Metal-organic frameworks (MOFs) are typically built by assembly of metal centres and organic linkers, and have emerged as promising crystalline materials in a variety of fields. However, the stability of MOFs is a key limitation for their practical applications. Herein, we report a novel Sr 2+: -MOF [Sr4(Tdada)2(H2O)3(DMF)2] (denoted as NKU- 105: , NKU = Nankai University; H4Tdada = 5,5'-((thiophene-2,5-dicar bonyl)bis(azanediyl))diisophthalic acid; DMF = N,N-dimethylformamide) featuring an open square channel of about 6 Å along the c-axis. Notably, NKU- 105: exhibits much outstanding chemical stability against common organic solvents, boiling water, acids and bases, relative to most MOF materials. Furthermore, NKU- 105: is an environment-friendly luminescent material with a bright cyan emission.This article is part of the themed issue 'Coordination polymers and metal-organic frameworks: materials by design'.
Abstract Hydrologically mediated hot moments (HM‐HMs) of transient anomalous diffusion (TAD) denote abrupt shifts in hydraulic conditions that can profoundly influence the dynamics of anomalous diffusion for pollutants within heterogeneous aquifers. How to efficiently model these complex dynamics remains a significant challenge. To bridge this knowledge gap, we propose an innovative model termed “the impulsive, tempered fractional advection‐dispersion equation” (IT‐fADE) to simulate HM‐HMs of TAD. The model is approximated using an L1‐based finite difference solver with unconditional stability and an efficient convergence rate. Application results demonstrate that the IT‐fADE model and its solver successfully capture TAD induced by hydrologically trigged hot phenomena (including hot moments and hot spots) across three distinct aquifers: (a) transient sub‐diffusion arising from sudden shifts in hydraulic gradient within a regional‐scale alluvial aquifer, (b) transient sub‐ or super‐diffusion due to convergent or push‐pull tracer experiments within a local‐scale fractured aquifer, and (c) transient sub‐diffusion likely attributed to multiple‐conduit flow within an intermediate‐scale karst aquifer. The impulsive terms and fractional differential operator integrated into the IT‐fADE aptly capture the ephemeral nature and evolving memory of HM‐HMs of TAD by incorporating multiple stress periods into the model. The sequential HM‐HM model also characterizes breakthrough curves of pollutants as they encounter hydrologically mediated, parallel hot spots. Furthermore, we delve into discussions concerning model parameters, extensions, and comparisons, as well as impulse signals and the propagation of memory within the context of employing IT‐fADE to capture hot phenomena of TAD in aquatic systems.
Two Zn(ii)-MOFs based on pyrazole functionalized carboxylic ligands have been constructed, which exhibit favorable selective adsorption of organic cationic dyes.
ABSTRACT Soil is the natural habitat for microorganisms, providing water and nutrients for vegetation, but the influence of meadow degradation on the “vegetation‐soil‐microorganism” system is still controversial, and the drivers of soil microbial and vegetation characteristics change are still unclear. This study explores in‐depth the vegetation and soil changes in four different degradation levels, that is, non‐degraded (ND), lightly degraded (LD), moderately degraded (MD), and severely degraded (SD), in the northeastern region of the Qinghai‐Tibetan Plateau. Soil metagenomic sequencing methods were employed to understand the soil microbial and functional diversity and the factors that influence them. The findings indicated that alpine meadow degradation decreased the vegetation height, coverage, and above‐ground biomass (AGB), but increased the vegetation diversity index. In addition, meadow degradation reduces soil properties (organic carbon, total nitrogen and phosphorus, available nitrogen and phosphorus) and enzyme activities (sucrase, cellulase, urease, and catalase) but increases soil pH. The copiotrophic groups (Actinobacteria, Ascomycota) decreased while oligotrophic groups (Acidobacteria, Glomeromycota) increased with meadow degradation. In particular, changes in vegetation characteristics and microbial community structure in alpine meadows are strongly influenced by changes in soil pH. In conclusion, the degradation of alpine meadows leads to the growth of some barren‐tolerant species and deviation of soil pH from neutrality, which increases vegetation diversity but surface exposure reduces the vegetation richness, affects the type and amount of root secretions and changes in soil microbial communities, which reduce the fixation and release of soil nutrients. This study provides the theoretical basis for further analyzing the inner mechanism of alpine meadow degradation.
Contact-electrification is a universal effect for all existing materials, but it still lacks a quantitative materials database to systematically understand its scientific mechanisms. Using an established measurement method, this study quantifies the triboelectric charge densities of nearly 30 inorganic nonmetallic materials. From the matrix of their triboelectric charge densities and band structures, it is found that the triboelectric output is strongly related to the work functions of the materials. Our study verifies that contact-electrification is an electronic quantum transition effect under ambient conditions. The basic driving force for contact-electrification is that electrons seek to fill the lowest available states once two materials are forced to reach atomically close distance so that electron transitions are possible through strongly overlapping electron wave functions. We hope that the quantified series could serve as a textbook standard and a fundamental database for scientific research, practical manufacturing, and engineering.
A 2D network 1 was synthesized. After immersing 1 in benzene homologues, the crystal structures of 2 and 3 were gotten, demonstrating that the introduction of benzene homologues has transformed the π–π packing mode, further altering the host framework and fluorescence performance.
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