Photoactive metal-organic framework as a bifunctional material for 4-hydroxy-4'-nitrobiphenyl detection and photodegradation of methylene blue

A review of metal-organic framework (MOF) materials as an effective photocatalyst for degradation of organic pollutants

Water plays a vital role in all aspects of life. Recently, water pollution has increased exponentially due to various organic and inorganic pollutants. Organic pollutants are hard to degrade; therefore, cost-effective and sustainable approaches are needed to degrade these pollutants. Organic dyes are the major source of organic pollutants from coloring industries. The photoactive metal-organic frameworks (MOFs) offer an ultimate strategy for constructing photocatalysts to degrade pollutants present in wastewater. Therefore, tuning the metal ions/clusters and organic ligands for the better photocatalytic activity of MOFs is a tremendous approach for wastewater treatment. This review comprehensively reports various MOFs and their composites, especially POM-based MOF composites, for the enhanced photocatalytic degradation of organic pollutants in the aqueous phase. A brief discussion on various theoretical aspects such as density functional theory (DFT) and machine learning (ML) related to MOF and MOF composite-based photocatalysts has been presented. Thus, this article may eventually pave the way for applying different structural features to modulate novel porous materials for enhanced photodegradation properties toward organic pollutants.

Recent Development on Sensing Strategies for Small Molecules Detections

Sensors play a critical role in the detection and monitoring of various substances present in our environment, providing us with valuable information about the world around us. Within the field of sensor development, one area that holds particular importance is the detection of small molecules. Small molecules encompass a wide range of organic or inorganic compounds with low molecular weight, typically below 900 Daltons including gases, volatile organic compounds, solvents, pesticides, drugs, biomarkers, toxins, and pollutants. The accurate and efficient detection of these small molecules has attracted significant interest from the scientific community due to its relevance in diverse fields such as environmental pollutants monitoring, medical diagnostics, industrial optimization, healthcare remedies, food safety, ecosystems, and aquatic and terrestrial life preservation. To meet the demand for precise and efficient monitoring of small molecules, this summary aims to provide an overview of recent advancements in sensing and quantification strategies for various organic small molecules including Hydrazine, Glucose, Morpholine, Ethanol amine, Nitrosamine, Oxygen, Nitro-aromatics, Phospholipids, Carbohydrates, Antibiotics, Pesticides, Drugs, Adenosine Triphosphate, Aromatic Amine, Glutathione, Hydrogen Peroxide, Acetone, Methyl Parathion, and Thiophenol. The focus is on understanding the receptor sensing mechanism, along with the electrical, optical, and electrochemical response. Additionally, the variations in UV-visible spectral properties of the ligands upon treatment with the receptor, fluorescence and absorption titration analysis for limit of detection (LOD) determination, and bioimaging analysis are discussed wherever applicable. It is anticipated that the information gathered from this literature survey will be helpful for the perusal of innovation regarding sensing strategies.

Selective detection of sulfasalazine antibiotic and its controllable photodegradation into 5-aminosalicylic acid by visible-light-responsive metal-organic framework

The extensive use of sulfasalazine (SSZ) antibiotics has brought potential threats to aquatic ecosystems and human health. Thus, necessary measures for the removal of SSZ must be taken to prevent arbitrary antibiotic exposure to the aquatic environment. However, not all the recent photocatalysts that have been used for the degradation of SSZ could not achieve the controlled release of SSZ and hence are losing their medicinal values. Herein, by utilizing an Eosin Y moiety as an efficient light-harvesting and emission site, an Eosin Y-based visible-light-responsive metal-organic framework has been synthesized and characterized, which exhibits high selectivity for detecting the antibiotic SSZ in water and simulated physiological conditions, with a detection limit of below 1 μM (0.4 μg mL^-1). It also represents the first example of a MOF-based photocatalyst for the controllable degradation of SSZ into 5-aminosalicylic acid with excellent catalytic activity and recyclability.

Synthesis, Structure, and Photocatalytic Activity of TiO2-Montmorillonite Composites

In the present study, TiO2-montmorillonite (MMT) composites were synthesized hydrothermally under variable conditions, including the TiO2/MMT mass ratio, reaction pH, reaction temperature, and dwelling time. These samples were determined by X-ray photoelectron spectrometry (XPS), ultraviolet–visible spectroscopy% (UV-Vis DRS), electrochemical impedance spectroscopy (EIS), transient photocurrent responses, photoluminescence (PL) spectra, electron paramagnetic resonance (EPR), and N2 adsorption–desorption isotherms. The photocatalytic activity was evaluated as the ability to promote the visible-light-driven degradation of 30 mg/L of aqueous methylene blue, which was maximized for the composite with a TiO2 mass ratio of 30 wt% prepared at a pH of 6, a reaction temperature of 160 °C, and a dwelling time of 24 h (denoted as 30%-TM), which achieved a methylene blue removal efficiency of 95.6%, which was 4.9 times higher than that of pure TiO2. The unit cell volume and crystallite size of 30%-TM were 92.43 Å3 and 9.28 nm, respectively, with a relatively uniform distribution of TiO2 particles on the MMT’s surface. In addition, 30%-TM had a large specific surface area, a strong light absorption capacity, and a high Ti3+ content among the studied catalysts. Thus, the present study provides a basis for the synthesis of composites with controlled structures.

1,3-Bis(4′-carboxylatophenoxy)benzene and 3,5-bis(1-imidazoly)pyridine derived Zn(ii)/Cd(ii) coordination polymers: synthesis, structure and photocatalytic properties

Zn(ii) and Cd(ii)-based CPs derived from a 1,3-bis(4′-carboxylatophenoxy)benzene and 3,5-bis(1-imidazoly)pyridine synthesized and their photocatalytic properties for decomposition of methylene blue investigated.

Metal–organic frameworks derived from a semi-rigid anthracene-based ligand and sulfonates: proton conductivity and dye degradation studies

The MOFs were constructed by ligand AHP and sulfonate analogues. MOF4 exhibits a high proton conductivity of 1.95 × 10⁻³ S cm⁻¹ at 95 °C and 98% relative humidity. MOFs 1–5 also serve as photocatalysts for methylene blue degradation.

Luminescent triphenylamine-based metal-organic frameworks: recent advances in nitroaromatics detection

Luminescent metal-organic frameworks (LMOFs), as one branch of MOFs, have attracted considerable attention in recent years due to their good crystallinity, structural diversity, tunable porosity and easily induced fluorescence emission. Importantly, their photoluminescence (PL) properties can be adjusted by altering metal ions or metal clusters and organic ligands in one hybrid system. Among the various sensing applications, using LMOFs as chemical sensors to detect the explosive and environment pollution causing nitroaromatic compounds (NACs) is an important topic. In this account, we describe the recent advancements in the field of NAC detection by LMOFs based on the triphenylamine (TPA) unit as the π-conjugated fluorophore.

Coordination Polymers Based on Highly Emissive Ligands: Synthesis and Functional Properties

Coordination polymers are constructed from metal ions and bridging ligands, linking them into solid-state structures extending in one (1D), two (2D) or three dimensions (3D). Two- and three-dimensional coordination polymers with potential voids are often referred to as metal-organic frameworks (MOFs) or porous coordination polymers. Luminescence is an important property of coordination polymers, often playing a key role in their applications. Photophysical properties of the coordination polymers can be associated with intraligand, metal-centered, guest-centered, metal-to-ligand and ligand-to-metal electron transitions. In recent years, a rapid growth of publications devoted to luminescent or fluorescent coordination polymers can be observed. In this review the use of fluorescent ligands, namely, 4,4'-stilbenedicarboxylic acid, 1,3,4-oxadiazole, thiazole, 2,1,3-benzothiadiazole, terpyridine and carbazole derivatives, naphthalene diimides, 4,4',4''-nitrilotribenzoic acid, ruthenium(II) and iridium(III) complexes, boron-dipyrromethene (BODIPY) derivatives, porphyrins, for the construction of coordination polymers are surveyed. Applications of such coordination polymers based on their photophysical properties will be discussed. The review covers the literature published before April 2020.

Synthesis, structure and photocatalytic properties of coordination polymers based on pyrazole carboxylic acid ligands

The photocatalytic activities of two novel different 2-D coordination polymers constructed from 5-hydroxy-1H-pyrazole-3-carboxylic acid ligand have been explored.

Trifunctional metal–organic platform for environmental remediation: structural features with peripheral hydroxyl groups facilitate adsorption, degradation and reduction processes

A Cd(ii)-based metal–organic framework (MOF) has been demonstrated to have trifunctional properties, namely as an efficient and selective adsorbent for dyes, a visible-light-active photocatalyst for the degradation of dyes and a photocatalyst for Cr(vi) reduction.