Construction and visible-light photocatalytic performance of carboxyethyltin/transition metal–functionalized wheel-like tungstophosphates

The wheel-like tungstophosphate ([P₈W₄₈O₁₈₄]⁴⁰⁻, abbreviated as P₈W₄₈) reacted with estertin trichloride (Cl₃SnRCH₃, R = CH₂CH₂COO) in aqueous solution, resulting in a new wheel-like polyoxometalate (POM) containing six SnR fragments, formulated as K₆Na₂₄[{(SnR(H₂O))₂(μ-OH)(μ-SnR(H₂O))}₂(P₈W₄₈O₁₈₄)]·59H₂O (abbreviated as Sn ₆ - P ₈ W ₄₈ ). Based on this, the transition metal (TM) was further introduced into the Sn ₆ - P ₈ W ₄₈ system, self-assembling three other wheel-like POMs with the general formula K_xNa_yH_{26 − x − y}[{TM(H₂O)₃(SnR(H₂O))₂(μ-OH)(μ-SnR(H₂O))}₂(P₈W₄₈O₁₈₄)]·nH₂O (abbreviated as TM ₂ - Sn ₆ - P ₈ W ₄₈ , TM = Mn, Co, Ni; x = 0, 1, 2; y = 19, 22, 15; n = 72, 85, 75, respectively). The structures of these new organometal and TM co-modified compounds were characterized using infrared, UV–Vis. spectroscopy, ¹¹⁹Sn NMR, and powder- and single-crystal X-ray diffraction analysis. The estertin precursor hydrolyzed into carboxyethyltin (SnR) fragment in these crystalline POM materials, which can improve their adhesion to titanium dioxide (TiO₂). The photocatalytic performance of Sn ₆ - P ₈ W ₄₈ , TM ₂ - Sn ₆ - P ₈ W ₄₈ , and their TiO₂ composites was examined by studying the degradation of a model dye pollutant Rhodamine B (RhB) under visible-light irradiation without adding hydrogen peroxide (H₂O₂), and the photocatalytic mechanism was also discussed. The experimental results show that the title compounds exhibit a quicker and better photocatalytic degradation effect on RhB compared with their parent compound, indicating that the introduced organotin groups play a significant role. Moreover, it was found that H₂O₂ was produced after illumination pretreatment for POM solution, promoting the photocatalytic reaction.     

Metal-Mediated Directional Capping of Rod-Packing Metal–Organic Frameworks

Two new rod-packing metal–organic frameworks (RPMOF) are constructed by regulating the in situ formation of the capping agent. In CPM-s7, carboxylate linkers extend 1D manganese-oxide chains in four additional directions, forming 3D RPMOF. The substitution of Mn²⁺ with a stronger Lewis acidic Co²⁺, leads to an acceleration of the hydrolysis-prone sulfonate linker, resulting in presence of sulfate ions to reduce two out of the four carboxylate-extending directions, and thus forming a new 2D rod-packing CPM-s8. Density functional theory calculations and magnetization measurements reveal ferrimagnetic ordering of CPM-s8, signifying the potential of exploring 2D RPMOF for effective low-dimensional magnetic materials.     

Bromine-Functionalized Covalent Organic Frameworks for Efficient Triboelectric Nanogenerator

Covalent organic frameworks (COFs) enable precise integration of various organic building blocks into porous skeletons through topology predesign. Here, we report the first example of COFs by integrating electron withdrawing bromine group onto the skeletons for triboelectric nanogenerators (TENG). The resulting framework exhibits high surface area and good crystallinity. Thus, the bromine functionalized COF has more regular aligned π columns and arrays over the skeleton than bare COFs, which in turn significantly enhances charge transport ability. As a result, bromine functionalized COFs showed higher electrical output performance at 5 Hz with a peak value of short circuit current density of 43.6 μA and output voltage of 416 V, which is 2 and 1.3 times higher than those of bare COFs (21.6 μA and 318 V), respectively. These results demonstrated that this strategy for engineering electron withdrawing groups on the skeleton could open a new aspect of COFs for developing TENG devices.     

Structure elucidation and NMR assignment of two new eudesmane derivatives from Merremia yunnanensis

Two new eudesmane derivatives, 1α,6β,9β-trihydroxy-eudesm-3-ene-1-O-β-d -glucopyranoside ( 1 ) and 1α,6β,9β-trihydroxy-eudesm-3-ene-1-(6-cinnamoyl)-O-β-d -glucopyranoside ( 2 ) were discovered from Merremia yunnanensis. The structures were elucidated by analysis of their spectroscopic data including HR-ESI-MS, 1D, and 2D NMR. It should be noted that this is the first report about structure elucidation and NMR assignment of compounds from M. yunnanensis.     

Self-shaping of bioinspired chiral composites

Self-shaping materials such as shape memory polymers have recently drawn considerable attention owing to their high shape-changing ability in response to changes in ambient conditions, and thereby have promising applications in the biomedical, biosensing, soft robotics and aerospace fields. Their design is a crucial issue of both theoretical and technological interest. Motivated by the shape-changing ability of Towel Gourd tendril helices during swelling/deswelling, we present a strategy for realizing self-shaping function through the deformation of micro/nanohelices. To guide the design and fabrication of selfshaping materials, the shape equations of bent configurations, twisted belts, and helices of slender chiral composite are developed using the variation method. Furthermore, it is numerically shown that the shape changes of a chiral composite can be tuned by the deformation of micro/nanohelices and the fabricated fiber directions. This work paves a new way to create self-shaping composites.     

A Terbium Metal–Organic Framework for Highly Selective and Sensitive Luminescence Sensing of Hg2+ Ions in Aqueous Solution

A series of isomorphic lanthanide metal–organic frameworks (MOFs) Ln(TATAB)?(DMF)₄(H₂O)(MeOH)_0.5 (LnTATAB, Ln=Eu, Tb, Sm, Dy, Gd; H₃TATAB=4,4′,4′′‐s‐triazine‐1,3,5‐triyltri‐p‐aminobenzoic acid) have been solvothermally synthesized and structurally characterized. Among these MOFs, TbTATAB exhibits good water stability and a high fluorescence quantum yield. Because mercury ions (Hg²⁺) have a high affinity to nitrogen atoms, and the space between multiple nitrogen atoms from triazine and imino groups is suitable for interacting with Hg²⁺ ions, TbTATAB shows highly selective and sensitive detection of Hg²⁺ in aqueous solution with a detection limit of 4.4 nm . Furthermore, it was successfully applied to detect Hg²⁺ ions in natural water samples.     

Porphyrin‐containing Polyimide with Enhanced Light Absorption and Photocatalysis Activity

A series of porphyrin‐containing polyimide (PI) photocatalysts were synthesized by a one‐step solvothermal method. Characterization results revealed that porphyrin was uniformly coupled into the PI framework through covalent bonding and the visible‐light absorption was greatly improved. The photodegradation activity of porphyrin‐containing PIs for methyl orange (MO) under visible light was enhanced significantly, with the highest pseudo‐first‐order rate constant 35 times higher than that of neat porphyrin and 10 times higher than that of porphyrin‐free PI. The enhancement is mainly attributed to an increased light harvesting accompanied by a varied HOMO level, which was clarified by control experiments, characterizations and theoretical calculations. This work provides an insight into multiple effects of dye molecules in dye‐containing heterogeneous photocatalysts.     

Kinetics of Transesterification of Methyl Acetate and Ethanol Catalyzed by Ionic Liquid

The kinetic behavior and chemical equilibria for the transesterification of methyl acetate with ethanol to ethyl acetate and methanol catalyzed by an ionic liquid 4‐(3‐methyl‐1‐imidazolio)‐1‐butanesulfonic acid hydrogen sulfate ([HSO₃‐bmim]HSO₄) were studied experimentally. The relationship of chemical equilibrium constants versus temperature was obtained from kinetic experimental data. The effects of temperature, initial molar ratio of ethanol to methyl acetate, and catalyst concentrations were investigated. Based on the reaction mechanism, an ideal homogeneous (IH) and two nonideal homogeneous models (NIH‐1, NIH‐2) were proposed to correlate the reaction kinetic data. The activity coefficient of the catalyst was considered in NIH‐2 but not in the NIH‐1 model. The nonideal homogeneous model NIH‐1 was the best model to describe the kinetics of the transesterification reaction, and the accuracy of the reaction kinetic model is not improved by considering the effects of catalyst on the activities of the reactants and products.     

苯并咪唑类化合物的合成方法进展

苯并咪唑类化合物具有抗HIV-1、抗肿瘤、抗细胞增殖、抗寄生虫、抗炎症、抗氧化和抗癫痫方面的生物活性,因此这类化合物的合成备受化学家们的关注.首次按照反应中间体将近5年合成这类化合物的方法分为以N-亚甲基邻苯二胺(或N-亚甲基邻硝基苯胺)为中间体,以N-酰基邻苯二胺为中间体和以芳基脒(胍)为中间体三类.通过从这个角度论述这些合成方法,期望能够为设计出更好的合成方法提供启发.