A novel hybrid lanthanide metal-organic frameworks based on porphyrin for rapid detection of iron ions

BACKGROUND

Iron ion (Fe3+) is essential for the environment and human health. Detecting Fe3+ in water is crucial, making high-performance detection a key objective. Lanthanide metal-organic frameworks with abundant functional sites have been deemed a promising fluorescence sensor for Fe3+ detection. Currently, most metal-organic framework-based sensors for Fe3+ detection have cumbersome and time-consuming synthesis procedures and long detection times, which greatly limits their practical application. This study aims to construct a hybrid lanthanide metal-organic frameworks-based fluorescence sensor for Fe3+ detection that promises simple and rapid iron ion quantification in water.

RESULTS

A novel hybrid lanthanide metal-organic frameworks (ECTMNs) was synthesized in one step using a solvothermal method with only 4 h. The frameworks comprise two metal ions, cerium and europium, serving as metal centers, and 4,4,4,4-(Porphine-5,10,15,20-tetrayl) tetrakis (TCPP) as an organic ligand. With the addition of Fe3+, the host-guest reaction occurred between Fe3+ and ECTMNs probe, leading to the gradual fluorescence burst of ECTMNs probe. A strong linear correlation between ECTMNs fluorescence intensity and Fe3+ concentration (1-90 μM) makes it a reliable sensor for Fe3+ monitoring with a detection limit of 0.3 μM. Moreover, the method was used to analyze real samples (tap water and river water), showing good recoveries (92-98 %) and low relative standard deviations (3.96-6.11 %), making it a promising option for rapidly detecting Fe3+.

SIGNIFICANCE AND NOVELTY

A rapid synthesis protocol for hybrid lanthanide metal-organic frameworks is proposed in this study. The obtained ECTMNs exhibits good water solubility, high stability, and specificity for Fe3+. Based on ECTMNs, an innovative fluorescence sensor is established for selectively detecting Fe3+ in water, which is a simple operation method with a low detection limit and short sensing time. It provides a novel method for accurately and rapidly detecting Fe3+ in environmental pollution and water safety monitoring.

A Ratiometric Fluorescent Probe Based on RhB Functionalized Tb-MOFs for the Continuous Visual Detection of Fe3+ and AA

In this study, a red-green dual-emitting fluorescent composite (RhB@MOFs) was constructed by introducing the red-emitting organic fluorescent dye rhodamine B (RhB) into metal-organic frameworks (Tb-MOFs). The sample can be used as a ratiometric fluorescent probe, which not only avoids errors caused by instrument and environmental instability but also has multiple applications in detection. The results indicated that the RhB@MOFs exhibited a turned-off response toward Fe3+ and a turned-on response for the continuous detection of ascorbic acid (AA). This ratiometric fluorescent probe possessed high sensitivity and excellent selectivity in the continuous determination of Fe3+ and AA. It is worth mentioning that remarkable fluorescence change could be clearly observed by the naked eye under a UV lamp, which is more convenient in applications. In addition, the mechanisms of Fe3+- and AA-induced fluorescence quench and recovery are discussed in detail. This ratiometric probe displayed outstanding recognition of heavy metal ions and biomolecules, providing potential applications for water quality monitoring and biomolecule determination.

A Ni(II) Metal-Organic Framework with Mixed Carboxylate and Bipyridine Ligands for Ultrafast and Selective Sensing of Explosives and Photoelectrochemical Hydrogen Evolution

We report a Ni-MOF (nickel metal-organic framework), Ni-SIP-BPY, synthesized by using two linkers 5-sulfoisophthalic acid (SIP) and 4,4'-bipyridine (BPY) simultaneously. It displays an orthorhombic crystal system with the Ama2 space group: a = 31.425 Å, b = 19.524 Å, c = 11.2074 Å, α = 90°, β = 90°, γ = 90°, and two different types of nickel(II) centers. Interestingly, Ni-SIP-BPY exhibits excellent sensitivity (limit of detection, 87 ppb) and selectivity toward the 2,4,6-trinitrophenol (TNP)-like mutagenic environmental toxin in the pool of its other congeners via "turn-off" fluorescence response by the synergism of resonance energy transfer, photoinduced electron transfer, intermolecular charge transfer, π-π interactions, and competitive absorption processes. Experimental studies along with corroborated theoretical experimentation, vide density functional theory studies, shed light on determining the plausible mechanistic pathway in selective TNP detection, which is highly beneficial in the context of homeland security perspective. Along with the sensing of nitroaromatic explosives, the moderately low band gap and the p-type semiconducting behavior of Ni-SIP-BPY make it suitable as a photoanode material for visible-light-driven water splitting. Highly active surface functionalities and sufficient conduction band minima effectively reduce the water and result in a seven times higher photocurrent density under visible-light illumination.

Metal-Organic Frameworks for Liquid Phase Applications

In the last two decades, metal-organic frameworks (MOFs) have attracted overwhelming attention. With readily tunable structures and functionalities, MOFs offer an unprecedentedly vast degree of design flexibility from enormous number of inorganic and organic building blocks or via postsynthetic modification to produce functional nanoporous materials. A large extent of experimental and computational studies of MOFs have been focused on gas phase applications, particularly the storage of low-carbon footprint energy carriers and the separation of CO2-containing gas mixtures. With progressive success in the synthesis of water- and solvent-resistant MOFs over the past several years, the increasingly active exploration of MOFs has been witnessed for widespread liquid phase applications such as liquid fuel purification, aromatics separation, water treatment, solvent recovery, chemical sensing, chiral separation, drug delivery, biomolecule encapsulation and separation. At this juncture, the recent experimental and computational studies are summarized herein for these multifaceted liquid phase applications to demonstrate the rapid advance in this burgeoning field. The challenges and opportunities moving from laboratory scale towards practical applications are discussed.

Efficient luminescence sensing in two lanthanide metal–organic frameworks with rich uncoordinated Lewis basic sites

Two novel Ln-MOFs containing uncoordinated Lewis basic sites for sensitive detection of Fe3+ ions and nitrobenzene through fluorescence quenching.

Zn(ii) and Cd(ii) coordination polymers with a new angular bis-pyridyl-bis-amide: synthesis, structures and sensing properties

Zn(ii) and Cd(ii) coordination polymers that show a 2D double layer with the rare (4⁶·6⁴)-5 L4 topology and a 3D framework with a new (4·5·6)(4⁵·5⁵·6⁹·7·8) topology, respectively, show good selectivity toward the detection of Fe³⁺ ions.

Two Co(ii)-based coordination polymers as multi-responsive luminescent sensors for the detection of levofloxacin, benzaldehyde and Fe3+ ions in water media

Two CPs display excellent sensitivity, selectivity and low limits of detection for detection of LEV, BZH and Fe3+ ions.

Selective sensing of Fe3+ ions in aqueous solution by a biodegradable platform based lanthanide metal organic framework

As a significant metal ion in the environmental and biological systems, excess or shortage of Fe³⁺ from the organism can cause a host of diseases. So it is very urgent to explore an explicit, rapid and recoverable method for the detection of Fe³⁺ ions. Herein, a novel and flexible ligand containing 12 carboxyl groups (BHM-COOH) is used for the structure of a series of luminescent Eu³⁺/Tb³⁺-metal-organic frameworks (MOFs). A reliable and convenient luminescent detection platform is constructed by combining polylactic acid (PLA) film with Eu_0.24Tb_0.76-BHM-COOH. More importantly, the luminescent platform can highly sensitive to sense Fe³⁺ ions through fluorescence quenching (Stern-volmer constant Ksv = 1.27 × 10⁴ M^-1 for Fe(NO₃)₃), and detection limit can be as low as 4.47 μM. The sensing mechanism is ascribed to the fluorescence quenching caused by the competitive absorption between Eu_0.24Tb_0.76-BHM-COOH and Fe³⁺ ion. At the same time, the sensor can be reused many times. These exciting results indicate that Eu_0.24Tb_0.76-BHM-COOH film can serve as a promising multi-responsive luminescent sensor for environmental pollutant monitoring.

Two tetranuclear Cd-based metal–organic frameworks for sensitive sensing of TNP/Fe3+ in aqueous media and gas adsorption

Two Cd-MOFs were solvothermally synthesized by mixed-ligand strategy. 1 has the largest adsorption selectivity for CO₂. Furthermore, 1 and 2 present sensitive sensing for TNP/Fe³⁺ in water or soil samples.

Multifunctional polymers with interpenetrating structures: luminescence sensing, ECL behaviors, selective detection of Fe3+ ion and rapid removal of anionic dyes

Three unprecedented metal–organic frameworks with interspersed structures have been synthesized and structurally characterized.

New two-dimensional Cd(ii) coordination networks bearing benzimidazolyl-based linkers as bifunctional chemosensors for the detection of acetylacetone and Fe3+

Two new CPs, namely {[Cd(L)(1,4-PDA)]·0.7(C₂H₅OH)}_n (1) and {[Cd(L)_0.5(1,8-NDC)·H₂O]}_n (2) were fabricated. 1 shows a sql 2D network. 2 shows a 2D 3,4L83 network. Both 1 and 2 were highly selective and sensitive fluorescent chemosensors toward acetylacetone and Fe³⁺.

Multi-responsive chemosensing and photocatalytic properties of three luminescent coordination polymers derived from a bifunctional 1,1′-di(4-carbonylphenyl)-2,2′-biimidazoline ligand

Three 3D Zn^II/Cd^II CPs were synthesized to act as multiresponsive luminescent sensors for Fe³⁺, Cr₂O₇²⁻ and NZF antibiotic. The photocatalytic studies indicate that the CPs 1–3 have good photocatalytic capability in degradation of MB.

Metal/N-donor-induced versatile structures and properties of seven 0D → 3D complexes based on dpq/dppz and O-bridged tricarboxylate: fluorescence and electrochemical behaviors

Seven 0D → 3D coordination polymers based on dpq/dppz and O-bridged tricarboxylates have been hydrothermally synthesized and structurally directed by metal ions, which show different electrochemical and fluorescence behaviors.

Different effects in the selective detection of aniline and Fe3+ by lanthanide-based coordination polymers containing multiple reactive sites

Isostructural Ln-CPs (1-Eu and 2-Tb) show almost the same high detection ability for Fe³⁺ and different detection abilities for aniline. The detection difference was studied through PXRD, UV-vis, luminescence lifetimes and Hirshfeld surface analysis.

Syntheses, characterization and properties of three coordination polymers with interpenetrating structures comprising 4,4'-(1H-1,2,4-triazol-1-yl)methylene-bis(benzonic acid)

Three new coordination polymers (CPs), {[Pb(tmdb)](H₂O)} _n (1), {[Zn(tmdb)(bimb)_0.5]} _n (2) and {[Zn₃(tmdb)₃(bpmb)_1.5](H₂O)₆} _n (3) (H₂tmdb = 4,4'-(1H-1,2,4-triazol-1-yl)methylene-bis(benzonic acid), where bpmb = 1,4-bis(pyridin-4-ylmethoxy)benzene and bimb = 1,4-bis(imidazoly-1-yl)benzene), have been solvothermally or hydrothermally synthesized. Compound 1 is a 2D network with the point symbol (4·6·8)(4·6²) and compound 2 is a 4-fold interpenetrating 3D network with spiral chains. The topological type of 2 is dmc (topos&RCSR.ttd) with the point symbol (4·8²)(4·8⁵). Compound 3 is a 3-fold interpenetrating 3D network with the point symbol (6³)₂(8·6⁵)₂(10·6²)(8·10·6⁴). The electrochemiluminescence (ECL) behaviors of 2 and 3 were studied. The applications of CP 2 and 3 in detecting ions were explored, and the results show that they can be used as fluorescent probes to selectively detect and identify Fe³⁺ ions in water. In addition, the applications of CP 2 and 3 in the adsorption and separation of dyes were researched. Furthermore, the gas adsorption of 3 was studied.