Recent Trends and Advances in Porous Metal-Organic Framework Nanostructures for the Electrochemical and Optical Sensing of Heavy Metals in Water

With the expansion and advancement in agricultural and chemical industries, various toxic heavy metals such as lead, cadmium, mercury, zinc, copper, arsenic etc. are continuously released into the environment. Intake of sources contaminated with such toxic metals leads to various health issues. Keeping the serious effects of these toxic metal ions in view, various organic-inorganic nanomaterials based sensors have been exploited for their detection via optical, electrochemical and colorimetric approaches. Since a chemical sensor works on the principle of interaction between the sensing layer and the analytes, a sensor material with large surface area is required to enable the largest possible interaction with the target molecules and hence the sensitivity of the chemical sensor. However, commonly employed materials such as metal oxides and conducting polymers tend to feature relatively low surface areas, and hence resulting in low sensitivity of the sensor. Metal-Organic Frameworks (MOFs) nanostructures are another category of organic-inorganic materials endowed with large surface area, ultra-high and tunable porosity, post-synthesis modification features, readily available active sites, catalytic activity, and chemical/thermal stability. These properties provide high sensitivity to the MOF based sensors due to the adsorption of large number of target analytes. The current review article focuses on MOFs based optical and electrochemical sensors for the detection of heavy metals.

Rare-earth metal–organic frameworks: from structure to applications

In the past 30 years, rare-earth metal–organic frameworks (MOFs) have been gaining attention owing to their diverse chemical structures, and tunable properties.

Sensing organic analytes by metal–organic frameworks: a new way of considering the topic

In this review, our goal is comparison of advantageous and disadvantageous of MOFs about signal-transduction in different instrumental methods for detection of different categories of organic analytes.

Accordion-Like Motion in Electrochemically Switchable Crown Ether/Ammonium Oligorotaxanes

Reversible oxidation reactions in electrochemically switchable oligorotaxanes with tetrathiafulvalene (TTF) decorated 24-crown-8 ether wheels generate intramolecular mixed-valence and radical-cation interactions between the wheels. This induces shuttling of the wheels and a contraction of inter-wheel distances. Further oxidation generates repulsive forces between the TTFs and maximizes the inter-wheel distances instead. These interactions and co-conformational changes were not observed for structurally similar controls in which acetyl groups along the axle prevent translational motion of the wheels. This operation mode of oligorotaxanes, which is reminiscent of an accordion-like motion, is promising for functional materials and nanodevices such as piston-type rotaxane motors.

A multifunctional Eu-CP as a recyclable luminescent probe for the highly sensitive detection of Fe3+/Fe2+, Cr2O72−, and nitroaromatic explosives

A multifunctional Eu-CP (1) as a recyclable luminescent probe for the highly sensitive detection of Fe³⁺/Fe²⁺, Cr₂O₇²⁻, and nitroaromatic explosives.

A bi-metallic MOF catalyst via sensitive detection & adsorption of Fe3+ ions for size-selective reaction prompting

Novel MOF adsorbed Fe³⁺ presents the first example of a bi-metallic Lewis-acid catalyst for the cyanosilylation reaction in a size-selective fashion.

A bifunctional luminescent europium–organic framework for highly selective sensing of nitrobenzene and 4-aminophenol

A bifunctional luminescent Eu-MOF can be applied as a highly selective and sensitive bifunctional luminescence sensor to detect NB and 4-AP through an energy competition mechanism with low detection limits of 5–70 ppm and 5–110 ppm, respectively.

Anionic metal–organic framework for high-efficiency pollutant removal and selective sensing of Fe(iii) ions

An anionic metal–organic framework, (DMA)₂[Y₉(μ₃-OH)₈(μ₂-OH)₃BTB₆]_n·(solv)_x, (gea-MOF-1), is a novel rare earth (RE) nonanuclear MOF with an unusual gea topology that can be used as an adsorbent material for efficient removal of cationic dye MB⁺.

A luminescent metal–organic framework for highly selective sensing of nitrobenzene and aniline

A luminescent metal–organic frameworkgea-MOF-1, can act as a fluorescent sensor for sensitive and selective detection of nitrobenzene and aniline. More importantly, the detection limit of nitrobenzene is on the 5–60 ppm scale.

Lanthanide-based metal–organic frameworks as luminescent probes

We discuss the construction of lanthanide-based metal–organic frameworks, their applications in possible detection mechanisms, and summarize some examples of Ln-MOFs as luminescent probes.