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The efficient employment of chiral porous organic cages (POCs) for asymmetric catalysis is of great significance. In this work, we have synthesized a chiral N-rich organic cage constructed through chiral (S, S)-1,2-cyclohexanediamine and benzene-1,3,5-tricarbaldehyde utilizing dynamic imine chemistry according to the literature. Following reduction with NaBH4, the resulting amine-based POCs (RCC3) feature appended chiral diamine moieties capable of coordinating Cu2+ cations. This Cu2+ coordination provides RCC3 with excellent enantioselectivity as a supramolecular nanoreactor in asymmetric decarboxylative Mannich reactions, providing up to 94% ee of the product. We found that the spatial distribution of chiral amine sites and the coordination of Cu2+ in the RCC3 have a significant impact on catalytic activity, especially enantioselectivity. This work provides insights into the structure–function relationship within supramolecular catalytic systems

There is a wide range of naturally regenerated Morus alba in the declining Robinia pseudoacacia plantation of the Yellow River Delta. It is important to clarify the key mechanism of natural regeneration of M. alba for the transformation of declining R. pseudoacacia plantation. According to the death density of R. pseudoacacia, the plantation of R. pseudoacacia was divided into nondeclining, moderately declining, and severely declining forests. The structural characteristics of adult trees and seedlings of M. alba in different decline degrees forest were investigated. A pot experiment was conducted to study the seed germination and early seedling growth of M. alba in saline alkali soil and nonsaline alkali soil under different soil salt contents and light intensities. The results showed that the natural regeneration of M. alba was obviously affected by the decline of R. pseudoacacia plantation. With the increase of decline degree, M. alba density and seedling density first increased and then decreased, and were the highest in the medium decline plantation. Under full light intensity, the vigor index of M. alba seeds and the biomass of seedlings were significantly greater than those of 25% full light intensity. The germination rate and germination index under 1‰ soil salt content were significantly lower than those under 3‰, but the biomass of seedlings was on the contrary. The 1000-seed weight, seed germination, and seedling biomass of moderately declining R. pseudoacacia plantations were close to those of nonsaline alkali land, while significantly higher than those of nondeclining plantations, but the germination index of moderately declining R. pseudoacacia plantation was higher than that of nonsaline alkali land. Therefore, the germination ability of maternal trees in saline alkali land was higher than that in nonsaline alkali land under salt stress.

Two-dimensional materials with monolayer thickness and extreme aspect ratios are sought for their high surface areas and unusual physicochemical properties 1 . Liquid exfoliation is a straightforward and scalable means of accessing such materials 2 , but has been restricted to sheets maintained by strong covalent, coordination or ionic interactions 3 – 10 . The exfoliation of molecular crystals, in which repeat units are held together by weak non-covalent bonding, could generate a greatly expanded range of two-dimensional crystalline materials with diverse surfaces and structural features. However, at first sight, these weak forces would seem incapable of supporting such intrinsically fragile morphologies. Against this expectation, we show here that crystals composed of discrete supramolecular coordination complexes can be exfoliated by sonication to give free-standing monolayers approximately 2.3 nanometres thick with aspect ratios up to approximately 2,500:1, sustained purely by apolar intermolecular interactions. These nanosheets are characterized by atomic force microscopy and high-resolution transmission electron microscopy, confirming their crystallinity. The monolayers possess complex chiral surfaces derived partly from individual supramolecular coordination complex components but also from interactions with neighbours. In this respect, they represent a distinct type of material in which molecular components are all equally exposed to their environment, as if in solution, yet with properties arising from cooperation between molecules, because of crystallinity. This unusual nature is reflected in the molecular recognition properties of the materials, which bind carbohydrates with strongly enhanced enantiodiscrimination relative to individual molecules or bulk three-dimensional crystals. Sonication of layered metallacycle crystals gives free-standing nanosheets held together by weak non-covalent interactions, with chiral surfaces that show improved binding and enantiodiscrimination compared with individual metallacycle molecules.

In this study, SiO[sub.2]@MIL-88A(Fe) core–shell microspheres were successfully synthesized through a simple immobilization method for dye degradation via an MIL-88A(Fe)-mediated Fenton-like process. These microspheres were fabricated by in situ immobilizing MIL-88A(Fe) onto mesoporous organosilane spheres functionalized with -COOH groups. Structural analyses and characterizations confirmed the formation of well-defined MOF particles anchored on the silicate microspheres, with electron microscopy verifying their porous core–shell structure. The newly developed core–shell materials achieved a high degree of dye degradation, reaching up to 96% for 10 mg/L dye solutions in neutral aqueous conditions within 30 min at room temperature through the Fenton-like process. Furthermore, SiO[sub.2]@MIL-88A(Fe) exhibited excellent stability and recyclability, maintaining its performance over at least seven reuse cycles with minimal loss of activity. This material is easy to synthesize as well as cost-effective and demonstrates significant potential for wastewater purification involving a range of four different dyes.

In this study, SiO2@MIL-88A(Fe) core–shell microspheres were successfully synthesized through a simple immobilization method for dye degradation via an MIL-88A(Fe)-mediated Fenton-like process. These microspheres were fabricated by in situ immobilizing MIL-88A(Fe) onto mesoporous organosilane spheres functionalized with -COOH groups. Structural analyses and characterizations confirmed the formation of well-defined MOF particles anchored on the silicate microspheres, with electron microscopy verifying their porous core–shell structure. The newly developed core–shell materials achieved a high degree of dye degradation, reaching up to 96% for 10 mg/L dye solutions in neutral aqueous conditions within 30 min at room temperature through the Fenton-like process. Furthermore, SiO2@MIL-88A(Fe) exhibited excellent stability and recyclability, maintaining its performance over at least seven reuse cycles with minimal loss of activity. This material is easy to synthesize as well as cost-effective and demonstrates significant potential for wastewater purification involving a range of four different dyes.

Groundwater plays a significant role in influencing the growth and distribution of Robinia pseudoacacia L. plantations, with the largest planting area in the Yellow River Delta, by affecting the soil water–salt environment. This study aimed to clarify the mechanism of groundwater’s influence on the growth of R. pseudoacacia under different levels of groundwater mineralization (GWM) and groundwater depth (GWD). We simulated GWM of 0, 2 and 4 g L−1, and GWD of 0.8, 1.3 and 1.8 m. As GWM increased, soil relative water content (SRWC) and soil salt (dissolved salt) content (SSC) increased; sapling biomass (SB), stem mass (SM), leaf mass (LM), photosynthesis characteristics (maximum net photosynthetic rate (Pn), stomatal conductance (gs), intercellular CO2 concentration (Ci), transpiration rate (E) and water use efficiency (WUE)) decreased; root mass (RM), root mass ratio (RMR) and root–shoot ratio (RSR) first increased then decreased; stem mass ratio (SMR) first decreased then increased; and leaf mass ratio (LMR) increased. As GWD increased, SRWC decreased, but SSC first increased then decreased; SB, RM, RMR, RSR, and photosynthesis characteristics increased; SM and LM first increased then decreased; and SMR and LMR decreased. SRWC and SSC were negatively correlated with SB and photosynthesis characteristics. SRWC was negatively correlated with RMR and RSR, whereas it was positively correlated with LMR. SSC was negatively correlated with SMR, whereas it was positively correlated with LMR. The first principal component, including SB, RM, and photosynthesis characteristics, was related to sapling growth. The second principal component, including RMR, SMR, and RSR, was mainly related to biomass allocation. In conclusion, GWM and GWD affected the soil water and salt content, which were key factors influencing the photosynthesis and growth of R. pseudoacacia. Adjustments in biomass allocation and photosynthesis were the main adaptive strategies of R. pseudoacacia to salt, drought, and flooding stress.

The construction of a high stability heterogeneous catalyst for privileged common catalysis is a benefit in regard to reuse and separation. Herein, a palladium diphenylphosphine-based hollow-shell-structured mesoporous catalyst (HS@PdPPh2@MSN) was prepared by immobilizing bis((diphenylphosphino)ethyltriethoxysilane)palladium acetate onto the inner wall of a mesoporous organicsilicane hollow shell, whose surface was protected by a –Si(Me)3 group. Electron microscopies confirmed its hollow-shell-structure, and structural analyses and characterizations revealed its well-defined single-site active species within the silicate network. As presented in this study, the newly constructed HS@PdPPh2@MSN enabled an efficient Suzuki-Miyaura cross-coupling reaction for varieties of substrates with up to 95% yield in mild conditions. Meanwhile, it could be reused at least five times with good activity, indicating its excellent stability and recyclability. Furthermore, the cost-effective and easily synthesized HS@PdPPh2@MSN made it a good candidate for employment in fine chemical engineering.

Groundwater plays a significant role in influencing the growth and distribution of Robinia pseudoacacia L. plantations, with the largest planting area in the Yellow River Delta, by affecting the soil water–salt environment. This study aimed to clarify the mechanism of groundwater’s influence on the growth of R. pseudoacacia under different levels of groundwater mineralization (GWM) and groundwater depth (GWD). We simulated GWM of 0, 2 and 4 g L[sup.−1], and GWD of 0.8, 1.3 and 1.8 m. As GWM increased, soil relative water content (SRWC) and soil salt (dissolved salt) content (SSC) increased; sapling biomass (SB), stem mass (SM), leaf mass (LM), photosynthesis characteristics (maximum net photosynthetic rate (P[sub.n]), stomatal conductance (g[sub.s]), intercellular CO[sub.2] concentration (C[sub.i]), transpiration rate (E) and water use efficiency (WUE)) decreased; root mass (RM), root mass ratio (RMR) and root–shoot ratio (RSR) first increased then decreased; stem mass ratio (SMR) first decreased then increased; and leaf mass ratio (LMR) increased. As GWD increased, SRWC decreased, but SSC first increased then decreased; SB, RM, RMR, RSR, and photosynthesis characteristics increased; SM and LM first increased then decreased; and SMR and LMR decreased. SRWC and SSC were negatively correlated with SB and photosynthesis characteristics. SRWC was negatively correlated with RMR and RSR, whereas it was positively correlated with LMR. SSC was negatively correlated with SMR, whereas it was positively correlated with LMR. The first principal component, including SB, RM, and photosynthesis characteristics, was related to sapling growth. The second principal component, including RMR, SMR, and RSR, was mainly related to biomass allocation. In conclusion, GWM and GWD affected the soil water and salt content, which were key factors influencing the photosynthesis and growth of R. pseudoacacia. Adjustments in biomass allocation and photosynthesis were the main adaptive strategies of R. pseudoacacia to salt, drought, and flooding stress.

Elucidating the influence mechanisms of seed germination and seedling growth is important for revealing the natural regeneration of forest plantations. We collected the seeds from 58-year-old Quercus acutissima Carruth. forest, and the seeds were further divided into three classes: large, medium, and small, and sown under the forest gaps (I, 197.82 m2; II, 91.85 m2, III, understory) to observe seed germination and early seedling growth. Precipitation in the study area and soil moisture content in the forest gaps were also observed during the trial period. The results showed that the precipitation in 2019 was similar to that in 2020; both were significantly lower than the precipitation in 2021. The difference in soil water content between gaps I and II was not significant, and both were significantly lower than III. The order of seedling emergence rate in gaps was II > III > I, but the minimum was almost close to zero in I. Large and medium seeds showed significantly greater emergence rate than small seeds. The seedlings of II had higher seedling height, ground diameter, ground diameter relative growth rate, seedling biomass, root surface area, and root volume than those of III. Large seeds had the highest ground diameter, ground diameter relative growth rate, biomass, root mass ratio, root shoot ratio, and root surface area. Correlation analysis showed that seedling biomass was significantly and positively correlated with root surface area and root volume, and significantly and negatively correlated with specific root length and specific root surface area. The regulation of soil moisture in the gap and the adaptability related to seed size were two key factors influencing the seed germination and early seedling growth of Q. acutissima.

There is a wide range of naturally regenerated Morus alba in the declining Robinia pseudoacacia plantation of the Yellow River Delta. It is important to clarify the key mechanism of natural regeneration of M. alba for the transformation of declining R. pseudoacacia plantation. According to the death density of R. pseudoacacia, the plantation of R. pseudoacacia was divided into nondeclining, moderately declining, and severely declining forests. The structural characteristics of adult trees and seedlings of M. alba in different decline degrees forest were investigated. A pot experiment was conducted to study the seed germination and early seedling growth of M. alba in saline alkali soil and nonsaline alkali soil under different soil salt contents and light intensities. The results showed that the natural regeneration of M. alba was obviously affected by the decline of R. pseudoacacia plantation. With the increase of decline degree, M. alba density and seedling density first increased and then decreased, and were the highest in the medium decline plantation. Under full light intensity, the vigor index of M. alba seeds and the biomass of seedlings were significantly greater than those of 25% full light intensity. The germination rate and germination index under 1‰ soil salt content were significantly lower than those under 3‰, but the biomass of seedlings was on the contrary. The 1000-seed weight, seed germination, and seedling biomass of moderately declining R. pseudoacacia plantations were close to those of nonsaline alkali land, while significantly higher than those of nondeclining plantations, but the germination index of moderately declining R. pseudoacacia plantation was higher than that of nonsaline alkali land. Therefore, the germination ability of maternal trees in saline alkali land was higher than that in nonsaline alkali land under salt stress.