Morphology-dependent sensing performance of dihydro-tetrazine functionalized MOF toward Al(III)

Isoreticular Metal-Organic Framework-3 (IRMOF-3): From Experimental Preparation, Functionalized Modification to Practical Applications

Isoreticular metal-organic framework-3 (IRMOF-3), a porous coordination polymer, is an MOF material with the characteristics of a large specific surface area and adjustable pore size. Due to the existence of the active amino group (-NH2) on the organic ligand, IRMOF-3 has more extensive research and application potential. Herein, the main preparation methods of IRMOF-3 in existing research were compared and discussed first. Second, we classified and summarized the functionalization modification of IRMOF-3 based on different reaction mechanisms. In addition, the expanded research and progress of IRMOF-3 and their derivatives in catalysis, hydrogen storage, material adsorption and separation, carrier materials, and fluorescence detection were discussed from an application perspective. Moreover, the industrialization prospect of IRMOF-3 and the pressing problems in its practical application were analyzed and prospected. This review is expected to provide a reference for the design and application of more new nanomaterials based on IRMOF-3 to develop more advanced functional materials in industrial production and engineering applications.

The Application of Metal-Organic Frameworks in Water Treatment and Their Large-Scale Preparation: A Review

Over the last few decades, there has been a growing discourse surrounding environmental and health issues stemming from drinking water and the discharge of effluents into the environment. The rapid advancement of various sewage treatment methodologies has prompted a thorough exploration of promising materials to capitalize on their benefits. Metal-organic frameworks (MOFs), as porous materials, have garnered considerable attention from researchers in recent years. These materials boast exceptional properties: unparalleled porosity, expansive specific surface areas, unique electronic characteristics including semi-conductivity, and a versatile affinity for organic molecules. These attributes have fueled a spike in research activity. This paper reviews the current MOF-based wastewater removal technologies, including separation, catalysis, and related pollutant monitoring methods, and briefly introduces the basic mechanism of some methods. The scale production problems faced by MOF in water treatment applications are evaluated, and two pioneering methods for MOF mass production are highlighted. In closing, we propose targeted recommendations and future perspectives to navigate the challenges of MOF implementation in water purification, enhancing the efficiency of material synthesis for environmental stewardship.

Multifunctional Roles of Dihydrotetrazine-Decorated Zr-MOFs in Photoluminescence and Colorimetrism for Discrimination of Arsenate and Phosphate Ions in Water

The high chemical and structural stabilities of zirconium (Zr)-based metal-organic frameworks (MOFs) in aquatic media make them ideal candidates for wastewater treatment. Rational decoration or Zr-MOFs with functional groups can significantly extend their application in this area. In this work, two well-known Zr-MOFs, UiO-66 and MIL-140-A, were functionalized with dihydrotetrazine function to increase their capability in water treatment. Investigations reveal that these two dihydrotetrazine (DHTZ)-functionalized MOFs, namely UiO-66(Zr)-DHTZ and MIL-140(Zr)-DHTZ, can be applied as a two-component array for highly selective and sensitive discrimination of arsenate (AsO43-) and phosphate (PO43-) ions in water in the presence of other anions. Photoluminescence (PL) tests using UiO-66(Zr)-DHTZ show that this MOF can detect these two anions via a ratiometric response, 1.74 for arsenate and 1.84 for phosphate at 2 μM, with superior detection limits (7.2 × 10-8 M for AsO43- and 4.3 × 10-8 M for PO43-). The ratiometric PL response of UiO-66(Zr)-DHTZ toward arsenate and phosphate anions arises possibly from the arsenate-dihydrotetrazine hydrogen bonding. In the next step, colorimetric tests using MIL-140(Zr)-DHTZ were conducted to discriminate the arsenate from phosphate with a very low detection limit at nanomolar level. This MOF undergoes a yellow-to-pink color change in the presence of arsenate ions, while no color change is observed in the presence of phosphate. This color change is observed through conversion of dihydrotetrazine sites inside the pores of MIL-140(Zr)-DHTZ into tetrazine. Altogether, the PL response of UiO-66(Zr)-DHTZ is originated from the hydrogen bond-donating/accepting character of DHTZ function, while the colorimetric response of MIL-140(Zr)-DHTZ is based on the chemical conversion of DHTZ function. This work clearly shows that the decoration of Zr-based MOFs with multicharacter functional groups can develop their application in wastewater treatment as multipurpose platforms.

Recent Developments in Sonochemical Synthesis of Nanoporous Materials

Ultrasounds are commonly used in medical imaging, solution homogenization, navigation, and ranging, but they are also a great energy source for chemical reactions. Sonochemistry uses ultrasounds and thus realizes one of the basic concepts of green chemistry, i.e., energy savings. Moreover, reduced reaction time, mostly using water as a solvent, and better product yields are among the many factors that make ultrasound-induced reactions greener than those performed under conventional conditions. Sonochemistry has been successfully implemented for the preparation of various materials; this review covers sonochemically synthesized nanoporous materials. For instance, sonochemical-assisted methods afforded ordered mesoporous silicas, spherical mesoporous silicas, periodic mesoporous organosilicas, various metal oxides, biomass-derived activated carbons, carbon nanotubes, diverse metal-organic frameworks, and covalent organic frameworks. Among these materials, highly porous samples have also been prepared, such as garlic peel-derived activated carbon with an apparent specific surface area of 3887 m2/g and MOF-177 with an SSA of 4898 m2/g. Additionally, many of them have been examined for practical usage in gas adsorption, water treatment, catalysis, and energy storage-related applications, yielding satisfactory results.

A Dihydrotetrazine-Functionalized Metal-Organic Framework as a Highly Selective Luminescent Host-Guest Sensor for Detection of 2,4,6-Trinitrophenol

Pore decoration of metal-organic frameworks (MOFs) with functional groups is a useful strategy to attain high selectivity toward specific analytes, especially in the presence of interfering molecules with similar structures and energy levels, through selective host-guest interactions. In this work, we applied a dihydrotetrazine-decorated MOF, TMU-34, with the formula [Zn(OBA)(H₂DPT)_0.5]_n·DMF, where H₂OBA is 4,4'-oxybis(benzoic acid) and H₂DPT is 3,6-bis(pyridin-4-yl)-1,4-dihydro-1,2,4,5-tetrazine, for the highly selective detection of phenolic NACs, especially TNP (94% quenching efficiency, detection limit 8.1 × 10^-6 M, K_SV = 182663 mol L^-1), in the presence of other substituted NACs especially -NH₂-substituted NACs. Investigations reveal that the quenching mechanism is dominated by photoinduced MOF-to-TNP electron transfer through possible hydrogen-bonding interactions between the phenolic hydroxyl group of TNP and dihydrotetrazine functions of TMU-34. Despite extensive publications on the detection of TNP in the presence of other NACs, the significance of this work will be elucidated if attention is paid to the fact that TMU-34 is among the rare and highly selective MOF-based TNP sensors in the presence of -NH₂-substituted NACs as the serious interferers.

State of the art on the ultrasonic-assisted removal of environmental pollutants using metal-organic frameworks

The environmental and health issues of drinking water and effluents released into nature are among the major area of contention in the past few decades. With the growth of ultrasound-based approaches in water and wastewater treatment, promising materials have also been considered to employ their advantages. Metal-organic frameworks (MOFs) are among the porous materials that have received great attention from researchers in recent years. Features such as high porosity, large specific surface area, electronic properties like semi-conductivity, and the capacity to coordinate with the organic matter have resulted in a substantial increase in scientific researches. This work deals with a comprehensive review of the application of MOFs for ultrasonic-assisted pollutant removal from wastewater. In this regard, after considering features and synthesis methods of MOFs, the mechanisms of several ultrasound-based approaches including sonocatalysis, sonophotocatalysis, and sono-adsorption are well assessed for removal of different organic compounds by MOFs. These methods are compared with some other water treatment processes with the application of MOFs in the absence of ultrasound. Also, the main concern about MOFs including environmental hazards and water stability is fully discussed and some techniques are proposed to reduce hazardous effects of MOFs and improve stability in humid/aqueous environments. Economic aspects for the preparation of MOFs are evaluated and cost estimates for ultrasonic-assisted AOP approaches were provided. Finally, the future outlooks and the new frontiers of ultrasonic-assisted methods with the help of MOFs in global environmental pollutant removal are presented.

Metal–organic frameworks (MOFs) as fluorescence sensors: principles, development and prospects

This review classifies the latest developments of MOF-based fluorescence sensors according to the analytes, and discusses the challenges faced by MOF-based fluorescence sensors and promotes some directions for future research.

Response of a Zn(II)-based metal-organic coordination polymer towards trivalent metal ions (Al3+, Fe3+ and Cr3+) probed by spectroscopic methods

A new zinc-based two-dimensional coordination polymer, [Zn(5-AIP)(Ald-4)]·H2O (5-AIP = 5-amino isophthalate, Ald-4 = aldrithiol-4), 1, has been synthesized at room temperature by the layer diffusion technique. Single-crystal X-ray diffraction analysis of 1 showed a two-dimensional bilayer structure. An aqueous suspension of 1 upon excitation at 300 nm displayed an intense blue emission at 403 nm. The luminescence spectra were interestingly responsive and selective to Al3+, Cr3+ and Fe3+ ions even in the presence of other interfering ions. The calculated detection limits for Al3+, Cr3+ and Fe3+ were 0.35 μM ([triple bond, length as m-dash]8.43 ppb), 0.46 μM ([triple bond, length as m-dash]22.6 ppb) and 0.30 μM ([triple bond, length as m-dash]15.85 ppb), respectively. Notably, with the cumulative addition of Al3+ ions, the luminescence intensity at 403 nm decreased steadily with a gradual red shift up to 427 nm. Afterward, this red shifted peak showed a turn-on effect upon further addition of Al3+ ions. On the other hand, for Cr3+ and Fe3+ ions, there was only drastic luminescence quenching and a large red shift up to 434 nm. This indicated the formation of a complex between 1 and these metal ions, which was also supported by the UV-Visible absorption spectra of 1 that showed the appearance of a new band at 280 nm in the presence of these three metal ions. The FTIR spectra revealed that these ions interacted with the carboxylate oxygen atom of 5-AIP and the nitrogen atom of the Ald-4 ligand in the structure. The luminescence lifetime decay analysis manifested that a charge-transfer type complex was formed between 1 and Cr3+ and Fe3+ ions that resulted in huge luminescence quenching due to the efficient charge transfer involving the vacant d-orbitals, whereas for Al3+ ions having no vacant d-orbital, turn-on of luminescence occurred because of the increased rigidity of 1 upon complexation.

A power-triggered preparation strategy of nano-structured inorganics: sonosynthesis

Ultrasound irradiation covers many chemical reactions crucially aiming to design and synthesize various structured materials as an enduring trend in frontier research studies. Here, we focus on the latest progress of ultrasound-assisted synthesis and present the basic principles or mechanisms of sonosynthesis (or sonochemical synthesis) from ultrasound irradiation in a brand new way, including primary sonosynthesis, secondary sonosynthesis, and synergetic sonosynthesis. This current review describes in detail the various sonochemical synthesis strategies for nano-structured inorganic materials and the unique aspects of products including the size, morphology, structure, and properties. In addition, the review points out the probable challenges and technological potential for future advancement. We hope that such a review can provide a comprehensive understanding of sonosynthesis and emphasize the great significance of structured materials synthesis as a power-induced strategy broadening the updated applications of ultrasound.

Sonochemical fabrication of inorganic nanoparticles for applications in catalysis

Catalysis covers almost all the chemical reactions or processes aiming for many applications. Sonochemistry has emerged in designing and developing the synthesis of nano-structured materials, and the latest progress mainly focuses on the synthetic strategies, product properties as well as catalytic applications. This current review simply presents the sonochemical effects under ultrasound irradiation, roughly describes the ultrasound-synthesized inorganic nano-materials, and highlights the sonochemistry applications in the inorganics-based catalysis processes including reduction, oxidation, degradation, polymerization, etc. Or all in all, the review hopes to provide an integrated understanding of sonochemistry, emphasize the great significance of ultrasound-assisted synthesis in structured materials as a unique strategy, and broaden the updated applications of ultrasound irradiation in the catalysis fields.

Syntheses, design strategies, and photocatalytic charge dynamics of metal–organic frameworks (MOFs): a catalyzed photo-degradation approach towards organic dyes

The presented review focuses on design strategies to develop tailor-made MOFs/CPs of main group, transition and inner-transition elements and their photocatalytic properties to decompose dyes in wastewater discharge and their photocatalytic mechanism.

Dual-emitting barium based metal-organic nanosheets as a potential sensor for temperature and anthrax biomarkers

The development of novel 2D materials, due to the promising applications they have enabled through their unique properties, has attracted increasingly more research interest. In this regard, novel dual-emitting coordination polymer nanosheets were developed by doping Eu³⁺ and Tb³⁺ ions into the nanostructures of the [Ba(DPA)₂(H₂O)₂] _n (DPA = dipicolinic acid) coordination polymer (BCP). Single crystal x-ray crystallography revealed that BCP is a 1D coordination polymer and its three-dimensional supramolecular architecture is constructed with a relatively strong hydrogen bonding in the ac crystallographic plane and weak non-covalent interactions along the b axis. Using energetic ultrasound irradiations, synthesis of nanoscale BCP along with the unzipping of the weak interactions between the ac layers was accomplished. The resulting BCP nanosheets was used as the host lattice and was doped with Eu³⁺ and Tb³⁺ ions. Remarkably, the sensing ability of both Eu³⁺ and Tb³⁺ doped coordination polymer (Ln@BCP) nanosheets towards temperature and the DPA anthrax biomarker were investigate. The high relative sensitivity value of 2.42% K^-1 and their reusability, makes Ln@BCP nanosheets an ideal candidate for the nanothermometry. They also exhibited high selective detection characteristics towards the DPA anthrax biomarker with a 0.03 nM detection limit. Therefore, Ln@BCP nanosheets can also be considered as an efficient multi-responsive optical sensor.

Dramatic luminescence signal from a Co(ii)-based metal–organic compound due to the construction of charge-transfer bands with Al3+ and Fe3+ ions in water: steady-state and time-resolved spectroscopic studies

A Co(ii)-based metal–organic compound exhibits luminescence turn-on by Al³⁺ and quenching by Fe³⁺ due to the formation of charge-transfer complexes/adducts.

Controlling the morphology of metal–organic frameworks and porous carbon materials: metal oxides as primary architecture-directing agents

We give a comprehensive overview of how the morphology control is an effective and versatile way to control the physicochemical properties of metal oxides that can be transferred to metal–organic frameworks and porous carbon materials.

An adjustable dual-emission fluorescent metal-organic framework: Effective detection of multiple metal ions, nitro-based molecules and DMA

A novel multifunctional Pb(II)-based MOF, [Pb_1.5(DBPT)]₂·(DMA)₃(H₂O)₄ (1), with excellent chemical stability, was successfully assembled by connecting {Pb₂O₁₀} unit with a multi-topic polycarboxylate ligand of 3-(3,5-dicarboxylphenyl)-5-(4-carboxylphenyl)-1-H-1,2,4-triazole (H₃DBPT). It exhibits dual fluorescence emissions at 380 nm (λ_ex = 280 nm) and 540 nm (λ_ex = 380 nm), respectively. Through the adjustable dual fluorescence emissions, it could act as a turn-off and turn-on switch for detecting N,N-dimethylacetamide (DMA) molecule. Moreover, Fe³⁺ ions exert luminescence quenching role on compound 1 at both excitation lengths in water, among which the quenching at λ_ex = 280 nm is of high sensitivity (K_SV = 1.2 × 10⁵), and the quenching at λ_ex = 380 nm is of wide-range. The sensing for metal ions of In³⁺, Zr⁴⁺, and Al³⁺ is also effective at λ_ex = 280 nm, with the K_SV constants of 1.6 × 10⁵, 1.6 × 10⁵, and 4.3 × 10⁴, respectively. More importantly, a series of nitroaromatic compounds (TNP, 2,4,6-trinitrophenol; 4-NA, 4-nitroaniline; NB, nitrobenzene) and nitro-based drugs (MNZ, metronidazole; DMZ, dimetridazole) could be detected at both excitation lengths, demonstrating the advantage of broad range response of fluorescence sensing. Thanks to the excellent chemical stability and unusual dual emission luminescence properties for chemical detection of various metal ions, nitro-based molecules and DMA solvent, the Pb-based MOF reported in this work is, therefore, a very promising multi-response sensor.

Function-Structure Relationship in Metal-Organic Frameworks for Mild, Green, and Fast Catalytic C-C Bond Formation

Tunability in chemical functionality is a promising characteristic of metal-organic frameworks (MOFs), which plays an important role in developing and improving the practical applications of MOFs. Here, we applied this important feature of MOFs to be in line with sustainable development and green chemistry principles through the synthesis of MOF-based heterogeneous organocatalysts. According to our green functionalization strategy, some isostructural MOFs (azine decorated TMU-4 with the formula [Zn(OBA)(BPDB)_0.5]_n·2DMF, azine-methyl functionalized TMU-5 with the formula [Zn(OBA)(BPDH)_0.5]_n·1.5DMF, dihydro-tetrazine decorated TMU-34 with the formula [Zn(OBA)(H₂DPT)_0.5]_n·DMF, and tetrazine functionalized TMU-34(-2H) with the formula [Zn(OBA)(DPT)_0.5]_n·DMF, where H₂OBA = 4,4'-oxybis(benzoic acid), BPDB = 1,4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene, BPDH = 2,5-bis(4-pyridyl)-3,4-diaza-2,4-hexadiene, H₂DPT = 3,6-di(pyridin-4-yl)-1,4-dihydro-1,2,4,5-tetrazine, and DPT = 3,6-di(pyridin-4-yl)-1,2,4,5-tetrazine) have been applied for mild, green, and fast Knoevenagel condensation. These frameworks display different Lewis basic catalytic activities owing to their different functionality and function accessibility. Contrary to extensive articles published about Knoevenagel condensation, this study involves the rare examples in Knoevenagel condensation with such mild conditions (room temperature and atmospheric pressure) and with a green solution (water as the solvent). Due to the combined synergic effects of the Lewis basicity of TMU-frameworks, the amphoteric and hydrogen bond-participating nature of water molecules, maximum conversion times are reached just after 30 min (for TMU-5) and 60 min (for TMU-34). Stability and recyclability tests show that TMU-5 and TMU-34 are completely stable in water at reaction conditions and can retain their crystallinity, porosity, and functionality even after five cycles without any specific reduction in their catalytic conversion. Since, in many cases, amine decorated MOFs are applied in Knoevenagel catalyzed condensation, this study is beneficial in providing information about the effects of azine and tetrazine functional groups in reactant activation and the acceleration of Knoevenagel condensation.

High Capacity Oil Denitrogenation over Azine- and Tetrazine-Decorated Metal-Organic Frameworks: Critical Roles of Hydrogen Bonding

In this work, we demonstrate that rational decoration of pore walls of the metal-organic frameworks (MOFs) with azine and dihydro-tetrazine functions is a very practical strategy for high capacity removal of both neutral and basic nitrogen-containing compounds (NCCs) from model oil. Its performance is even much better than the MOFs with high surface area, open metal sites, and different functional groups such as amine, hydroxyl, carboxy, and sulfonate. For this aim, a number of isostructure functional MOFs (FMOFs) have been synthesized. Among them, TMU-5 (with formula [Zn(OBA)(BPDH)_0.5] _n·1.5DMF, where H₂OBA = 4,4'-oxybis(benzoic acid) and BPDH = 2,5-bis(4-pyridyl)-3,4-diaza-2,4-hexadiene) and TMU-34 (with formula [Zn(OBA)(H₂DPT)_0.5] _n·DMF H₂DPT = 3,6-di(pyridin-4-yl)-1,4-dihydro-1,2,4,5-tetrazine) show high affinity toward neutral and basic NCCs, respectively. Dihydro-tetrazine-decorated TMU-34 shows good affinity toward basic NCCs [pyridine (PYD) and quinoline (QUI)] because of hydrogen bonding of dihydro-tetrazine (-NH)···(N) basic NCCs. TMU-34 can adsorb about 619 and 632 mg g^-1 PYD and QUI, respectively. On the other hand, azine-methyl-functionalized TMU-5 shows very high affinity to neutral NCCs [pyrrole (PRR) and indole (IND)] owing to strong hydrogen bonding of azine-methyl (Me-C═N-N═C-Me)···(NH) neutral NCCs. TMU-5 can adsorb 518 and 578 mg g^-1 PRR and IND, respectively. These numbers are among the best reported data in this area and even reveal higher significance of the host-guest interaction when we consider moderate surface of these FMOFs. These results have been achieved by our "application-directed cavity functionalization" approach through decoration of MOF structures by suitable organic functional groups for specific purposes.

Metal Organic Frameworks (MOFs) and ultrasound: A review

Metal-organic frameworks (MOFs) have received a lot of attention due to their unique properties and abundant functionalities. Permanent porosity and high surface area are just a few traits that have made them attractive to researchers. They can be prepared as task-specific materials by exploiting the functional group variety and tuning their size and geometry. The main purpose of this review is to present an alternative method of preparing MOF crystals and underline the advantages of ultrasound assisted (sonochemical) synthesis. State of the art ultrasound assisted techniques for the preparation of MOFs in nanoscale are presented. Optimization of morphology and particle size is highlighted throughout this work, as we discuss the effects of various factors, such as energy input, reagent concentration, adequate solvents, reaction time and more.

Fast ultrasound-assisted synthesis of highly crystalline MIL-88A particles and their application as ethylene adsorbents

Highly crystalline MIL-88A particles have been successfully synthesized via fast ultrasound-assisted processes. The influence of the sonication generator and synthesis time on the structure, crystallinity, morphology and surface area of the materials were studied in detail. Under this modified ultrasonic method, X-ray diffraction patterns of MIL-88A particles showed highly crystalline structures in contrast to those reported in literature. Significant differences on surface areas and microporosity were appreciated under ultrasound conditions employed. Specific surface areas in the range between 179 and 359 m² g^-1 were obtained. That material synthesized under ultrasound batch conditions during 1 h had the highest surface area and microporous character. Different particle sizes and morphologies were obtained depending on the synthesis procedure. In general, probe sonicators led to smaller particle sizes. Moreover, a comparative study of the ethylene adsorption of the MIL-88A particles and several common MOFs in the ethylene adsorption was investigated. The results suggest that the modified ultrasound-assisted procedure for the synthesis of MIL-88A is effective to obtain highly crystalline particles, which are very efficient to adsorb ethylene molecules.

Sonochemical synthesis and properties of two new nanostructured silver(I) coordination polymers

Two new Ag(I) coordination polymers (CPs), namely, Ag(L)(Htp) (1) and [Ag(L)]·(Htp)·2H₂O (2) were synthesized from the long flexible ligand of 1,6-bis(2-methylbenzimidazolyl)hexane (L), terephthalic acid (H₂tp) and different silver(I) salts using hydrothermal and sonochemical methods, These CPs were characterized by elemental analysis, IR spectra, scanning electron microscopy, single-crystal and powder X-ray diffraction analysis. 1 features a uninodal 3-connected 2D hcb layered structure, while 2 exhibits an infinite 1D linear chain and ultimately extended into 3D supramolecular framework via O-H⋯O and Ag⋯O interactions. In addition, the effect of various sonication concentrations of the initial reagents, ultrasonic time and power of ultrasound irradiation on the size and morphology of nanostructured 1 and 2 were evaluated. Nano-sized 1 and 2 exhibit relatively high performance as UV light driven photocatalysts for the degradation of methylene blue.