CrystEngComm最新文献

Herein, cobalt is incorporated into a polyoxotungstate (POW) to obtain a new organic–inorganic hybrid Co-containing POW with a reliable 1D nanowire structure. The Co-containing POW exhibits superior oxygen evolution reaction (OER) activity in a neutral medium compared with its isomorphic Zn-containing POW, highlighting the critical role of cobalt in enhancing OER performance. This work provides a new insight into the structure–property relationship of metal oxides in electrocatalysis.

While ionothermal synthesis using deep eutectic solvents based on the combination of choline chloride and urea derivatives has been widely explored for metal–organic framework (MOF) synthesis, the alternative approach consisting in using urea derivatives on their own as solvents, albeit promising, remains comparatively underemployed. This highlight article aims to review the field of urothermal synthesis, covering the state of the art of this approach and its potential development. The use of e-urea (2-imidazolidinone, ethyleneurea), the most extensively employed species in this context, is detailed, showing its ability to play diverse roles in MOF construction. Beyond its role as solvent and soft regulator of solution acidity, it can be present in the pore or as a ligand, most commonly in a bridging mode with divalent metal cations via coordination of the carbonyl group assisted by hydrogen bonding of the NH moieties, or yield ethylenediamine as a decomposition product incorporated in the MOF. Furthermore, urothermal synthesis has demonstrated potential for the preparation of chiral architectures and their enantio-enrichment. Alternatives to e-urea in pure form or as a hemihydrate are also presented. The combination of e-urea with other organic solvents or the use of co-ligands have been shown to modulate its tendency to act as a bridging ligand, while fully N-alkylated urea derivatives represent appealing solvents. They have low melting point or can even be liquid at room temperature, making them media of choice, prone to ligation to the metal center in a terminal fashion given the absence of hydrogen bonding donor, favoring removal towards activation. The structures of the materials reported under urothermal conditions are described as well as their properties and applications.

Crystallization of the antimicrobial compound furacin (nitrofurazone) from 96%, 50%, and 20% hydrogen peroxide (HP) led to three novel solvates C₆H₆N₄O₄·H₂O₂, C₆H₆N₄O₄·1.5(H₂O₂), and C₆H₆N₄O₄·3.5(H₂O₂), respectively. Surprisingly, solvatomorphs that were richer in hydrogen peroxide were obtained from more dilute H₂O₂ solutions. The stability of the compounds decreased with an increase in peroxide content. These compounds represent a rare example of solvatomorphism (peroxomorphism) among crystalline hydrogen peroxide adducts. The structures of all the adducts were determined using X-ray crystallography. All of them contain a 1 : 1 chelating supramolecular synthon with a strong and unusual bifurcated donor hydrogen bond HOOH⋯(O₂N, furane). Compound C₆H₆N₄O₄·3.5(H₂O₂) is the first example of a structure containing 2D hydrogen-bonded layers built exclusively from peroxide molecules. In its crystal, a concerted flip-flop proton disorder of HP molecules was observed for the first time.

AlN/amorphous Ga₂O₃ heterojunction photodetectors were fabricated to achieve solar-blind UV detection. The responsivity and detectivity of the photodetector on a native substrate are 150% and 21.8% higher than those on a heterogeneous substrate at a 20 V bias, reaching 8.31 A W⁻¹ and 3.24 × 10¹⁴ Jones, respectively. The built-in electric field enables self-powered UV detection without an external power supply. The addition of a nanocolumnar AlN structure significantly improved the performance of the photodetector, achieving a photo-to-dark current ratio and responsivity up to 2.11 × 10⁷ and 9.17 mA W⁻¹ at 0 V bias. The fabricated photodetector has demonstrated self-powered and high-sensitivity UV detection.

A post-synthetic modification was employed to incorporate lanthanide Eu³⁺ ions into carbazole-functionalized UiO-67 metal–organic frameworks, successfully fabricating an efficient dual-emission fluorescence probe. The Eu³⁺-doped composite manifests superior luminescent properties and remarkable fluorescence stability, attributable to the sensitization and reinforcement afforded by the parent framework. Notably, the ligand's capability to capture external light and sensitize Eu³⁺ emissions led to observing characteristic peaks at 435 nm for the intrinsic ligand and 591, 614, 651, and 701 nm for Eu³⁺. The introduction of dipicolinic acid (DPA) serves a dual role: it acts as an antenna to absorb photons and replaces the coordinated water molecules of Eu³⁺, thereby preventing fluorescence quenching by water's O–H vibrations. Additionally, establishing hydrogen bonding between DPA and the carbazole dicarboxylic acid (CDC) initiates an intermolecular charge transfer (ICT) process, enhancing the ligand's fluorescence. Besides, the addition of DPA concurrently enhances the fluorescence emissions of both the ligand and Eu³⁺, displaying an unusual dual-enhanced “turn-on” fluorescence mode with an impressively low detection limit of 0.538 μM, accompanied by discernible color changes visible to the naked eye. Utilizing Eu@UiO-67-CDC as a test paper facilitates rapid on-site detection of DPA, eliminating the need for complex instrumentation. Moreover, the Eu@UiO-67-CDC probe can quantify DPA in environmental matrices such as river and lake water, with better recovery rates, indicating its significant potential for practical applications.

A novel photocatalyst for the construction of tubular graphitic carbon nitride (g-C₃N₄)/nickel oxide (NiO) heterojunction on carbon cloth (CC) is reported. Using ZnO nanorods as sacrificial template, tubular g-C₃N₄ nanosheets with thickness of 20 nm were grown on carbon cloth by thermal condensation. Then, NiO nanosheets were grown on g-C₃N₄ tubes by electrodeposition and calcination. In the light of visible light, the removal rates of rhodamine B (RhB) by g-C₃N₄/NiO/CC and g-C₃N₄/CC photocatalysts were 98% and 32%, respectively, within 60 min. The experiment was repeated five times, we found no significant decrease in photocatalyst activity. CC supported photocatalysts have broad application prospects in the degradation of organic dyes.

Three dinuclear dysprosium complexes 1–3 with structural formulas [Dy₂(bptz)(tta)₆]·2CH₂Cl₂ (1), [Dy₂(H₂bmtz)(tta)₆] (2) and [Dy₂(H₂bmtz)(hfac)₆(H₂O)₂] (3) (bptz = 3,6-di(2-pyridyl)-1,2,4,5-tetrazine, H₂bmtz = 3,6-di(2-pyrimidyl)-1,4-dihydro-1,2,4,5-tetrazine, tta = 2-thenoyltrifluoroacetonate, hfac = hexafluoroacetylacetonate) were synthesized by the use of two tetrazine derivative ligands containing six and eight nitrogen atoms in combination with β-diketonate co-ligands, which are a good research platform to study the synergistic influence of the local coordination environment and magnetic interaction on magnetic relaxation. Complexes 1 and 2 possess the same peripheral co-ligands and nearly the same coordination environment (approaching an ideal triangular dodecahedron), but different multi-nitrogen bridges involving N6 (bptz) and N8 (H₂bmtz) tetrazine derivatives. The structural difference leads to distinct magnetic relaxation properties with a hysteresis temperature of 2.5 K and 5.5 K at a rate of 200 Oe s⁻¹ in 1 and 2, respectively, which is most likely due to the different magnetic coupling transmitted by H₂bmtz and bptz in the direction close to the vertical magneto axis. Combined with a suitable local coordination environment, the energy barrier of complex 2 bridged by H₂bmtz can reach three times that of complex 3. Considering the local ligand field, the important influence of this multi-nitrogen bridge transmitting magnetic coupling on the SMM properties is demonstrated with the aid of ab initio calculations. Also of note is that complexes 2 and 3 are the first reported lanthanide SMMs constructed from dihydro-tetrazine.

Expression of concern for ‘Designing novel morphologies of L-cysteine surface capped 2D covellite (CuS) nanoplates to study the effect of CuS morphologies on dye degradation rate under visible light’ by Shahid Iqbal et al., CrystEngComm, 2020, 22, 4162–4173, https://doi.org/10.1039/D0CE00421A.

Coordination compounds with slow magnetic relaxation are of great interest due to their magnetic bistability. Herein, three cobalt(II) coordination polymers, formulated as {[Co₂(btca)(bpym)]·4H₂O}_n (1) and {[Co₂(btca)(bpym)]·2DMF·2H₂O}_n (2), {[Co₂(H₂btca)₂(bpym)]}_n (3) (H₄btca = 1,2,4,5-benzenetetracarboxylic acid; bpym = 2,2′-bipyrimidine), were solvothermally synthesized and magnetically characterized. Single-crystal structural analyses reveal that compounds 1 and 2 are Co²⁺ dimer-based one-dimensional (1D) and 2D coordination polymers, respectively, while compound 3 is a Co²⁺ chain-based 2D coordination polymer with a new topology. The Co²⁺ dimers and chains in these compounds are well magnetically isolated due to the bulk tetracarboxylic linker. Magnetic studies reveal that antiferromagnetic interactions exist between the Co²⁺ ions bridged by the bpym ligand. For 1, no relaxation behavior can be detected, suggesting the paramagnetic behavior of 1. Interestingly, alternating current (AC) magnetic measurements observed slow magnetic relaxation under a 1000 Oe field for 2 and 3. These results provide not only three cobalt(II) coordination polymers with varying topology and magnetic behaviors but also a pyrimidine–tetracarboxylic ligand platform for designing new slow magnetic relaxing coordination polymers.

A novel and green microfluidic approach was employed for the synthesis of undoped and Eu(III)-doped calcium molybdate at room and low temperatures. The controlled formation of nano- and microstructures was successfully achieved by tuning the nucleation and growth stages of particle formation through a systematic variation of the viscosity and dielectric constant of the reaction medium, i.e. water and ethanol in different weight ratios and at different temperatures. Thanks to the inherent advantages of the microfluidic approach in terms of mass transport, mixing and heat exchange, it was possible to carry out the reaction at low temperature (−4 °C) in an effective manner and to further control the reaction conditions to achieve the formation of small and monodisperse nanoparticles. The synthesised nano- and microstructures, displaying different morphologies depending on reaction conditions, were investigated from a structural (XRD), dimensional and morphological (TEM, SEM), compositional (ICP-MS), and functional (photoluminescence) point of view. The remarkable photoluminescence properties of pure and Eu(III)-doped calcium molybdate structures proved that they are promising materials to be employed as phosphors.