Water-Stable Homochiral Cluster Organic Frameworks Built by Two Kinds of Large Tetrahedral Cluster Units

Two histidine-templated metal phosphate-oxalates: solvent-free synthesis, luminescence, and proton-conducting properties

Two new histidine-templated metal phosphate-oxalates (MPOs) were prepared under solvent-free conditions. Single-crystal X-ray diffraction analysis reveals that they have layered and chainlike structures, respectively. Under ultraviolet light irradiation, the two MPOs exhibit blue luminescence originating from histidine templates. Their proton-conducting properties were also investigated under different conditions.

Recent Advances in MOF-Based Adsorbents for Dye Removal from the Aquatic Environment

The adsorptive removal of dyes from industrial wastewater using commercially available adsorbents is not significantly efficient. Metal–organic frameworks (MOFs) offer outstanding properties which can boost the separation performance over current commercial adsorbents and hence, these materials represent a milestone in improving treatment methods for dye removal from water. Accordingly, in this paper, the recent studies in the modification of MOF structures in dye removal from the aquatic environment have been discussed. This study aims to elaborate on the synthetic strategies applied to improve the adsorption efficiency and to discuss the major adsorption mechanisms as well as the most influential parameters in the adsorptive removal of dyes using MOFs. More particularly, the advanced separation performance of MOF-based adsorbents will be comprehensively explained. The introduction of various functional groups and nanomaterials, such as amine functional groups, magnetic nanoparticles, and carbon-based materials such as graphene oxide and CNT, onto the MOFs can alter the removal efficiency of MOF-based adsorbents through enhancing the water stability, dispersion in water, interactions between the MOF structure and the contaminant, and the adsorption capacity. Finally, we summarize the challenges experienced by MOF-based materials for dye removal from water and propose future research outlooks to be considered.

Luminescent cluster-organic frameworks constructed from predesigned supertetrahedral {Ln4Zn6} secondary building units

3d-4f heterometallic supertetrahedral clusters with the formula of Ln₄Zn₆(μ₆-O)L₄(CH₃COO)₆(NO₃)₄(CH₃OH)₄(H₂O)₂ (1-Ln, Ln = Eu, Gd, Tb, H₃L = 2-(hydroxymethyl)-2-(pyridin-4-yl)-1,3-propanediol) have been successfully introduced as stable secondary building units (SBUs) to construct new cluster-organic frameworks with tunable emission, demonstrating a promising strategy for developing new optical materials.

Construction of high-nuclear 4p–4f heterometallic {Ln11Ge12} cluster-organic frameworks with high-sensitivity luminescence sensing of Fe3+ in aqueous solution

The [Pr₁₁Ge₁₂] 4p–4f cluster-organic framework shows highly selective and sensitive sensing of Fe³⁺ in aqueous solution.

Cluster–oxalate frameworks with extra-large channels: solvent-free synthesis, chemical stability, and proton conduction

Two cluster–oxalate frameworks (denoted as SCU-62 and SCU-65) were prepared under solvent-free conditions.

Incorporating polyoxometalates and organic ligands to pursue 3d–4f heterometallic clusters: a series of {Cr4Ln4} clusters stabilized by phthalic acid and [SiW12O40]4−

By introduction of trilacunary Keggin-type polyoxometalate to the hydrothermal reaction system of Cr³⁺, Ln³⁺ and phthalic acid, a series of novel {Cr₄Ln₄} heterometallic clusters with the formula Cs₂[Cr₄Ln₄(μ₄-O)₄(μ₃-O)₄(C₈H₄O₄)₄(H₂O)₁₂](H₃SiW₁₂O₄₀)Cl·23H₂O (1-Ln, Ln = Ce, Pr, Nd) and [Cr₄Ln₄(μ₄-O)₄(μ₃-O)₄(C₈H₄O₄)₄(H₂O)₁₀](H₆SiW₁₂O₄₀)Cl₂·18H₂O (2-Ln, Ln = Sm, Eu, Gd, Tb, Dy, Ho, Er) have been obtained. Single-crystal structural analyses show that 1-Ln and 2-Ln constitute the first cases of Cr–Ln heterometallic clusters stabilized by inorganic polyoxometalate anions and organic ligands. Optical spectra studies demonstrate that 1-Ln and 2-Ln are narrow-gap semiconductors with band gaps of about 1.5 eV. Magnetic investigation shows that compound 2-Dy is a potential single molecule magnet.

By introduction of trilacunary Keggin-type polyoxometalate to the hydrothermal reaction system of Cr³⁺, Ln³⁺ and phthalic acid, a series of novel {Cr₄Ln₄} heterometallic clusters have been obtained.

Induced Aggregation and Synergistic Coordination Strategy in Cluster Organic Architectures

Developments in strategies for the synthesis of oxo-hydroxo lanthanide (Ln) clusters during the past few decades have resulted in abundant relevant crystalline materials that exhibit attractive structures and interesting properties. The combination of these oxo-hydroxo Ln clusters and organic ligands has led to the formation of new extended arrays of Ln cluster organic frameworks (LnCOFs). In contrast to metal-organic frameworks, the incorporation of particular characteristics of clusters provides the opportunity to develop performances not available in single-metal compounds. Even with steady advances in oxo-hydroxo Ln clusters, progress in LnCOFs is less developed. To obtain LnCOFs, one premise is to induce the oxophilic Ln ions undergoing aggregation. Meanwhile, the organic ligands should have extra coordination sites for further expansion. Multidentate organic ligands like pyrazinecarboxylic acid and pyridinecarboxylic acid containing O and N donors will meet these two requirements. Their carboxyl groups will induce the aggregation of Ln ions, while the N donors can serve as potential extension sites. To make more open frameworks or if the oxo-hydroxo Ln clusters fail to be congregated or connected, then a second ligand is necessary. The introduction of the suitable second ligand may occupy a partial coordination sphere of Ln ions and ultimately benefit the connection process. In this Account, we introduce the origin and evolution of the induced aggregation and synergistic coordination strategy. According to the attributes of the organic ligands in the documented LnCOFs, we classify them into linear and nonlinear groups in the second and third parts. From the aspect of ligand-induced aggregation, isonicotinic acid (HIN) and lengthened 4-(4-pyridyl)benzoic acid (HPBA) ligands as well as their nonlinear analogues are settled as typical models. From the aspect of synergistic coordination, chelating ligands like 1,2-benzenedicarboxylic acid (1,2-H₂BDC) and acetic acid (HOAc) play significant roles. Moreover, three types of synergistic coordination are discussed in detail: synergistic coordination between two types of organic ligands, synergistic coordination between organic and inorganic ligands, and simultaneous synergistic coordination of aforementioned two types. From the aspect of LnCOF products, in addition to traditional pure LnCOFs, new types of heterometallic frameworks containing two types of cluster building units have been developed. Although this Account focuses on the nuclearity and coordination aspects of LnCOFs, we anticipate that it will stimulate more efforts in the further study of their properties beyond the exploratory synthesis. More importantly, synergistic coordination may be applied to other systems and inspire crystal design and targeted assembly of new functional materials.

Composite cluster-organic frameworks based on polyoxometalates and copper/cobalt–oxygen clusters

The first two cluster organic frameworks based on Anderson-type polyoxometalates and copper/cobalt-oxo cluster secondary building units have been successfully made under solvothermal conditions.

Water stable oxalate-based coordination polymers with in situ generated cyclic dipeptides showing high proton conductivity

Presented here are two water stable oxalate-based coordination polymers with in situ generated cyclic dipeptides, which show high proton conductivities on the order of 10⁻³ S cm⁻¹ at 85 °C under 98% relative humidity.

Three Cluster Organic Frameworks Constructed from Tetranuclear Cluster Units: Structure and Properties

By treating a semirigid 5-oxyacetate isophthalic acid (H₃ OAIP) ligand with MnSO₄ /CoSO₄ /CdSO₄ under solvothermal conditions, three isostructural cluster organic frameworks, [M₂ (OH)(OAIP)(DMA)]⋅H₂ O (M=Mn²⁺ (1), Co²⁺ (2), Cd²⁺ (3); DMA=N,N'-dimethylacetamide) were constructed. The three complexes contain novel eight-connected tetranuclear M₄ (OH)₂ (COO)₆ (OCH₂ COO)₂ clusters with the unique hexagonal bipyramidal configuration, which are extended by four-connected OAIP linkers to form an uncommon (4,8)-connected alb-4,8-Cmce topology based on (3,6)-connected kgd sublayers. Both 1 and 2 showed significant antiferromagnetic interactions between the intracluster metal ions, whereas 3 revealed strong blue photoluminescence.