diffusion in the narrow side pocket and 8MR channels may greatly alter the integrated kinetics of DME carbonylation in mordenite zeolite. Moreover, the precise illustration of the dynamic behaviors of the ketene intermediate and its derivatives (surface acetate and acylium ion) confined within various voids in mordenite has not been effectively portrayed.Advanced ab initio molecular dynamics (AIMD) simulations with or without the acceleration of enhanced sampling methods provide tremendous opportunities for operando modeling of both reaction and diffusion processes and further identify the geometrical structure and chemical properties of the reactants, intermediates, and products in the different confined voids of mordenite under realistic reaction conditions, which enables high consistency between computations and experiments.In this Account, the carbonylation process in mordenite is comprehensively described by the results of decades of continuous research and newly acquired knowledge from both multiscale simulations and in-(ex-)situ spectroscopic experiments. Three primary steps (DME demethylation to surface methoxy species (SMS), carbon-carbon bond coupling between SMS and CO to acetyl species, and methyl acetate formation by acetyl species and methanol/DME) have been respectively studied with a careful consideration of different molecular factors (reactant distribution, concentration, and attack mode). By utilizing the free-energy surface of diffusion and reaction obtained from AIMD simulations, a comprehensive reaction/diffusion kinetic model was formulated for the first time, illustrating the entire zeolite catalytic process. In this context, a comprehensive and informative analysis of the reaction kinetics of carbonylation in mordenite, including the function of the 12MR channels, 8MR channels, and side pockets in the adsorption, diffusion, and reaction of DME carbonylation, was performed. The different channels of mordenite play different roles in all ordered reaction steps, illustrating a highly organized ultramicroscopic reactor that is encompassed.

Facet-dependent diversity of Pt-O coordination for Pt 1 /CeO 2 catalysts achieved by oriented atomic deposition.

The surface chemistry of CeO2 is dictated by the well-defined facets, which exert great influence on the supported metal species and the catalytic performance. Here we report Pt1/CeO2 catalysts exhibiting specific structures of Pt-O coordination on different facets by using adequate preparation methods. The simple impregnation method results in Pt-O3 coordination on the predominantly exposed {111} facets, while the photo-deposition method achieves oriented atomic deposition for Pt-O4 coordination into the "nano-pocket" structure of {100} facets at the top. Compared to the impregnated Pt1/CeO2 catalyst showing normal redox properties and low-temperature activity for CO oxidation, the photo-deposited Pt1/CeO2 exhibits uncustomary strong metal-support interaction and extraordinary high-temperature stability. The preparation methods dictate the facet-dependent diversity of Pt-O coordination, resulting in the further activity-selectivity trade-off. By applying specific preparation routes, our work provides an example of disentangling the effects of support facets and coordination environments for nano-catalysts.

Seed size and dispersal mode select mast seeding in perennial plants.

Reproduction by perennial plants varies from being relatively constant over years to the production of massive and synchronous seed crops at irregular intervals, a reproductive strategy called mast seeding. The sources of interspecific differences in the extent of interannual variation in seed production are largely unknown. We conducted a global meta-analysis of animal-dispersed species to quantify how the interannual variability in seed crops produced by plants can be explained by the seed mass, dispersal mode, phylogeny, and climate. Phylogenetic analysis indicated that the interannual variations in seed production and seed mass tended to be similar in related species due to their shared evolution. The interannual variation in seed production was 1.22 times higher in synzoochorous species dispersed by scatter-hoarders compared with endozoochorous species dispersed by frugivores. Furthermore, the production of small seeds was associated with higher interannual variation in seed production, although synzoochorous species produced larger seeds than endozoochorous species. Precipitation rather than temperature had a significant positive effect on the interannual variation in seed production. The seed mass and dispersal mode contributed more to the interannual variation in seed production than phylogeny, climate, and fruit type. Our findings support a long-standing hypothesis that interspecific variation in the masting intensity is largely shaped by interactions between plants and animals.

High-tannin food enhances spatial memory and scatter-hoarding in rodents via the microbiota-gut-brain axis.

BACKGROUND: The mutually beneficial coevolutionary relationships between rodents and plant seeds have been a theme of research in plant-animal relationships. Seed tannins are important secondary metabolites of plants that regulate the food-hoarding behavior of rodents; however, the underlying molecular mechanisms are not yet clear. In this study, we investigated whether and how seed tannins improve spatial memory and regulate the hoarding behavior of Tamias sibiricus by altering their gut microbiota. RESULTS: We showed that acorn tannins not only improved spatial memory but also enhanced scatter-hoarding in T. sibiricus. Changes in the composition and function of the gut microbiota in response to tannins from acorns are closely related to these improvements. Metabonomic analyses revealed the role of gut isovaleric acid and isobutyric acid as well as serum L-tryptophan in mediating the spatial memory of T. sibiricus via the gut microbiota. The hippocampal proteome provides further evidence that the microbiota-gut-brain axis regulates spatial memory and scatter-hoarding in animals. Our study is likely the first to report that plant secondary metabolites improve hippocampal function and spatial memory and ultimately modulate food-hoarding behavior via the microbiota-gut-brain axis. CONCLUSION: Our findings may have resolved the long-standing puzzle about the hidden role of plant secondary metabolites in manipulating food-hoarding behavior in rodents via the microbiota-gut-brain axis. Our study is important for better understanding the mutualistic coevolution between plants and animals. Video Abstract.

Substrate scent-induced disproportionate seed dispersal by rodents.

Conspecific adults impose strong negative density-dependent effects on seed survival nearby parent trees, however, the underlying mechanisms are diversified and remain unclear. In this study, we presented consistent evidence that parent-scented forest floor masked seed odor, reduced cache recovery rate by scatter-hoarding animals, and then increased seed dispersal far away from mother trees. Our results showed that seed odors of Korean pine Pinus koraiensis match well with the volatile profile of their forest floor. Moreover, scatter-hoarding animals selectively transported P. koraiensis seeds toward the areas where seed odor was more contrasting against the background substrate, possibly due to the fact that accumulation of conspecific volatile compounds in caches hindered seed detection by scatter-hoarding animals. Our study provides insight into the role of leaf litter in directing seed dispersal process, representing a novel mechanism by which P. koraiensis increases selection for seed dispersal far away from the parent tree.

Mast seeding is stronger in taller plants.

Introduction: Two economies of scale, predator satiation and pollination efficiency, have been proposed to explain the evolutionary mechanisms of mast seeding adopted by some long-lived plants. Plant height is strongly selected by pollination vectors and may also provide economies of scale; however, it remains unknown whether there is a close relationship between adult plant height and mast seeding intensity. Methods: Here, we analyzed mast seeding intensity of 158 plant species to test if adult plant height can select for mast seeding. Results: We show that mast seeding intensities are higher in taller plant species irrespective of phylogeny, life form, pollination vector, and type of Spermatophytes. We also show that anemophily rather than entomophily selects for taller plant species and higher mast seeding intensities. Discussion: The linear correlations and evolutionary links between adult plant height and mast seeding intensity provide evidence that mast seeding could have evolved as an adaptation to taller strategy of perennial plant species.

Comparative transcriptome analyses reveal regulatory network and hub genes of aluminum response in roots of elephant grass (Cenchrus purpureus).

Aluminum (Al) toxicity severely restricts the growth and productivity of elephant grass in acidic soils around the world. However, the molecular mechanisms of Al response have not been investigated in elephant grass. In this study, we conducted phenotype, physiology, and transcriptome analysis of elephant grass roots in response to Al stress. Phenotypic analysis revealed that a low concentration of Al stress improved root growth while higher Al concentrations inhibit root growth. Al stress significantly increased the citrate (CA) content in roots, while the expression levels of genes related to citrate synthesis were substantially changed. The multidrug and toxic compound extrusion (MATE) family were identified as hub genes in the co-expression network of Al response in elephant grass roots. Phylogenetic analysis showed that hub genes CpMATE93 and CpMATE158 belonged to the same clade as other MATE genes reported to be involved in citrate transport. Additionally, overexpression of CpMATE93 conferred Al resistance in yeast cells. These results provide a theoretical basis for further studies of molecular mechanisms in the elephant grass response to Al stress and could help breeders develop elite cultivars with Al tolerance.

Masting promotes transformation from predation to mutualism in an oak-weevil-rodent system.

The significance of ecological non-monotonicity (a function whose first derivative changes signs) in shaping the structure and functions of the ecosystem has recently been recognized, but such studies involving high-order interactions are rare. Here, we have proposed a three-trophic conceptual diagram on interactions among trees, rodents, and insects in mast and non-mast years and tested the hypothesis that oak (Quercus wutaishanica) masting could result in increased mutualism and less predation in an oak-weevil-rodent system in a warm temperate forest of China. Our 14-year dataset revealed that mast years coincided with a relatively low rodent abundance but a high weevil abundance. Masting not only benefited seedling recruitment of oaks through increased dispersal by rodents but also a decrease in predation by rodents and weevils, as well as an increase in the overwintering survival of rodents. Masting appeared to have increased weevil survival by reducing predation of infested acorns by rodents. These results suggest that masting benefits all participants in the plant-insect-rodent system by increasing mutualism and reducing predation behavior (i.e., a non-monotonic function). Our study highlights the significance of masting in maintaining the diversity and function of the forest ecosystem by facilitating the transformation from predation to mutualism among trophic species.

Novel host plant use by a specialist insect depends on geographic variation in both the host and herbivore species.

Understanding the circumstances under which insect herbivores will adopt a novel host plant is a longstanding question in basic and applied ecology. While geographic variation in host use can arise through differences in both herbivore preference and plant characteristics, there is a tendency to attribute geographic variation in host use to regional differences in herbivore preference alone. This is especially true for herbivores specialized to one or a few plant species. We compared how geographic variation in herbivore preference and host plant origin shape regional differences in host plant use by the specialized herbivore, Euphydryas phaeton. In parts of its range, E. phaeton uses only a native host, Chelone glabra, while in others, it also uses an introduced host, Plantago lanceolata. We offered female butterflies from each region the non-native host plant sourced from both regions and compared their oviposition behavior. The non-native host was almost universally rejected by butterflies in the region where only the native plant is used. In the region where butterflies use both hosts, females accepted non-native plants from their natal region twice as often as non-native plants from the other region where they are not used. Acceptance differed substantially among individual butterflies within regions but not among plants within regions. Thus, both individual preference and regional differences in both the insect and non-native host contributed to the geographic variation in different ways. These results highlight that, in addition to herbivore preference, regional differences in perceived plant suitability may be an important driver of diet breadth.

Spectroscopically Visualizing the Evolution of Hydrogen-Bonding Interactions.

Understanding chemical bond variations is the soul of chemistry as it is essential for any chemical process. The evolution of hydrogen bonds is one of the most fundamental and emblematic events during proton transfer; however, its experimental visualization remains a formidable challenge because of the transient timescales. Herein, by subtly regulating the proton-donating ability of distinct proton donors (zeolites or tungstophosphoric acid), a series of different hydrogen-bonding configurations were precisely manipulated. Then, an advanced two-dimensional (2D) heteronuclear correlation nuclear magnetic resonance (NMR) spectroscopic technique was utilized to simultaneously monitor the electronic properties of proton donors and acceptors (2-13C-acetone or trimethylphosphine oxide) through chemical shifts. Parabolic 1H-13C NMR relationships combined with single-well and double-well potential energy surfaces derived from theoretical simulations quantitatively identified the hydrogen bond types and allowed the evolution of hydrogen bonds to be visualized in diverse acid-base interaction complexes during proton transfer. Our findings provide a new perspective to reveal the nature and evolution of hydrogen bonds and confirm the superiority of 2D NMR techniques in identifying the subtle distinctions of various hydrogen-bonding configurations.

Phylogeny more than plant height and leaf area explains variance in seed mass.

Although variation in seed mass can be attributed to other plant functional traits such as plant height, leaf size, genome size, growth form, leaf N and phylogeny, until now, there has been little information on the relative contributions of these factors to variation in seed mass. We compiled data consisting of 1071 vascular plant species from the literature to quantify the relationships between seed mass, explanatory variables and phylogeny. Strong phylogenetic signals of these explanatory variables reflected inherited ancestral traits of the plant species. Without controlling phylogeny, growth form and leaf N are associated with seed mass. However, this association disappeared when accounting for phylogeny. Plant height, leaf area, and genome size showed consistent positive relationship with seed mass irrespective of phylogeny. Using phylogenetic partial R2s model, phylogeny explained 50.89% of the variance in seed mass, much more than plant height, leaf area, genome size, leaf N, and growth form explaining only 7.39%, 0.58%, 1.85%, 0.06% and 0.09%, respectively. Therefore, future ecological work investigating the evolution of seed size should be cautious given that phylogeny is the best overall predictor for seed mass. Our study provides a novel avenue for clarifying variation in functional traits across plant species, improving our better understanding of global patterns in plant traits.

Controlling Metal-Oxide Reducibility for Efficient C-H Bond Activation in Hydrocarbons.

Knowing the structure of catalytically active species/phases and providing methods for their purposeful generation are two prerequisites for the design of catalysts with desired performance. Herein, we introduce a simple method for precise preparation of supported/bulk catalysts. It utilizes the ability of metal oxides to dissolve and to simultaneously precipitate during their treatment in an aqueous ammonia solution. Applying this method for a conventional VOx -Al2 O3 catalyst, the concentration of coordinatively unsaturated Al sites was tuned simply by changing the pH value of the solution. These sites affect the strength of V-O-Al bonds of isolated VOx species and thus the reducibility of the latter. This method is also applicable for controlling the reducibility of bulk catalysts as demonstrated for a CeO2 -ZrO2 -Al2 O3 system. The application potential of the developed catalysts was confirmed in the oxidative dehydrogenation of ethylbenzene to styrene with CO2 and in the non-oxidative propane dehydrogenation to propene. Our approach is extendable to the preparation of any metal oxide catalysts dissolvable in an ammonia solution.

Modulating the Microenvironment of Silanols in Pure-Silicon Zeolites for Boosting Vapor-phase Beckmann Rearrangement of Cyclohexanone Oxime.

Vapor-phase Beckmann rearrangement of cyclohexanone oxime (CHO) to ε-caprolactam (CPL) is still difficult to commercialize at the industrial scale due to its relatively low catalytic activity and poor lifetime. Herein, we synthesized a series of pure-silicon zeolites (including MFI, MEL, and -SVR) with three-dimensional 10-member-ring topolgies, diverse silanol status, and hierarchical porosity to investigate the synergistic effects of inner diffusivity and reactivity. S-1 zeolite of MFI-type topology with plentiful silanol nests exhibits a more preferable catalytic performance in terms of CHO conversion (99.7%) and CPL selectivity (89.7%), much higher than those of MEL- and -SVR-type zeolites mainly due to their diverse silanol distribution. With the construction of hierarchical porosity, S-1-P shows improved CPL selectivity of 94.1% owing to the enhanced diffusivity to shorten the retention time of the reactant and product molecules. The reaction mechanism and network have been further revealed by density functional theory (DFT) calculations and experimental designs, which indicate that silanol nests are major active sites due to their suitable interaction with CHO rather than terminal silanols. Particularly, the microenvironments of silanols can be modulated by alcohol solvents, ascribed to their different charge transfer and steric hindrance. Consequently, S-1-P shows superior CPL selectivity of 97.3% in ethonal solvents, which have higher adsorb energy of -0.627 eV with silanol nests than other alcohols. The present study not only provides a fundamental guide for the design of zeolite catalysts but also provides a reference for modulating the microenvironment of active sites according to the catalytic mechanism.

Versatile Synthesis of Hollow-Structured Mesoporous Carbons by Enhanced Surface Interaction for High-Performance Lithium-Ion Batteries.

Nanoporous carbons are very attractive for various applications including energy storage. Templating methods with assembled amphiphilic molecules or porous inorganic templates are typically used for the synthesis. Amongst the different members of this family, CMK-5-like structures that are constructed to consist of sub-10 nm amorphous carbon nanotubes and ultrahigh specific surface area due to their thin pore walls, have the best properties in various respects. However, the fabrication of such hollow-structured mesoporous carbons entails elaborately tailoring the surface properties of the template pore walls and selecting specific carbon precursors. Thus, very limited cases are successful. Herein, a versatile and general silanol-assisted surface-casting method to create hollow-structured mesoporous carbons and heteroatom-doped derivatives with numerous organic molecules (e.g., furfuryl alcohol, resol, 2-thiophene methanol, dopamine, tyrosine) and different structural templates is reported. These carbon materials exhibit ultrahigh surface area (2400 m2  g-1 ), large pore volume (4.0 cm3  g-1 ), as well as satisfactory lithium-storage capacity (1460 mAh g-1 at 0.1 A g-1 ), excellent rate capability (320 mAh g-1 at 5 A g-1 ), and very outstanding cycling performance (2000 cycles at 5 A g-1 ).

Rhodium nanoparticles supported on silanol-rich zeolites beyond the homogeneous Wilkinson's catalyst for hydroformylation of olefins.

Hydroformylation is one of the largest industrially homogeneous processes that strongly relies on catalysts with phosphine ligands such as the Wilkinson's catalyst (triphenylphosphine coordinated Rh). Heterogeneous catalysts for olefin hydroformylation are highly desired but suffer from poor activity compared with homogeneous catalysts. Herein, we demonstrate that rhodium nanoparticles supported on siliceous MFI zeolite with abundant silanol nests are very active for hydroformylation, giving a turnover frequency as high as ~50,000 h-1 that even outperforms the classical Wilkinson's catalyst. Mechanism study reveals that the siliceous zeolite with silanol nests could efficiently enrich olefin molecules to adjacent rhodium nanoparticles, enhancing the hydroformylation reaction.

Behavioral adaptation of sympatric rodents to early germination of oak acorns: radicle pruning and embryo excision.

The seed germination schedule is a key factor affecting the food-hoarding behavior of animals and the seedling regeneration of plants. However, little is known about the behavioral adaptation of rodents to the rapid germination of acorns. In this study, we provided Quercus variabilis acorns to several rodent species to investigate how food-hoarding animals respond to seed germination. We found that only Apodemus peninsulae adopted embryo excision behavior to counteract seed germination, which is the first report of embryo excision in nonsquirrel rodents. We speculated that this species may be at an early stage of the evolutionary response to seed perishability in rodents, given the low rate of embryo excision in this species. On the contrary, all rodent species preferred to prune the radicles of germinating acorns before caching, suggesting that radicle pruning is a stable and more general foraging behavior strategy for food-hoarding rodents. Furthermore, scatter-hoarding rodents preferred to scatter-hoard and prune more germinating acorns, whereas they consumed more nongerminating acorns. Acorns with embryos excised rather than radicles pruned were much less likely to germinate than intact acorns, suggesting a behavioral adaptation strategy by rodents to the rapid germination of recalcitrant seeds. This study provides insight into the impact of early seed germination on plant-animal interactions.

High rodent abundance increases seed removal but decreases scatter-hoarding and seedling recruitment along an elevational gradient.

The distributions of small rodents in mountainous environments across different elevations can provide important information regarding the effects of climate change on the dispersal of plant species. However, few studies of oak forest ecosystems have compared the elevational patterns of sympatric rodent diversity, seed dispersal, seed bank, and seedling abundance. Thus, we tested the differences in the seed disperser composition and abundance, seed dispersal, seed bank abundance, and seedling recruitment for Quercus wutaishanica along 10 elevation levels in the Taihang Mountains, China. Our results provide strong evidence that complex asymmetric seed dispersal and seedling regeneration exist along an elevational gradient. The abundance of rodents had a significant negative correlation with the elevation and the seed removal rates peaked and then declined with increasing elevation. The seed removal rates were higher at middle and lower elevations than higher elevations but acorns were predated by 5 species of seed predators at middle and lower elevations, and thus, there was a lower likelihood of recruitment compared with those dropped beneath mother oaks at higher elevations. More importantly, the number of individual seeds in the seed bank and seedlings increased with the elevation, although dispersal services were reduced at sites lacking rodents. As conditional mutualists, the rodents could possibly act as antagonistic seed predators rather than mutualistic seed dispersers at low and middle elevations, thereby resulting in the asymmetric pattern of rodent and seedling abundance with increasing elevation to affect the community assembly and ecosystem functions on a large spatial scale.

Comparison of gut bacterial communities of Hyphantriacunea Drury (Lepidoptera, Arctiidae), based on 16S rRNA full-length sequencing.

There are a large number of microorganisms in the gut of insects, which form a symbiotic relationship with the host during the long-term co-evolution process and have a significant impact on the host's nutrition, physiology, development, immunity, stress tolerance and other aspects. However, the composition of the gut microbes of Hyphantriacunea remains unclear. In order to investigate the difference and diversity of intestinal microbiota of H.cunea larvae feeding on different host plants, we used PacBio sequencing technology for the first time to sequence the 16S rRNA full-length gene of the intestinal microbiota of H.cunea. The species classification, ß diversity and function of intestinal microflora of the 5th instar larvae of four species of H.cunea feeding on apricot, plum, redbud and Chinese ash were analysed. The results showed that a total of nine phyla and 65 genera were identified by PacBio sequencing, amongst which Firmicutes was the dominant phylum and Enterococcus was the dominant genus, with an average relative abundance of 59.29% and 52.16%, respectively. PERMANOVA analysis and cluster heat map showed that the intestinal microbiomes of H.cunea larvae, fed on different hosts, were significantly different. LEfSe analysis confirmed the effect of host diet on intestinal community structure and PICRUSt2 analysis showed that most of the predictive functions were closely related to material transport and synthetic, metabolic and cellular processes. The results of this study laid a foundation for revealing the interaction between the intestinal microorganisms of H.cunea and its hosts and provided ideas for exploring new green prevention and control strategies of H.cunea.