Europium ion post-functionalized zirconium metal–organic frameworks as luminescent probes for effectively sensing hydrazine hydrate

Fabrication and DFT Calculation of Amine-Functionalized Metal-Organic Framework as a Turn-On Fluorescence Sensor for Fe3+ and Al3+ Ions

Due to their important role in biological systems, it is urgent to develop a material that can rapidly and sensitively detect the concentration of Fe³⁺ and Al³⁺ ions. In this work, a brand-new Cd^II-based metal-organic framework [Cd(BTBD)₂(AIC)]_n (JXUST-18, BTBD = 4,7-bis(1H-1,2,4-triazol-1-yl)-2,1,3-benzothiadiazole and H₂AIC = 5-aminoisophthalic acid) with a 4-connected sql topology was designed and synthesized. The symmetrical Cd^II centers are linked by AIC^2- ligands with μ₃-η¹:η¹:η¹:η¹ coordination mode to form a [Cd₂(COO)₂] secondary building unit (SBU). The contiguous SBUs are further connected by BTBD ligands to form a two-dimensional (2D) layer structure. JXUST-18 can remain stable in aqueous solutions with pH values of 3-12 or in boiling water. Luminescent experiments suggest that JXUST-18 displays more than eightfold fluorescence enhancement in the presence of Fe³⁺ and Al³⁺ ions, and the detection limits for Fe³⁺ and Al³⁺ ions are 0.196 and 0.184 μM, respectively. Furthermore, the change in luminescence color is uncomplicatedly distinguishable with the naked eye under ultraviolet light at 365 nm. In addition, a series of devices based on JXUST-18 including fluorescence test strips, lamp beads, and composite films were developed to detect metal ions via visual changes in luminescence color. Significantly, JXUST-18 is a rare MOF-based turn-on fluorescence sensor for the detection of Fe³⁺ ions. The theoretical calculation suggests that the complexation of Fe³⁺/Al³⁺ ions and the -NH₂ group contributes to fluorescence enhancement.

The Application of Modified SBA-15 as a Chemosensor

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The Santa Barbara Amorphous (SBA-15), with a large surface area covered with abundant Si-OH active groups on the walls of its pores, can be modified with various organic compounds to build organic-inorganic hybrid materials, which can be used as a catalyst in organic reactions, drug delivery systems, nano sorbent due to its high capacity for removing heavy metals in waste water and as chemosensors for ions. Tunable and straight channels of SBA-15 facilitate the entrance and diffusion of ions through the channels. This paper presents a review of the past five years of literature covering the application of SBA-15 as an ions chemosensor in the liquid and gaseous media.

Novel ratiometric fluorescent probe based on internal reference and its detection of hydrazine

In this work, dual-emissive ratiometric fluorescent system was constructed by the introduction of an ideal internal reference. By virtue of its unique alkalinity, N₂H₄ could undergo a hydrazinolysis reaction with the ester group of F1, inducing remarkable fluorescence enhancement while the blue fluorescence of the internal reference DPA remained constant. Consequently, the fluorescence intensity ratios (I₅₄₀/I₄₄₀) were proportional to the concentrations of N₂H₄, which was beneficial for the exactly quantitative detection. The skillful strategy granted the sensing system advantages such as relative good solubility in aqueous media, easy-to-design, simple synthesis, large emission shift, good ratiometric response, as well as the successful application in real water samples and cell imaging.

Macro-Meso-Microporous Metal-Organic Frameworks: Template-Assisted Spray Drying Synthesis and Enhanced Catalysis

Hierarchically porous metal-organic frameworks (HP-MOFs) are promising in many applications. However, most previous studies focus on HP-MOFs with two kinds of pore structures. Herein, a strategy for efficient construction of HP-MOFs possessing macro-meso-micropores using template-assisted spray drying followed by etching process is proposed. Taking ZIF-8 as an example, using polystyrene (PS) templates, the complete HP-ZIF-8 with all the three categories of pores can be easily fabricated. The close arrangement of intrinsic microporous nanosized ZIF-8 (N-ZIF-8) in the spray drying process results in the creation of mesopores, while the macropores are further generated after the removal of PS templates. The structures of macropores and mesopores can be easily adjusted by altering the size and proportion of PS and the size of N-ZIF-8, respectively. Furthermore, this method is extended to the preparation of HP-HKUST-1. As a proof-of-concept, HP-ZIF-8 displays excellent catalytic properties in Knoevenagel reaction owing to its unique pore features. Compared with conventional microsized ZIF-8 (M-ZIF-8) with similar size, HP-ZIF-8 achieves the significantly increased conversion of benzaldehyde from 55% to 100% within 3 h, and shows better recycling performance than N-ZIF-8.

Group 4 Metal-Based Metal—Organic Frameworks for Chemical Sensors

Metal-organic frameworks (MOFs) have attracted great attention for their applications in chemical sensors mainly due to their high porosity resulting in high density of spatially accessible active sites, which can interact with the aimed analyte. Among various MOFs, frameworks constructed from group 4 metal-based (e.g., zirconium, titanium, hafnium, and cerium) MOFs, have become especially of interest for the sensors requiring the operations in aqueous media owing to their remarkable chemical stability in water. Research efforts have been made to utilize these group 4 metal-based MOFs in chemosensors such as luminescent sensors, colorimetric sensors, electrochemical sensors, and resistive sensors for a range of analytes since 2013. Though several studies in this subfield have been published especially over the past 3–5 years, some challenges and concerns are still there and sometimes they might be overlooked. In this review, we aim to highlight the recent progress in the use of group 4 metal-based MOFs in chemical sensors, and focus on the challenges, potential concerns, and opportunities in future studies regarding the developments of such chemically robust MOFs for sensing applications.

A New Molecular Recognition Concept: Multiple Hydrogen Bonds and Their Optically Triggered Proton Transfer in Confined Metal-Organic Frameworks for Superior Sensing Element

We report a new sensing mechanism based on an indium-dihydroxyterephthalic acid metal-organic framework (MOF, SNNU-153), in which the spatially fitted analyte-MOF hydrogen-bond (H-bond) formation provides selective recognition while the analyte-H-bond assisted excited-state intramolecular proton transfer (ESIPT) and the resulting ratiometric emission act as a superior signal transducer with ultrafast response. The synergy of ESIPT signal transduction and confined MOF pore enables the SNNU-153 sensor selectively sensing hydrazine even among nitrogen-containing hydride analogs such as NH₃, NH₂OH, and (Me)₂NNH₂. The key of H-bond and associated ESIPT was further counter evidenced by an indium-2,5-dimethoxyterephthalic acid MOF (SNNU-152), where the hydroxyl protons were removed by methylation, showing near inertness to N₂H₄. The new molecular recognition concept thus makes SNNU-153 a powerful N₂H₄ sensor, which should be far-reaching to other sensing elements.

Dual-Mode Photonic Sensor Array for Detecting and Discriminating Hydrazine and Aliphatic Amines

Colorimetric chemosensors have attracted tremendous interest for sensing hazardous substances in an uncomplicated and economical manner. Herein, a series of push-pull dicyanovinyl-substituted oligothiophene derivatives were designed, and the impacts of different end-cappers on their photophysical properties were comprehensively investigated. Interestingly, combined with a zinc porphyrin derivative (Zn-TPP), one dicyanovinyl-substituted oligothiophene derivative (NA-3T-CN) can be further developed into colorimetric and fluorescent sensor array for dual-mode detection of aliphatic amines and hydrazine. The obtained sensors showed satisfactory results between optical response and analyte's concentration both in selective single-sensor type and in enhanced multisensory mode. Based on the fluorescence change of the NA-3T-CN system, the detection limit for N₂H₄ was calculated to be around 1.22 × 10^-5 mol/L in THF. The stained TLC-supported sensor array offers obvious optical changes for down to 0.5 wt % hydrazine solution for naked-eye sensing. An aromatic amine like aniline has no obvious effect on the dicyanovinyl-substituted oligothiophene derivatives. We also found that a zinc porphyrin derivative has an obvious colorimetric response to the presence of hydrazine, ethanolamine, and aniline. Furthermore, smartphone-enabled readout system and data treatment based on RGB changes of the sensor array were performed, and the discrimination capability among hydrazine, aliphatic amines, and aromatic amine was satisfactory. In this regard, related push-pull oligothiophene derivatives not only can be regarded as models for a fundamental understanding of the relationship between molecular structure and photophysical properties but also present potential applications in the field of real-time and visual detection of hazardous chemicals.

A novel 'turn-on' coumarin-based fluorescence probe with aggregation-induced emission (AIE) for sensitive detection of hydrazine and its imaging in living cells

An aggregation-induced emission (AIE)- and intramolecular charge transfer (ICT)-based probe 1 (7‑hydroxy‑3‑(3‑methyl‑isoxazol‑5‑yl)‑chromen‑2‑one) that is highly selective for N₂H₄ has been synthesized, exhibiting a 'turn-on' response toward N₂H₄ in CH₃CN/H₂O solution. The detection limit of the probe was 2.90 ppb, which was evidently lower than the threshold limit value (10 ppb) recommended by the Environmental Protection Agency. Notably, the sensor could be used for the detection of N₂H₄ in living cells.

A phthalimide-functionalized UiO-66 metal–organic framework for the fluorogenic detection of hydrazine in live cells

A phthalimide-functionalized Zr(iv) UiO-66 MOF was utilized for fluorogenic detection of hydrazine in HEPES buffer and inside living cells.