Schiff base MOFs and their derivatives for sequestration and degradation of pollutants: present and future

Removal of contaminants via adsorption and catalysis have received a significant interest as energy and money-saving solutions for treating the world's wastewater. Metal-organic frameworks (MOFs), a newly discovered class of porous crystalline materials, have demonstrated tremendous promise in the removal and destruction of contaminants for water purification. In order to improve the interactions of MOFs with the target pollutants for their selective removal and degradation, the Schiff base functionalities emerged as promising active sites. Through pre- and post-synthetic alterations, Schiff base functionalities are integrated into the pore cages of MOF adsorbent materials. To understand the adsorptive/catalytic mechanism, potential interactions between the Schiff base sites and the target pollutants are discussed. Based on cutting-edge techniques for their synthesis, this paper examines current developments in the creation of Schiff base-functionalized MOFs as innovative materials for adsorptive removal and catalytic degradation of contaminants for water remediation.

Recent Progress in the Development of MOF-Based Photocatalysts for the Photoreduction of Cr(VI)

There has been a direct correlation between the rate of industrial development and the spread of pollution on Earth, particularly in the last century. The organic and inorganic pollutants generated from industrial activities have created serious risks to human life and the environment. The concept of sustainability has emerged to tackle the environmental issues in developing chemical-based industries. However, pollutants have continued to be discharged to water resources, and finding appropriate techniques for the removal and remedy of wastewater is in high demand. Chromium is one of the high-risk heavy metals in industrial wastewaters that should be removed via physical adsorption and/or transformed into less hazardous chemicals. Photocatalysis as a sustainable process has received considerable attention as it utilizes sunlight irradiation to remedy Cr^(VI) via a cost-effective process. Numerous photocatalytic systems have been developed up to now, but metal-organic frameworks (MOFs) have gained growing attention because of their unique versatilities and facile structural modulations. A variety of MOF-based photocatalysts have been widely employed for the photoreduction of Cr^(VI). Here, we review the recent progress in the design of MOF photocatalysts and summarize their performance in photoreduction reactions.

Heterometallic Dual-Liganded AE-Ln-CPs Luminescent Probes for Efficient Sensing of Fe(III) Ions

Iron ion is widely present in the environment and in biological systems, and are indispensable trace elements in living organisms, so development of an efficient and simple sensor for sensing Fe(III) ions has attracted much attention. Here, six heterometallic AE-Ln coordination polymers (CPs) [Ln₂ (pda)₄(Hnda)₂Ca₂(H₂O)₂]·MeOH (Ln = Eu (1), Tb (2); H₂pda = 2,6-pyridinedicarboxylic acid, H₂nda = 2,3-naphthalenedicarboxylic acid), [Ln (pda)₂ (nda)AE₂(HCOO)(H₂O)] (AE = Sr, Ln = Eu (3), Tb (4); AE = Ba, Ln = Eu (5), Tb (6)) with two-dimensional (2D) layer structures were synthesized by hydrothermal method. All of them were characterized by elemental analysis, XRD, IR, TG, as well as single crystal X-ray diffraction. They all show infinite 2D network structure, where complexes 1 and 2 are triclinic with space group of P1¯, while 3-6 belong to the monoclinic system, space group P2_1/n. The solid-state fluorescence lifetimes of complexes 1, 3 and 5 are τ_obs1 = 1930.94, 2049.48 and 2,413.04 µs, respectively, and the quantum yields Ф_total are 63.01, 60.61, 87.39%, respectively, which are higher than those of complexes 2, 4 and 6. Complexes 1-6 all exhibited efficient fluorescence quenching response to Fe³⁺ ions in water, and were not interfered by the following metal ions: Cu²⁺, Cd²⁺, Mg²⁺, Ni²⁺, Co²⁺, Ca²⁺, Ba²⁺, Sr²⁺, Li⁺, Na⁺, K⁺, Al³⁺, Fe²⁺, Pb²⁺, Cr³⁺, Mn²⁺ and Zn²⁺. The quenching coefficient K_SV for complexes 1-6 is 1.41 × 10⁵ M⁻¹, 7.10 × 10⁴ M⁻¹, 1.70 × 10⁵ M⁻¹, 1.57 × 10⁵ M⁻¹, 9.37 × 10⁴ M⁻¹, 1.27 × 10⁵ M⁻¹, respectively. The fluorescence quenching mechanism of these complexes towards Fe³⁺ ions was also investigated. It is possible that the weak interaction formed between the complexes and the Fe³⁺ ions reduce the energy transfer from the ligand to the Ln³⁺ ion, producing the emission burst effect. This suggests that complexes 1-6 can be candidate for efficient luminescent sensor of Fe³⁺.

Regulating the proton conductivity of metal organic framework materials through solvent control

MOFs were used as probes through changes in the proton conductivity caused by changes in solvent molecules.

Nanoscale Metal-Organic Frameworks: Recent developments in synthesis, modifications and bioimaging applications

Porous Metal-Organic Frameworks (MOFs) have emerged as eye-catching materials in recent years. They are widely used in numerous fields of chemistry thanks to their desirable properties. MOFs have a key role in the development of bioimaging platforms that are hopefully expected to effectually pave the way for accurate and selective detection and diagnosis of abnormalities. Recently, many types of MOFs have been employed for detection of RNA, DNA, enzyme activity and small-biomolecules, as well as for magnetic resonance imaging (MRI) and computed tomography (CT), which are valuable methods for clinical analysis. The optimal performance of the MOF in the bio-imaging field depends on the core structure, synthesis method and modifications processes. In this review, we have attempted to present crucial parameters for designing and achieving an efficient MOF as bioimaging platforms, and provide a roadmap for researchers in this field. Moreover, the influence of modifications/fractionalizations on MOFs performance has been thoroughly discussed and challenging problems have been extensively addressed. Consideration is mainly focused on the principal concepts and applications that have been achieved to modify and synthesize advanced MOFs for future applications.

1D ladder and 2D bilayer coordination polymers constructed from a new T-shaped ligand: luminescence, magnetic and CO2 gas adsorption properties

1D ladder and 2D bilayer coordination polymers are constructed by using a new T-shaped ligand, in which the 2D bilayer exhibits CO₂ gas adsorption features.

Three water-stable luminescent two-dimensional CdII-based coordination polymers as sensors for highly sensitive and selective detection of Cr2O72− and CrO42− anions

Three 2D Cd^II-CPs with different topologies were prepared, in which 1 and 3 are rare examples which display excellent sensitivity, selectivity, recyclability and structural stabilities for the detection of Cr₂O₇²⁻/CrO₄²⁻.

A new Zn(ii)-based 3D metal–organic framework with uncommon sev topology and its photocatalytic properties for the degradation of organic dyes

A new Zn(ii) based 3D MOF having uncommon sev topology synthesized and used as efficient photocatalyst for the photodegradation of dyes methyl violet and rhodamine B.

Luminescence sensing, electrochemical, and magenetic properties of 2D coordination polymers based on the mixed ligands p-terphenyl-2,2′′,5′′,5′′′-tetracarboxylate acid and 1,10-phenanthroline

Four 2D CPs were constructed and provided platforms to investigate the electrochemical behavior, luminescence sensing of Cr(vi) and pesticides, and magnetic properties.

Structural diversity, magnetic properties, and luminescence sensing of five 3D coordination polymers derived from designed 3,5-di(2′,4′-dicarboxylphenyl)benozoic acid

Five 3D CPs were constructed from a designed π-conjugated aromatic pentacarboxylate with diverse structures.