Consecutive Single-Crystal-to-Single-Crystal Isomerization of Novel Octamolybdate Anions within a Microporous Hybrid Framework with Robust Water Sorption Properties

The 3D hybrid framework [{Cu(cyclam)}₃(κ-Mo₈O₂₇)] ⋅ 14H₂O ( 1 ) (cyclam=1,4,8,11-tetraazacyclotetradecane) undergoes sequential single-crystal-to-single-crystal transformations upon heating to afford two different anhydrous phases ( 2 a and 3 a ). These transitions modify the framework dimensionality and enable the isomerization of κ-octamolybdate (κ-Mo₈) anions into λ ( 2 a ) and μ ( 3 a ) forms through metal migration. Hydration of 3 a involves condensation of one water molecule to the cluster to afford the γ-Mo₈ isomer in 4 , which dehydrates back into 3 a through the 6 a intermediate. In contrast, 2 a reversibly hydrates to form 5 , exhibiting the same Mo₈ cluster as that of 1 . It is remarkable that three of the Mo₈ clusters (κ, λ and μ) are new and that up to three different microporous phases can be isolated from 1 ( 2 a , 3 a , and 6 a ). Water vapor sorption analyses show high recyclability and the highest uptake values for POM-based systems. The isotherms display an abrupt step at low humidity level desirable for humidity control devices or water harvesting in drylands.     

Active Sites Decorated Nonpolar Pore-Based MOF for One-step Acquisition of C2H4 and Recovery of C3H6

Herein, a 2-fold interpenetrated metal-organic framework (MOF) Zn-BPZ-TATB with accessible N/O active sites in nonpolar pore surfaces was reported for one-step C₂H₄ purification from C₂H₆ or C₃H₆ mixtures as well as recovery of C₃H₆ from C₂H₆/C₃H₆/C₂H₄ mixtures. The MOF exhibits the favorable C₂H₆ and C₃H₆ uptakes (>100 cm³ g⁻¹ at 298 K under 100 kPa) as well as selective adsorption of C₂H₆ and C₃H₆ over C₂H₄. The C₃H₆- and C₂H₆-selective feature were investigated detailedly by experimental tests as well as sorption kinetic studyies. Molecular modelling revealed the multiple interactions between C₃H₆ or C₂H₆ molecules and methyl groups as well as triazine rings in pores. Zn-BPZ-TATB not only can directly generate 323.4 L kg⁻¹ and 15.4 L kg⁻¹ of high-purity (≥99.9 %) C₂H₄ from C₃H₆/C₂H₄ and C₂H₆/C₂H₄ mixtures, but also provide a large high-purity (≥99.5 %) C₃H₆ recovery capacity of 60.1 L kg⁻¹ from C₃H₆/C₂H₄ mixtures. More importantly, the high-purity C₃H₆ (≥99.5 %) and C₂H₄ (≥99.9 %) with the productivities of 38.2 and 12.7 L kg⁻¹ can be simultaneously obtained from C₂H₆/C₃H₆/C₂H₄ mixtures through a single adsorption/desorption cycle.     

Bulk Mn2+ Doped 1D Hybrid Lead Halide Perovskite with Highly Efficient,Tunable and Stable Broadband Light Emissions

Mn²⁺ doped colloidal three-dimensional (3D) lead halide perovskite nanocrystal (PNC) has attracted intensive research attention; however, the low exciton binding energy and fatal optical instability of 3D PNC seriously hinder the optoelectronic application. Therefore, it remains significant to explore new stable host perovskite with strongly bound exciton to realize more desirable luminescent property. In this work, we utilized bulk one-dimensional (1D) hybrid perovskite of [AEP]PbBr₅ ⋅ H₂O (AEP=N-aminoethylpiperazine) as structural platform to rationally optimize the luminescent property by a controllable Mn²⁺ doping strategy. Significantly, the series of Mn²⁺-doped 1D [AEP]PbBr₅ ⋅ H₂O show enhanced energy transfer efficiency from the strongly bound excitons of host material to 3d electrons of Mn²⁺ ions, resulting in tunable broadband light emissions from weak yellow to strong red spectral range with highest photoluminescence quantum yield up to 28.41 %. More importantly, these Mn²⁺-doped 1D perovskites display ultrahigh structural and optical stabilities in humid atmosphere, water and high temperature exceeding the conventional 3D PNC. Combined highly efficient, tunable and stable broadband light emissions enable Mn²⁺-doped 1D perovskite as excellent down-converting phosphor showcasing the potential application in white light emitting diode. This work not only provides a profound understanding of low-dimensional perovskites but also opens a new way to rationally design high-performance broadband light emitting perovskites for solid-state lighting and displaying devices.     

三维无机-有机杂化微孔化合物[Zn3(BTC)2(H2O)3]n的合成与结构

传统的沸石和分子筛微孔晶体材料是指以硅酸盐、硅铝酸盐、磷铝酸盐和无机金属磷酸盐为骨架的晶体材料^[1,2].     

A Water Stable CdII‐based Metal‐Organic Framework as a Multifunctional Sensor for Selective Detection of Cu2+ and Cr2O72– Ions

A water stable tetrazolate‐containing metal‐organic framework, [Cd₂(L)(OH)(H₂O)₂]_n ( 1 ) [H₃L = 5‐(4‐(tetrazol‐5‐yl)phenyl)isophthalic acid], was synthesized under solvothermal conditions and structurally characterized. Compound 1 displays a three dimensional porous network with one dimensional tubular channels based on trinuclear cluster [Cd₃(μ₃‐OH)N₄C] units. Notably, 1 exhibits highly sensitive response to Cu²⁺ and Cr₂O₇^2– through luminescence quenching effects with the detection limit of 0.666 ppm for Cu²⁺ and 0.846 ppm for Cr₂O₇^2–, respectively. The possible mechanism of the luminescence quenching was discussed in detail.     

CeO2/TiO2 Monolith Catalyst for the Selective Catalytic Reduction of NOx with NH3: Influence of H2O and SO2

The influences of H₂O and SO₂ on CeO₂/TiO₂ monolith catalyst for the selective catalytic reduction(SCR) of NO_x with NH₃ were investigated. In the absence of SO₂, H₂O inhibited the SCR activity, which might be ascribed to the competitive adsorption of H₂O and reactants such as NH₃ and/or NO_x. SO₂ could promote the SCR activity of CeO₂/TiO₂ monolith catalyst in the absence of H₂O, while in the presence of H₂O it speeded the deactivation. During the SCR reaction in SO₂-containing gases, Ce(III) sulfate species formed on the catalyst surface, resulting in the enhancement of Brønsted acidity. This played a significant role in the enhanced SCR activity. However, in the presence of both H₂O and SO₂, a large amount of ammonium-sulfate salts formed on the catalyst surface, which resulted in the blocking of catalyst pores and deactivated the catalyst. In addition, the NO_x conversion was more sensitive to gas hourly space velocity in the presence of H₂O than in the absence of H₂O. The relatively high space velocity would result in a higher formation rate of ammonium-sulfate salts on per unit catalyst in the presence of H₂O and SO₂, which caused obvious deactivation of Ce/TiO₂ monolith catalyst.     

Facilely Tuning Porous NiCo2O4 Nanosheets with Metal Valence‐State Alteration and Abundant Oxygen Vacancies as Robust Electrocatalysts Towards Water Splitting

Great efforts in developing clean electrochemical water splitting technology leads to the rational design and synthesis of highly efficient oxygen evolution reaction (OER) catalysts with low overpotential and fast reaction kinetics. Herein, we focus on the role that morphology and composition play in the OER performance to rationally design freestanding 3D porous NiCo₂O₄ nanosheets with metal valence states alteration and abundant oxygen vacancies as robust electrocatalysts towards water splitting. Besides metal valence‐state alteration, surface modification regarding the evolution of oxygen vacancies is facilely realized upon the sodium borohydride treatment, which is beneficial for the enhanced OER performance. Taking advantage of the porous nanostructures and abundant surface activity sites with high reactivity, the resultant nanostructures exhibit excellent OER activity and stability in alkaline electrolytes that outperform that of pristine NiCo₂O₄ and commercial RuO₂, thus holding great potential for the water splitting.     

A Molecular Z-Scheme Artificial Photosynthetic System Under the Bias-Free Condition for CO2 Reduction Coupled with Two-electron Water Oxidation: Photocatalytic Production of CO/HCOOH and H2O2

Bio-inspired molecular-engineered systems have been extensively investigated for the half-reactions of H₂O oxidation or CO₂ reduction with sacrificial electron donors/acceptors. However, there has yet to be reported a device for dye-sensitized molecular photoanodes coupled with molecular photocathodes in an aqueous solution without the use of sacrificial reagents. Herein, we will report the integration of Sn^IV- or Al^III-tetrapyridylporphyrin (SnTPyP or AlTPyP) decorated tin oxide particles (SnTPyP/SnO₂ or AlTPyP/SnO₂) photoanode with the dye-sensitized molecular photocathode on nickel oxide particles containing [Ru(diimine)₃]²⁺ as the light-harvesting unit and [Ru(diimine)(CO)₂Cl₂] as the catalyst unit covalently connected and fixed within poly-pyrrole layer (RuCAT-RuC₂-PolyPyr-PRu/NiO). The simultaneous irradiation of the two photoelectrodes with visible light resulted in H₂O₂ on the anode and CO, HCOOH, and H₂ on the cathode with high Faradaic efficiencies in purely aqueous conditions without any applied bias is the first example of artificial photosynthesis with only two-electron redox reactions.     

Porous Al2O3/Al Metal Ceramics Prepared by the Oxidation of Aluminum Powder under Hydrothermal Conditions Followed by Thermal Dehydration: III. The Reactivity of Aluminum,the Reaction Mechanism of Its Oxidation with Water Vapor,and the Microtexture of Cermets

The macrokinetics of aluminum oxidation under hydrothermal conditions at 150–250°C and water vapor pressures of 0.5–4.5 MPa was studied. The apparent kinetic characteristics of the process were determined. The diffusion of water through the layer of a hydrated product was found to be a rate-limiting step. It was found that diffusion coefficients for various aluminum samples differed by almost two orders of magnitude; the main reaction steps were revealed. Changes in the texture of aluminum oxide in cermets in the course of the hydrothermal oxidation reaction were analyzed. This texture was found to depend on the ratio between the specific rate of the oxidation reaction and the rate of aging of the oxidation products under hydrothermal conditions.