Fourier transform infrared and raman spectra, vibrational assignment and ab initio calculations of terephthalic acid and related compounds

Portable on-off visual-mode detection using intrinsic fluorescent zinc-based metal-organic framework for detection of diclofenac in pharmaceutical tablets

On-site, robust, and quantitative detection of diclofenac (DCF) is highly significant in bioanalysis and quality control. Fluorescence-based metal-organic frameworks (MOFs) play a pivotal role in biochemical sensing, offering a versatile platform for detecting various biomolecules. However, conventional fluorescent MOF sensors often rely on lanthanide metals, which can pose challenges in terms of cost, accessibility, and environmental impact. Herein, an intrinsic blue fluorescent zinc-based metal-organic framework (FMOF-5) was prepared free from lanthanide metals. Coordination-induced emission as an effective strategy was followed wherein a non-fluorescent ligand is converted to a fluorescent one after insertion in a framework. Conventional fluorometry and smartphone-assisted visual methods were employed for the detection of DCF. The fluorescence emission of the FMOF-5 was effectively quenched upon the addition of the DCF, endowing it an "off" condition, which permits the construction of a calibration curve with a wide linear range of 30-670 µM and a detection limit of about 4.1 µM. Other analytical figures of merit, such as linearity, sensitivity, selectivity, accuracy, and precision were studied and calculated. Furthermore, the proposed sensor was successfully applied to quantify DCF in pharmaceutical tablets with reliable recovery and precision. Importantly, the elimination of lanthanide metals from the fluorescence detection system enhances its practicality and sustainability, making it a promising alternative for DCF detection in pharmaceutical analysis applications.

Direct monitoring of the enzymatically sequestering and degrading of PET microplastics using hyperspectral Raman microscopy

Microplastics are commonly referred to as tiny plastic fragments polluting our environment, although their nanometric forms have also been found in our drinking water supplies and many living systems. Their removal is relevant for preserving our health and sustainability and is being pursued according to many different strategies, including filtration through selective porous materials or agglomeration using flocculant agents. An alternative nanotechnological approach described in this paper deals with the capture and degradation of micro and nanoplastics by enzyme-immobilized magnetic nanoparticles. Magnetic nanoparticles (Fe3O4) were functionalized with polydopamine (PDA) and Lipase enzyme straightforwardly to generate agents capable of removing and degrading µPET from an aqueous solution. In addition to synthesizing and characterizing the Fe3O4@PDA-Lipase nanoparticles and performing the µPET degradation, the novelty encompassed in this work is the successful use of confocal Raman microscopy to monitor the process, in real-time, through in situ hyperspectral images.

Ultrasonic synthesis, characterization, DFT and molecular docking of a biocompatible Zn-based MOF as a potential antimicrobial, anti-inflammatory and antitumor agent

Zinc metal-organic frameworks have emerged as promising candidates, demonstrating excellent biological properties stemming from the unique characteristics of MOFs and zinc. In this study, we employed a facile method to synthesize a zinc metal-organic framework [Zn(IP)(H2O)] using ultrasound irradiation, with the linker being isophthalic acid (IPA) (1,3-benzene dicarboxylic acid). The parent Zn-MOF and two Ag/Zn-MOF samples prepared via loading and encapsulation methods were comprehensively characterized using various techniques, including FT-IR, XRD, SEM, TEM, N2 adsorption-desorption isotherm, UV-vis spectroscopy and TGA. The parent Zn-MOF and two Ag/Zn-MOF samples exhibited a broad spectrum of antibacterial effects. Remarkably, genomic DNA of P. aeruginosa was effectively degraded by Zn-MOF, further supporting its potent antibacterial results. The free radical inhibition assay demonstrated a 71.0% inhibition under the influence of Zn-MOF. In vitro cytotoxicity activity of Zn-MOF against HepG-2 and Caco-2 cell lines revealed differential cytotoxic effects, with higher cytotoxicity against Caco-2 as explored from the IC50 values. This cytotoxicity was supported by the high binding affinity of Zn-MOF to CT-DNA. Importantly, the non-toxic property of Zn-MOF was confirmed through its lack of cytotoxic effects against normal lung cell (Wi-38). The anti-inflammatory treatment of Zn-MOF achieved 75.0% efficiency relative to the standard Ibuprofen drug. DFT and docking provided insights into the geometric stability of Zn-MOF and its interaction with active amino acids within selected proteins associated with the investigated diseases. Finally, the synthesized Zn-MOF shows promise for applications in cancer treatment, chemoprevention, and particularly antibacterial purposes.

Investigation of the Sensing Properties of Lanthanoid Metal-Organic Frameworks (Ln-MOFs) with Terephthalic Acid

The solvothermal synthesis of LnCl3.nH2O with terephthalic acid (benzene-1,4-dicarboxylic acid, H2BDC) produced metal-organic frameworks (LnBDC), [Ln2(BDC)3(H2O)4]∞, where Ln = Sm, Eu, Tb, and Dy. The materials obtained were characterized by a number of physico-chemical techniques. The influence of the ionic radius of the lanthanides on the microstructural characteristics of the Ln-MOFs was evaluated by performing Rietveld refinement. The MOFs obtained were tested as fluorescent sensors for numerous cations and anions in water. The highly luminescent EuBDC and TbBDC demonstrated multi-responsive luminescence sensing functions to detect Ag(I), Fe(III), Cr(III), and Cr(VI), which are essential for their environmental applications. By applying the non-linear Stern-Volmer equation, the fluorescent quenching mechanism was determined. The stability of the obtained materials in water in a wide pH range (acidity pH = 4 and alkalinity pH = 9 solutions) was confirmed.

Enhancing visible-light-driven photocatalysis: unveiling the remarkable potential of H2O2-assisted MOF/COF hybrid material for organic pollutant degradation

In this study, we synthesized MOF/COF hybrid material (NH2-MOF-5/MCOF) by integrating NH2-MOF-5 (Zn) with a melamine-based COF (MCOF) to target the photocatalytic degradation of methylene blue (MB) dye. Characterization using SEM, XRD, XPS, FT-IR, and UV-DRS confirmed the synthesized MOF/COF hybrid's exceptional photocatalytic performance under visible light. The addition of H2O2 significantly enhanced the photocatalytic degradation, achieving removal rates of 90%, 92%, and 57% for 11.75 mg L-1, 30 mg L-1, and 83 mg L-1 of MB, respectively. Kinetic studies revealed first-order kinetics, with a rate constant nearly 3.5 times higher with added H2O2. We proposed a comprehensive photocatalytic mechanism elucidated through energy band structure analysis and scavenger tests. Our findings revealed the formation of a heterojunction between NH2-MOF-5 and MCOF, which mitigates electron-hole recombination, with ∙OH identified as the principal species governing methylene blue degradation. Moreover, the NH2-MOF-5/MCOF hybrid displayed excellent reusability and chemical stability over six cycles. Notably, this H2O2-assisted hybrid material demonstrated the removal of 99% of ibuprofen, a pharmaceutical drug, showcasing its broad applicability in removing organic contaminants in aqueous solutions, thereby holding great promise for wastewater treatment.

Depolymerization mechanisms and closed-loop assessment in polyester waste recycling

Alcoholysis of poly(ethylene terephthalate) (PET) waste to produce monomers, including methanolysis to yield dimethyl terephthalate (DMT) and glycolysis to generate bis-2-hydroxyethyl terephthalate (BHET), is a promising strategy in PET waste management. Here, we introduce an efficient PET-alcoholysis approach utilizing an oxygen-vacancy (Vo)-rich catalyst under air, achieving space time yield (STY) of 505.2 gDMT·gcat-1·h-1 and 957.1 gBHET·gcat-1·h-1, these results represent 51-fold and 28-fold performance enhancements compared to reactions conducted under N2. In situ spectroscopy, in combination with density functional theory calculations, elucidates the reaction pathways of PET depolymerization. The process involves O2-assisted activation of CH3OH to form CH3OH* and OOH* species at Vo-Zn2+-O-Fe3+ sites, highlighting the critical role of Vo-Zn2+-O-Fe3+ sites in ester bond activation and C-O bond cleavage. Moreover, a life cycle assessment demonstrates the viability of our approach in closed-loop recycling, achieving 56.0% energy savings and 44.5% reduction in greenhouse-gas emissions. Notably, utilizing PET textile scrap further leads to 58.4% reduction in initial total operating costs. This research offers a sustainable solution to the challenge of PET waste accumulation.

Upcycling of post-consumer polyethylene terephthalate bottles into aluminum-based metal-organic framework adsorbents for efficient orthophosphate removal

2-Phosphonobutane-1,2,4,-tricarboxylic acid (PBTC) is an orthophosphate compound widely used as an antiscalant chemical and corrosion inhibitor in manufacturing. However, PBTC poses persistent environmental concerns due to its stability and resistance to conventional water treatment. In addressing the issues of PBTC in aquatic systems, Al-based metal-organic frameworks (MOFs) have been developed and applied as sustainable adsorbents. The materials are synthesized from terephthalic acid (TPA) linkers derived from upcycling products of post-consumer polyethylene terephthalate (PET) bottles. The PET-derived linker was prepared using alkaline hydrolysis followed by acidification and employed in forming MIL-53 (Al), with a comparative assessment against the corresponding MOFs made from commercial-grade TPA. The structures and properties of the materials were characterized with microscopic and spectroscopic methods. The synthesized adsorbents achieved a phosphate adsorption capacity of 826 mg/g at pH 5, with kinetics fitting a pseudo-second-order model and isotherm patterns aligning with Langmuir, Freundlich, and Sips models, indicative of diverse adsorption on heterogeneous surfaces. The results highlight the role of electrostatic interactions and hydrogen bonding mechanisms in PBTC adsorption. The eco-friendly materials with high adsorption performance offer an innovative route for sustainable waste management and water purification.

Physiochemical characterization of metal organic framework materials: A mini review

Metal-organic frameworks (MOFs) are promising materials offering exceptional performance across a myriad of applications, attributable to their remarkable physicochemical properties such as regular porosity, crystalline structure, and tailored functional groups. Despite their potential, there is a lack of dedicated reviews that focus on key physicochemical characterizations of MOFs for the beginners and new researchers in the field. This review is written based on our expertise in the synthesis and characterization of MOFs, specifically to provide a right direction for the researcher who is a beginner in this area. In this way, experimental errors can be reduced, and wastage of time and chemicals can be avoided when new researchers conduct a study. In this article, this topic is critically analyzed, and findings and conclusions are presented. We reviewed three well-known XRD techniques, including PXRD, single crystal XRD, and SAXS, which were used for XRD analysis depending on the crystal size and the quality of crystal morphology. The TGA profile was an effective factor for evaluating the quality of the activation process and for ensuring the successful investigation for other characterizations. The BET and pore size were significantly affected by the activation process and selective benzene chain cross-linkers. FTIR is a prominent method that is used to investigate the functional groups on pore surfaces, and this method is successfully used to evaluate the activation process, characterize functionalized MOFs, and estimate their applications. The most significant methods of characterization include the X-ray diffraction, which is utilized for structural identification, and thermogravimetric analysis (TGA), which is used for exploring thermal decomposition. It is important to note that the thermal stability of MOFs is influenced by two main factors: the metal-ligand interaction and the type of functional groups attached to the organic ligand. The textural properties of the MOFs, on the other hand, can be scrutinized through nitrogen adsorption-desorption isotherms experiments at 77 K. However, for smaller pore size, the Argon adsorption-desorption isotherm at 87.3 K is preferred. Furthermore, the CO2 adsorption isotherm at 273 K can be used to measure ultra-micropore sizes and sizes lower than these, which cannot be measured by using the N2 adsorption-desorption isotherm at 77 K. The highest BET was observed in high-valence MOFs that are constructed based on the metal-oxo cluster, which has an excellent ability to control their textural properties. It was found that the synthesis procedure (including the choice of solvent, cross-linker, secondary metal, surface functional groups, and temperature), activation method, and pressure significantly impact the surface area of the MOF and, by extension, its structural integrity. Additionally, Fourier-transform infrared spectroscopy plays a crucial role in identifying active MOF functional groups. Understanding these physicochemical properties and utilizing relevant characterization techniques will enable more precise MOF selection for specific applications.

Preparation of Cu/Sn-Organic Nano-Composite Catalysts for Potential Use in Hydrogen Evolution Reaction and Electrochemical Characterization

In this work, the solvothermal solidification method has been used to be prepared as a homogenous CuSn-organic nano-composite (CuSn-OC) to use as a catalyst for alkaline water electrolysis for cost-effective H2 generation. FT-IR, XRD, and SEM techniques were used to characterize the CuSn-OC which confirmed the formation of CuSn-OC with a terephthalic acid linker as well as Cu-OC and Sn-OC. The electrochemical investigation of CuSn-OC onto a glassy carbon electrode (GCE) was evaluated using the cyclic voltammetry (CV) method in 0.1 M KOH at room temperature. The thermal stability was examined using TGA methods, and the Cu-OC recorded a 91.4% weight loss after 800 °C whereas the Sn-OC and CuSn-OC recorded 16.5 and 62.4%, respectively. The results of the electroactive surface area (ECSA) were 0.5, 0.42, and 0.33 m2 g-1 for the CuSn-OC, Cu-OC, and Sn-OC, respectively, and the onset potentials for HER were -420, -900, and -430 mV vs. the RHE for the Cu-OC, Sn-OC, and CuSn-OC, respectively. LSV was used to evaluate the electrode kinetics, and the Tafel slope for the bimetallic catalyst CuSn-OC was 190 mV dec-1, which was less than for both the monometallic catalysts, Cu-OC and Sn-OC, while the overpotential was -0.7 vs. the RHE at a current density of -10 mA cm-2.

An electrochemiluminescence aptasensor based on highly luminescent silver-based MOF and biotin-streptavidin system for mercury ion detection

In this study, for the first time, a silver-based metal-organic framework (Ag-MOF) was synthesized and used as the electrochemiluminescence (ECL) emitter for building an ECL sensor. After modification with chitosan (CS) and gold nanoparticles (Au NPs), the ECL stability of Ag-MOF was improved. To detect mercury ions, a biosensor was constructed using the mercury ion aptamer and steric effect of streptavidin. First, the capture strand (cDNA) with terminal-modified sulfhydryl group was attached to the electrode surface by the Au-S bond. Then, the mercury-ion aptamer (Apt-Hg) modified with biotin was anchored to the electrode by complementary pairing with cDNA. Streptavidin (SA) could be fixed on the electrode by linking with biotin, thereby reducing the ECL signal. However, in the presence of mercury ions, the aptamer was removed and streptavidin could not be immobilized on the electrode. Hence, the ECL signal of the sensor increased with the concentration of mercury ions, which was linear in the range from 1 μM to 300 fM. The detection limit could reach 66 fM (S/N = 3). The sensor provided a new method for the detection of mercury ions.

A Modified Hydrolysis Method of Decolorizing Reactive-Dyed Polycotton Waste Fabric and Extraction of Terephthalic Acid: A Perspective to Reduce Textile Solid Waste

To manage the polycotton textile-waste fabric (PCWF), a modified alkaline hydrolysis method is used for decolorization and separation of polyester as terephthalic acid (TPA). The effects of optimum conditions on TPA yield (%) have been determined to be $97.66\pm 1.94\%$ . Dye degradations and K/S values are measured by UV-visible spectrophotometer. K/S value of PCWF is 37.06 and separated cotton fabric (SCF) is 0.035, respectively. The chemical functionalities and crystallinity of PCWF, SCF, and TPA are determined by using FTIR and XRD. FTIR peak values are 1684 cm-1, 1574 cm-1, 1512 cm-1, 1280 cm-1, and 1425 cm-1 that prove transformation of polyester to TPA. XRD peaks confirm polyester conversion to TPA, and the values are 17.4, 25.13, 28.12, 29.09, and 38.7. TGA, SEM, and EDX data showed the thermal stability, morphology, and elemental composition of TPA.

Ultrafast, Stable Electrochromics Enabled by Hierarchical Assembly of V2O5@C Microrod Network

Vanadium pentoxide (V₂O₅) with multicolor transition is widely studied in the electrochromic (EC) field to enrich color species of transition-metal oxides; yet, it always suffers from slow switching speed caused by poor electron conductivity and slow ion diffusion, poor cycling stability induced by large volume change during the EC reaction process. Herein, hierarchical network assembly of V₂O₅@C microrods is introduced to develop an ultrafast, stable, multicolor EC film. Using a two-step pyrolysis that involves metal-organic framework templates, porous microrods with a well-preserved one-dimensional structure are prepared through the assembly of V₂O₅@C nanocrystals at nanoscale, providing more active sites for ionic insertion and accessible pathways for electron transport. After spray-coating the V₂O₅@C microrods on conductive substrates, interconnected networks composed of V₂O₅@C microrods at microscale ensures the infiltration of electrolyte and provide ion transport channels. In addition, the nanoscale porous structure and coated carbon layer can accommodate volumetric changes during ion insertion/extraction process, ensuring high electrochemical stability. As a result, EC electrode with V₂O₅@C microrods network performed rapid switching speed (1.1/1.0 s) and stable cycle ability (96% after 2000 cycles). At last, flexible large-scale devices and multicolor digital displays were assembled to demonstrate potential application in next-generation wearable electronics.

Carbazole-Equipped Metal-Organic Framework for Stability, Photocatalysis, and Fluorescence Detection

The useful yet underutilized backfolded design is invoked here for functionalizing porous solids with the versatile carbazole function. Specifically, we attach carbazole groups as backfolded side arms onto the backbone of a linear dicarboxyl linker molecule. The bulky carbazole side arms point away from the carboxyl links and do not disrupt the Zr-carboxyl framework formation; namely, the resultant MOF solid ZrL1 features the same net as that of the unfunctionalized dicarboxyl linker, also known as the PCN-111 net or UiO-66 net. The ZrL1 structure features only half linker occupancy (about 6 out of the 12 linkers around the Zr₆O₈ cluster being missing) and partially collapses upon activation (acetone exchange and evacuation). Notably, the stability improves after heating in diphenyl oxide at 260 °C (POP-260 treatment; to form ZrL1-260), as indicated by the higher crystallinity and surface area of the activated ZrL1-260 sample. The ZrL1-260 samples achieve 72% yield in photocatalyzing reductive dehalogenation of phenacyl bromide; ZrL1 can detect nitro-aromatic compounds via fluorescence quenching, with selectivity and sensitivity toward 4-nitroaniline, featuring a limit of detection of 96 ppb.

New Validated Method for the Determination of Six Opium Alkaloids in Poppy Seed-Containing Bakery Products by High-Performance Liquid Chromatography-Tandem Mass Spectrometry after Magnetic Solid-Phase Extraction

Bakery products containing poppy seeds are increasingly being commercialized. These seeds may be contaminated with latex from the Papaver somniferum L. plant rich in opium alkaloids (OAs). Therefore, health authorities demand the development of analytical methods to control them. In this study, an efficient and simple method was developed and validated for the first time to analyze six OAs in bakery products by high-performance liquid chromatography-tandem mass spectrometry. For this purpose, a solid-liquid extraction was optimized, and then a magnetic material [magnetite surface-modified with Fe(III) terephthalate, denoted as Fe₃O₄@TPA-Fe] was used for a fast magnetic solid-phase extraction. The method has been validated with adequate recoveries (70-110%) and relative standard deviations (<20%) and without matrix effects. Nine bakery samples (five breadsticks and four sliced bread) were analyzed; breadsticks showed low amounts of OAs, but two sliced bread showed higher amounts of OAs than the new amount (1.5 mg/kg) set by the Commission Regulation (EU) 2021/2142.

Bioconversion of Terephthalic Acid and Ethylene Glycol Into Bacterial Cellulose by Komagataeibacter xylinus DSM 2004 and DSM 46604

Komagataeibacter xylinus strains DSM 2004 and DSM 46604 were evaluated for their ability to grow and produce bacterial cellulose (BC) upon cultivation on terephthalic acid (TA) and ethylene glycol (EG), which are monomers of the petrochemical-derived plastic polyethylene terephthalate (PET). Both strains were able to utilize TA, EG, and their mixtures for BC synthesis, with different performances. K. xylinus DSM 2004 achieved higher BC production from TA (0.81 ± 0.01 g/L), EG (0.64 ± 0.02 g/L), and TA + EG mixtures (0.6 ± 0.1 g/L) than strain DSM 46604. The latter was unable to utilize EG as the sole carbon source and reached a BC production of 0.16 ± 0.01 g/L and 0.23 ± 0.1 g/L from TA alone or TA + EG mixtures, respectively. Further supplementing the media with glucose enhanced BC production by both strains. During cultivation on media containing TA and EG, rapid pH drop due to metabolization of EG into acidic compounds led to some precipitation of TA that was impregnated into the BC pellicles. An adaptation of the downstream procedure involving BC dissolution in NaOH was used for the recovery of pure BC. The different medium composition tested, as well as the downstream procedure, impacted the BC pellicles’ physical properties. Although no variation in terms of the chemical structure were observed, differences in crystallinity degree and microstructure of the produced BC were observed. The BC produced by K. xylinus DSM 2004 had a higher crystallinity (19–64%) than that of the strain DSM 46604 (17–53%). Moreover, the scanning electron microscopy analysis showed a higher fiber diameter for K. xylinus DSM 2004 BC (46–56 nm) than for K. xylinus DSM 46604 (37–49 nm). Dissolution of BC in NaOH did not influence the chemical structure; however, it led to BC conversion from type I to type II, as well as a decrease in crystallinity. These results demonstrate that PET monomers, TA and EG, can be upcycled into a value-added product, BC, presenting an approach that will contribute to lessening the environmental burden caused by plastic disposal in the environment.

Reversible One- to Two- to Three-Dimensional Transformation in CuII Coordination Polymer

A reversible transformation between 1D, 2D, and 3D is demonstrated for the first time in coordination polymers comprising Cu^II ions and bidentate terephthalate (BDC^2- ). 1D uniform chains were reversibly transformed into 2D layers with the construction of Cu-paddlewheels by eliminating water molecules. 2D/3D reversible transformation was achieved by removing/rebinding N,N-dimethylformamide coordinated to the paddlewheels. These dimensional transformations significantly changed chemical and physical properties such as gas sorption and magnetism. Although the uptake in open-framework 1D and 2D Cu-BDC was insignificant, pronounced absorption was observed for 3D Cu-BDC. Drastic difference in magnetic behavior is consistent with their coordination structures; uniform 1D chain of Cu^II in 1D Cu-BDC and 2D sheet based on Cu^II -paddlewheel dimers in 2D Cu-BDC. Ferromagnetic behavior observed in air-exposed 3D Cu-BDC is attributed to the 3D structure formed by the connection of 2D sheets.

Further Insight into the Conversion of a Ni-Fe Metal-Organic Framework during Water-Oxidation Reaction

Metal-organic frameworks (MOFs) are extensively investigated as catalysts in the oxygen-evolution reaction (OER). A Ni-Fe MOF with 2,5-dihydroxy terephthalate as a linker has been claimed to be among the most efficient catalysts for the oxygen-evolution reaction (OER) under alkaline conditions. Herein, the MOF stability under the OER was reinvestigated by electrochemical methods, X-ray diffraction, X-ray absorption spectroscopy, energy-dispersive spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy, nuclear magnetic resonance, operando visible spectroscopy, electrospray ionization mass spectroscopy, and Raman spectroscopy. The peaks corresponding to the carboxylate group are observed at 1420 and 1520 cm^-1 using Raman spectroscopy. The peaks disappear after the reaction, suggesting the removal of the carboxylate group. A drop in carbon content but growth in oxygen content after the OER was detected by energy-dispersive spectra. This shows that after the OER, the surface of MOF is oxidized. SEM images also show deep restructures in the surface morphology of this Ni-Fe MOF after the OER. Nuclear magnetic resonance and electrospray ionization mass spectrometry show the decomposition of the linker in alkaline conditions and even in the absence of potential. These experimental data indicate that during the OER, the synthesized MOF transforms to a Fe-Ni-layered double hydroxide, and the formed metal oxide is a candidate for the OER catalysis. Generalization is not true; however, taken together, these findings suggest that the stability of Ni-Fe MOFs under harsh oxidation conditions should be reconsidered.

From Operando Raman Mechanochemistry to "NMR Crystallography": Understanding the Structures and Interconversion of Zn-Terephthalate Networks Using Selective 17O-Labeling

The description of the formation, structure, and reactivity of coordination networks and metal-organic frameworks (MOFs) remains a real challenge in a number of cases. This is notably true for compounds composed of Zn2+ ions and terephthalate ligands (benzene-1,4-dicarboxylate, BDC) because of the difficulties in isolating them as pure phases and/or because of the presence of structural defects. Here, using mechanochemistry in combination with operando Raman spectroscopy, the observation of the formation of various zinc terephthalate compounds was rendered possible, allowing the distinction and isolation of three intermediates during the ball-milling synthesis of Zn3(OH)4(BDC). An "NMR crystallography" approach was then used, combining solid-state NMR (1H, 13C, and 17O) and density functional theory (DFT) calculations to refine the poorly described crystallographic structures of these phases. Particularly noteworthy are the high-resolution 17O NMR analyses, which were made possible in a highly efficient and cost-effective way, thanks to the selective 17O-enrichment of either hydroxyl or terephthalate groups by ball-milling. This allowed the presence of defect sites to be identified for the first time in one of the phases, and the nature of the H-bonding network of the hydroxyls to be established in another. Lastly, the possibility of using deuterated precursors (e.g., D2O and d 4-BDC) during ball-milling is also introduced as a means for observing specific transformations during operando Raman spectroscopy studies, which would not have been possible with hydrogenated equivalents. Overall, the synthetic and spectroscopic approaches developed herein are expected to push forward the understanding of the structure and reactivity of other complex coordination networks and MOFs.

Capture of Gaseous Iodine in Isoreticular Zirconium-Based UiO-n Metal-Organic Frameworks: Influence of Amino Functionalization, DFT Calculations, Raman and EPR Spectroscopic Investigation

A series of Zr-based UiO-n MOF materials (n=66, 67, 68) have been studied for iodine capture. Gaseous iodine adsorption was collected kinetically from a home-made set-up allowing the continuous measurement of iodine content trapped within UiO-n compounds, with organic functionalities (-H, -CH₃ , -Cl, -Br, -(OH)₂ , -NO₂ , -NH₂ , (-NH₂ )₂ , -CH₂ NH₂ ) by in-situ UV-Vis spectroscopy. This study emphasizes the role of the amino groups attached to the aromatic rings of the ligands connecting the {Zr₆ O₄ (OH)₄ } brick. In particular, the preferential interaction of iodine with lone-pair groups, such as amino functions, has been experimentally observed and is also based on DFT calculations. Indeed, higher iodine contents were systematically measured for amino-functionalized UiO-66 or UiO-67, compared to the pristine material (up to 1211 mg/g for UiO-67-(NH₂ )₂ ). However, DFT calculations revealed the highest computed interaction energies for alkylamine groups (-CH₂ NH₂ ) in UiO-67 (-128.5 kJ/mol for the octahedral cavity), and pointed out the influence of this specific functionality compared with that of an aromatic amine. The encapsulation of iodine within the pore system of UiO-n materials and their amino-derivatives has been analyzed by UV-Vis and Raman spectroscopy. We showed that a systematic conversion of molecular iodine (I₂ ) species into anionic I^- ones, stabilized as I^- ⋅⋅⋅I₂ or I₃ ^- complexes within the MOF cavities, occurs when I₂ @UiO-n samples are left in ambient light.

Photoactive Zr-aromatic hybrid thin films made by molecular layer deposition

The principle of antimicrobial photodynamic therapy (PDT) is appealing because it can be controlled by an external light source and possibly the use of durable materials. However, to utilise such surfaces requires a process for their production that allows for coating on even complex geometries. We have therefore explored the ability of the emerging molecular layer deposition (MLD) technique to produce and tune PDT active materials. This study demonstrates how the type of aromatic ligand influences the optical and antimicrobial properties of photoactive Zr-organic hybrid thin films made by MLD. The three aromatic dicarboxylic acids: 2,5-dihydroxy-1,4-benzenedicarboxylic acid, 2-amino-1,4-benzenedicarboxylic acid and 2,6-naphthalenedicarboxylic acid have been combined with ZrCl₄ to produce hybrid coatings. The first system has not been previously described by MLD and is therefore more thoroughly investigated using in situ quartz crystal microbalance (QCM), Fourier transform infrared (FTIR) and UV-Vis spectroscopy. The antibacterial phototoxic effects of Zr-organic hybrids have been explored in the Staphylococcus aureus bacteria model using a UVA/blue light source. Films based on the 2,6-naphthalenedicarboxylic acid linker significantly reduced the number of viable bacteria by 99.9%, while no apparent activity was observed for the two other photoactive systems. Our work thus provides evidence that the MLD technique is a suitable tool to produce high-quality novel materials for possible applications in antimicrobial PDT, however it requires a careful selection of aromatic ligands used to construct photoactive materials.

Photoactive organic–inorganic hybrid thin films for potential use in antimicrobial photodynamic therapy (PDT) were fabricated based on Zr clusters and three different aromatic dicarboxylic acid linkers using the molecular layer deposition (MLD) technique.

Atomic / Molecular Layer Deposition of Cerium (III) Hybrid Thin Films using Rigid Organic Precursors

Atomic / molecular layer deposition (ALD/MLD) process for the fabrication of cerium-based metal-organic hybrid films is demonstrated for the first time. The highly reactive cerium (III) guanidinate precursor [Ce(dpdmg)3] was...

Surface-Adsorbed Carboxylate Ligands on Layered Double Hydroxides/Metal-Organic Frameworks Promote the Electrocatalytic Oxygen Evolution Reaction

Metal-organic frameworks (MOFs) with carboxylate ligands as co-catalysts are very efficient for the oxygen evolution reaction (OER). However, the role of local adsorbed carboxylate ligands around the in-situ-transformed metal (oxy)hydroxides during OER is often overlooked. We reveal the extraordinary role and mechanism of surface-adsorbed carboxylate ligands on bi/trimetallic layered double hydroxides (LDHs)/MOFs for OER electrocatalytic activity enhancement. The results of X-ray photoelectron spectroscopy (XPS), synchrotron X-ray absorption spectroscopy, and density functional theory (DFT) calculations show that the carboxylic groups around metal (oxy)hydroxides can efficiently induce interfacial electron redistribution, facilitate an abundant high-valence state of nickel species with a partially distorted octahedral structure, and optimize the d-band center together with the beneficial Gibbs free energy of the intermediate. Furthermore, the results of in situ Raman and FTIR spectra reveal that the surface-adsorbed carboxylate ligands as Lewis base can promote sluggish OER kinetics by accelerating proton transfer and facilitating adsorption, activation, and dissociation of hydroxyl ions (OH^- ).

Facile and Fast Transformation of Nonluminescent to Highly Luminescent Metal-Organic Frameworks: Acetone Sensing for Diabetes Diagnosis and Lead Capture from Polluted Water

Metal-organic frameworks (MOFs) stand as one of the most promising materials for the development of advanced technologies owing to their unique combination of properties. The conventional synthesis of MOFs involves a direct reaction of the organic linkers and metal salts; however, their postsynthetic modification is a sophisticated route to produce new materials or to confer novel properties that cannot be attained through the traditional methods. This work describes the postsynthetic MOF-to-MOF transformation of a nonluminescent MOF (Zn-based Oxford University-1 material [Zn-BDC, where BDC = 1,4-benzene dicarboxylate] (OX-1)) into a highly luminescent framework (Ag-based Oxford University-2 material [Ag-BDC] (OX-2)) by a simple immersion of the former in a silver salt solution. The conversion mechanism exploits the uncoordinated oxygen atoms of terephthalate linkers found in OX-1, instead of the unsaturated metal sites commonly employed, making the reaction much faster. The materials derived from the OX-1 to OX-2 transformation are highly luminescent and exhibit a selective response to acetone, turning them into a promising candidate for manufacturing fluorometric sensors for the diagnosis and monitoring of diabetes mellitus. Our methodology can be extended to other metals such as lead (Pb). The fabrication of a polymer mixed-matrix membrane containing OX-1 is used as a proof-of-concept for capturing Pb ions (as pollutants) from water. This research instigates the exploration of alternative methodologies to confer MOFs with special aptitudes for photochemical sensing or for environmental applications such as water purification.

Plasmonic metal-organic framework nanocomposites enabled by degenerately doped molybdenum oxides

Metal-organic frameworks (MOFs) nanocomposites are under the limelight due to their unique electronic, optical, and surface properties for various applications. Plasmonic MOFs enabled by noble metal nanostructures are an emerging class of MOF nanocomposites with efficient solar light-harvesting capability. However, major concerns such as poor photostability, sophisticated synthesis processes, and high fabrication cost are raised. Here, we develop a novel plasmonic MOF nanocomposite consisting of the ultra-thin degenerately doped molybdenum oxide core and the flexible iron MOF (FeMOF) shell through a hydrothermal growth, featuring low cost, facile synthesis, and non-toxicity. More importantly, the incorporation of plasmonic oxides in the highly porous MOF structure enhances the visible light absorbability, demonstrating improved photobleaching performances of various azo and non-azo dyes compared to that of pure FeMOF without the incorporation of oxidative agents. Furthermore, the nanocomposite exhibits enhanced sensitivity and selectivity towards NO₂ gas at room temperature, attributed to the electron-rich surface of plasmonic oxides. This work possibly broadens the exploration of plasmonic MOF nanocomposites for practical and efficient solar energy harvesting, environmental remediation, and environmental monitoring applications.

Ultrathin Mn Doped Ni-MOF Nanosheet Array for Highly Capacitive and Stable Asymmetric Supercapacitor

In this study, we demonstrate that an Mn-doped ultrathin Ni-MOF nanosheet array on nickel foam (Mn_0.1 -Ni-MOF/NF) serves as a highly capacitive and stable supercapacitor positive electrode. The Mn_0.1 -Ni-MOF/NF shows an areal capacity of 6.48 C cm^-2 (specific capacity C: 1178 C g^-1 ) at 2 mA cm^-2 in 6.0 m KOH, outperforming most reported MOF-based materials. More importantly, it possesses excellent cycle stability to maintain 80.6 % capacity after 5000 cycles. An asymmetric supercapacitor device utilizing Mn_0.1 -Ni-MOF/NF as the positive electrode and activated carbon as the negative electrode attains a high energy density of 39.6 Wh kg^-1 at 143.8 Wkg^-1 power density with a capacitance retention of 83.6 % after 5000 cycles.

Cobalt-carbon/silica nanocomposites prepared by pyrolysis of a cobalt 2,2'-bipyridine terephthalate complex for remediation of cationic dyes

Recently, carbon nanostructures have attracted interest because of their unique properties and interesting applications. Here, CoC@SiO₂-850 (3) and CoC@SiO₂-600 (4) cobalt–carbon/silica nanocomposites were prepared by solid-state pyrolysis of anthracene with Co(tph)(2,2′-bipy)·4H₂O (1) complex in the presence of silica at 850 and 600 °C, respectively, where 2,2′-bipy is 2,2′-bipyridine and tph is the terephthalate dianion. Moreover, Co(μ-tph)(2,2′-bipy) (2) was isolated and its X-ray structure indicated that cobalt(ii) has a distorted trigonal prismatic coordination geometry. 2 is a metal–organic framework consisting of one-dimensional zigzag chains within a porous grid network. 3 and 4 consist of cobalt(0)/cobalt oxide nanoparticles with a graphitic shell and carbon nanotubes embedded in the silica matrix. They were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), powder X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). XPS revealed that the nanocomposites are functionalized with oxygen-containing groups, such as carboxylic acid groups. In addition, the presence of metallic cobalt nanoparticles embedded in graphitized carbon was verified by XRD and TEM. The efficiency of 3 for adsorption of crystal violet (CV) dye was investigated by batch and column experiments. At 25 °C, the Langmuir adsorption capacity of 3 for CV was 214.2 mg g⁻¹ and the fixed-bed column capacity was 36.3 mg g⁻¹. The adsorption data were well fitted by the Freundlich isotherm and pseudo-second-order kinetic model. The adsorption process was spontaneous and endothermic.

A cobalt–carbon@silica nanocomposite was synthesized from a cobalt 2,2′-bipyridine terephthalate complex and its adsorption behavior towards crystal violet dye was tested using batch and column techniques.

Amorphous-to-crystalline transition and photoluminescence switching in guest-absorbing metal–organic network thin films

Amorphous-to-crystalline (aMOF-to-MOF) transition and simultaneous quenching of luminescence are seen upon water absorption for Nd-terephthalate thin films grown using ALD/MLD method.

Investigation of Potential Amorphisation and Co-Amorphisation Behaviour of the Benzene Di-Carboxylic Acids upon Cryo-Milling

Multi-component formulations offer a way to modulate the physico-chemical properties of drug molecules and thereby enhance their efficacy as medicines compared to using only the raw drug, with mechano-chemical synthesis being an increasingly popular way to create these novel materials in a research setting. However, to date studies have focussed on employing pharmaceutically acceptable components, which has led to the literature featuring chemically diverse pairings of drug and excipient. Here we investigate the outcome of cryo-milling and co-cryo-milling of a series of three simple geometrical isomers of benzene di-carboxylic acid with a view to developing a chemically simple model system to investigate areas including cryo-milling, co-cryo-milling, co-amorphous formulation, etc. All three single-component materials exhibit differing behaviour upon cryo-milling and subsequent storage, as do the two-component mixtures. The surprisingly differing behaviours of these chemically similar species upon cryo-milling and co-cryo-milling suggest that molecular chemistry may not be the dominant influence on the outcome of mechano-chemical syntheses, and that other properties should be explored to develop a predictive model for the outcomes of these types of reactions.

From Molecular Fragments to the Bulk: Development of a Neural Network Potential for MOF-5

The development of first-principles-quality reactive atomistic potentials for organic-inorganic hybrid materials is still a substantial challenge because of the very different physics of the atomic interactions-from covalent via ionic bonding to dispersion-that have to be described in an accurate and balanced way. In this work we used a prototypical metal-organic framework, MOF-5, as a benchmark case to investigate the applicability of high-dimensional neural network potentials (HDNNPs) to this class of materials. In HDNNPs, which belong to the class of machine learning potentials, the energy is constructed as a sum of environment-dependent atomic energy contributions. We demonstrate that by the use of this approach it is possible to obtain a high-quality potential for the periodic MOF-5 crystal using density functional theory (DFT) reference calculations of small molecular fragments only. The resulting HDNNP, which has a root-mean-square error (RMSE) of 1.6 meV/atom for the energies of molecular fragments not included in the training set, is able to provide the equilibrium lattice constant of the bulk MOF-5 structure with an error of about 0.1% relative to DFT, and also, the negative thermal expansion behavior is accurately predicted. The total energy RMSE of periodic structures that are completely absent in the training set is about 6.5 meV/atom, with errors on the order of 2 meV/atom for energy differences. We show that in contrast to energy differences, achieving a high accuracy for total energies requires careful variation of the stoichiometries of the training structures to avoid energy offsets, as atomic energies are not physical observables. The forces, which have RMSEs of about 94 meV/ a₀ for the molecular fragments and 130 meV/ a₀ for bulk structures not included in the training set, are insensitive to such offsets. Therefore, forces, which are the relevant properties for molecular dynamics simulations, provide a realistic estimate of the accuracy of atomistic potentials.

Experimental, DFT dimeric modeling and AIM study of H-bond-mediated composite vibrational structure of Chelidonic acid

The composite vibrational structure near 3650–3200 and 3000–2400 cm⁻¹ in the observed IR absorption spectrum of Chelidonic acid has been explained in terms of intra- and inter-molecular −O−H∙∙∙O H-bonding attributed to monomer and dimer species computed at B3LYP/6–311++G(d,p) level. Three of the six dimer species derived out of ten monomeric components have shown both intra- and inter-molecular H-bonding. Vibrational modes of the monomer and dimer species are satisfactorily identified with the observed IR and Raman bands including frequency shifts associated with the H-bondings. The H-bond interactions in the monomer and dimer species have been characterized in terms of electron density, ρ(r), its Laplacian, ∇²ρ(r) and potential energy density at the O∙∙∙H bond critical points (BCPs) based on the Atoms in Molecules (AIM) theory. The attractive (van der Waals, H-bonds) and repulsive steric clash (SC) interactions are explained using computed reduced density gradient values from the noncovalent interaction (NCI) method. The AIM analysis confirms the presence of the intra- and inter-molecular H-bondings in the monomer/dimer species. The natural bond orbital (NBO) analysis of the natural charges and stabilization energy of the H-bonds for the dimer species further points to the stronger inter-than intra-molecular H-bonding.

3D Macroporous Zinc Compound/Silicone Hybrid Foams for Amperometric Sensing of Glucose Oxidase

A 3D porous matrix makes an intriguing sensing platform, which can integrate functional guest molecules. Here, the first demonstration of a zinc compound/silicone hybrid foam is reported for amperometric sensing of glucose oxidase. The silicone foam is fabricated by a self-developed solid-filling-melting method. Two zinc-based polymers, Zn-Compound-1 and Zn-Compound-2, are synthesized. Zn-Compound-1 and Zn-Compound-2 are characterized by X-ray diffraction, X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, Raman spectroscopy, and X-ray absorption nearedge structure spectroscopy of carbon K-edge, oxygen K-edge, and zinc L-edge. Effective amperometric sensing of glucose oxidase is achieved by introducing Zn-Compound-1 or Zn-Compound-2 into the silicone foam, i.e., an increase of the concentration of the glucose oxidase led to an increase of detected current. This phenomenon can be explained by a possible mechanism of the formation of electron extra bands.

The physicochemical investigation of hydrothermally reduced textile waste and application within carbon-based electrodes

Textile waste is on the rise due to the expanding global population and the fast fashion market. Large volumes of textile waste are increasing the need for new methods for recycling mixed fabric materials. This paper employs a hydrothermal conversion route for a polyester/cotton mix in phosphoric acid to generate carbon materials (hydrochars) for electrochemical applications. A combination of characterization techniques revealed the reaction products were largely comprised of two major components. The first is a granular material with a surface C : O ratio of 2 : 1 interspersed with phosphorous and titanium proved using energy dispersive X-ray spectroscopy, and the other is a crystalline material with a surface C : O ratio of 3 : 2 containing no phosphorous or titanium. The latter material was found via X-ray diffraction and differential scanning calorimetry to be terephthalic acid. Electrochemical experiments conducted using the hydrochar as a carbon paste electrode demonstrates an increase in current response compared to carbon reference materials. The improved current responses, intrinsically related to the surface area of the material, could be beneficial for electrochemical sensor applications, meaning that this route holds promise for the development of a cheap recycled carbon material, using straightforward methods and simple laboratory reagents.

A novel method for chemically processing blended textiles is investigated, revealing a conductive carbon material as a major product.

Nickel–copper bimetal organic framework nanosheets as a highly efficient catalyst for oxygen evolution reaction in alkaline media

NiCu MOF nanosheets on Ni foam (NiCu-MOFNs/NF) exhibit superior catalytic OER performance, needing an overpotential of 309 mV at 100 mA cm⁻² in 1.0 M KOH.

Synergistic chemo-enzymatic hydrolysis of poly(ethylene terephthalate) from textile waste

Due to the rising global environment protection awareness, recycling strategies that comply with the circular economy principles are needed. Polyesters are among the most used materials in the textile industry; therefore, achieving a complete poly(ethylene terephthalate) (PET) hydrolysis in an environmentally friendly way is a current challenge. In this work, a chemo‐enzymatic treatment was developed to recover the PET building blocks, namely terephthalic acid (TA) and ethylene glycol. To monitor the monomer and oligomer content in solid samples, a Fourier‐transformed Raman method was successfully developed. A shift of the free carboxylic groups (1632 cm⁻¹) of TA into the deprotonated state (1604 and 1398 cm⁻¹) was observed and bands at 1728 and 1398 cm⁻¹ were used to assess purity of TA after the chemo‐enzymatic PET hydrolysis. The chemical treatment, performed under neutral conditions (T = 250 °C, P = 40 bar), led to conversion of PET into 85% TA and small oligomers. The latter were hydrolysed in a second step using the Humicola insolens cutinase (HiC) yielding 97% pure TA, therefore comparable with the commercial synthesis‐grade TA (98%).