Search Results (37)

A series of novel heterometallic rare-earth chloroterephthalate metal–organic frameworks with the general formula (Tb_xGd_1−x)₂(Cl-1,4-bdc)₃·5H₂O (x = 0–1) were synthesized via direct precipitation from aqueous solutions. The structural and photophysical properties of these compounds were studied in detail. All compounds exhibit bright luminescence upon UV excitation into the ligand absorption band due to an efficient antenna effect. The photoluminescence quantum yield shows a non-monotonic dependence on the concentration of the terbium ion with a maximum value of 71% achieved for the compound containing equal molar fractions of the lanthanide ions. The (Tb_0.5Gd_0.5)₂(Cl-1,4-bdc)₃·5H₂O sample was evaluatedfor its utility in both qualitative and quantitative analysis of selected metal ions and in latent fingerprint development. It was shown to enable the detection of Cr(III), Fe(III), and Cu(II) ions through luminescence quenching, with the emission intensity being concentration-dependent. This behaviour highlights the compound’s potential as a basis for analytical protocols and materials aimed at the quantitative determination of these metal ions. Full article

Copper oxide (CuO) is a narrow-bandgap p-type semiconductor promising for visible-light photocatalysis, yet it suffers from rapid charge recombination and low carrier transfer efficiency. In this study, two distinct CuO photocatalysts were fabricated via different routes: two-dimensional CuO nanosheets derived from annealing a CuBDC metal–organic framework (MOF) precursor, and oriented one-dimensional CuO nanoflower arrays prepared by electrochemical deposition, followed by annealing. The crystal structure, morphology, optical absorption, and photoelectrochemical properties were systematically characterized by XRD, SEM, XPS, UV-Vis spectroscopy, transient photocurrent response, EIS, and PL spectroscopy. The CuO nanoflower thin film exhibits a broad visible-light absorption, a markedly higher photocurrent density (42.25 μA cm⁻²), and lower charge-transfer resistance compared to CuO nanosheets. When evaluated for visible-light photocatalytic degradation of methylene blue (MB), rhodamine B (RhB), and malachite green (MG), the CuO thin film completely degraded MB within 15 min, with an apparent rate constant of 20.15 h⁻¹—approximately three times that of CuO nanosheets. It also showed 1.2- and 1.28-fold higher activity for RhB and MG, respectively. The enhanced performance is attributed to the oriented nanoflower architecture that provides continuous charge transport pathways, suppresses carrier recombination, and extends light propagation via multiple reflections. This work demonstrates that microstructural engineering is an effective strategy to overcome the intrinsic limitations of CuO photocatalysts for wastewater treatment. Full article

The electrocatalytic reduction in N₂ and CO₂ into urea under ambient conditions provides a promising strategy for sustainable nitrogen fixation and carbon utilization. However, the low activity and poor selectivity toward urea limit its practical application. Herein, a dual-ligand Cu-based metal–organic framework (Cu-BTC/NH₂BDC) was constructed via ligand engineering strategy. The introduction of 2-NH₂BDC modulated the electronic structure of Cu sites, generating electron-enriched Cu centers that facilitate CO₂ activation, while the hydrogen bonding interaction between the amino and carboxyl groups promotes the activation of N₂. As a result, the optimized Cu-BTC/NH₂BDC catalyst achieved a urea yield of 6.59 mmol g⁻¹ h⁻¹ with a Faradaic efficiency of 22.85% at −0.2 V versus reversible hydrogen electrode (vs. RHE), outperforming single-ligand counterparts. In situ Raman spectroscopy measurement revealed enhanced the formation of *CO, *NN, and C-N intermediates, indicating improved C-N coupling efficiency. This work provides a feasible strategy for regulating active sites in MOF-based catalysts toward efficient urea electrosynthesis. Full article

Synthesis of anionic metal–organic framework Na[Ce(BDC)₂(DMF)₂] based on cerium (III)–sodium terephthalate was performed. The crystal structure, studied by the Rietveld method, consists of anionic [Ce(BDC)₂]⁻ layers, connected by interlayer sodium cations in a 3D network. Variable-temperature PXRD, total X-ray scattering with pair distribution function analysis, and DFT calculations revealed framework structure stability upon DMF elimination and thermal treatment up to 300 °C. Modification with copper cations was performed using wetness impregnation with a Cu(NO₃)₂ methanol solution to obtain a catalyst for carbon monoxide oxidation. Cu²⁺@Na[Ce(BDC)₂(DMF)₂] in situ decomposition leads to the catalytic activity of the resulting CuO/CeO₂ composite during CO gas oxidation by air. Full article

Reactions of the angular 4,4′-oxybis[N-(pyridin-3-ylmethyl)benzamide] (L) with dicarboxylic acids and transition metal salts afforded non-entangled {[Cd(L)(1,3-BDC)(H₂O)]∙2H₂O}_n (1,3-BDC = 1,3-benzenedicarboxylic acid), 1; {[Cd(L)(1,4-HBDC)(1,4-BDC)_0.5]∙2H₂O}_n (1,4-BDC = 1,4-benzenedicarboxylic acid), 2; {[Cu₂(L)₂(1,3-BDC)₂]∙1.5H₂O}_n, 3; {[Ni(L)(1,3-BDC)(H₂O)]∙2H₂O}_n, 4; {[Zn(L)(1,3-BDC)]∙4H₂O}_n, 5; {[Zn(L)(1,4-BDC)]∙2H₂O}_n, 6; and [Cd₃(L)₂(1,4-BDC)₃]_n, 7, which have been structurally characterized by using single-crystal X-ray diffraction. Complexes 1–5 and 7 are 2D layers, giving (6⁴·8·10)(6)-2,4L3, (4²·8²·10²)(4²·8⁴)₂(4)₂, (4·5·6)(4·5⁵·6³·7)-3,5L66, (6⁴·8·10)(6)-2,4L3, interdigitated (8⁴·12²)(8)₂-2,4L2 and (3⁶·4⁶·5³)-hxl topologies, respectively, and 6 is a 1D chain with the (4³·6²·8)(4)-2,4C3 topology. The factors that govern the structures of 1–7 are discussed and the thermal properties of 1–7 and the luminescent properties of complexes 1, 2, 5 and 6 are investigated. The stabilities of complexes 1 and 5 toward the detection of Fe³⁺ ions are also evaluated. Full article

Multimode immunoassays based on multiple response mechanisms have received great attention due to their capacity to effectively improve the accuracy and reliability of biosensing platforms. However, few strategies have been reported for triple-mode immunoassays due to the shortage of multifunctional sensing materials and the incompatibility of signal transduction methods in different detection modes. In this work, a fluorescent–electrochemical–colorimetric triple-mode immunoassay platform was proposed with Cu-based metal–organic frameworks (MOFs) as the signal labels. The captured Cu-MOFs were successfully decomposed under an acidic condition, leading to the release of numerous Cu²⁺ ions and 2-aminobenzene-1,4-dicarboxylic acid (NH₂-BDC) ligands. The released NH₂-BDC were determined by fluorescence titration. Meanwhile, the released Cu²⁺ were readily quantified by differential pulse voltammetry (DPV) and simply detected through the catalytic oxidation of chromogenic substrate 3,3′,5,5′-tetramethylbenzidine (TMB). Taking alpha-fetoprotein (AFP) as a model analyte, the designed triple-mode immunoassays showed good performances with the linear range of 10–200 pg/mL, 10–200 pg/mL, and 1–100 pg/mL for the fluorescent, electrochemical, and colorimetric modes, respectively. The proposed triple-mode biosensing platforms show great potential for the applications in disease diagnosis, since they can be easily extended to other bioassays by changing the targets and recognition elements. Full article

The reaction of copper nitrate, phthalic acid (1,2-H₂BDC), and bipyridine in ammonia/ethanol media affords two multi-copper (II) cluster-based coordination polymers, namely {[Cu₄(bpy)₄(OH)₂(BDC)₂]·2OH·13H₂O}_n (USC-CP-6) and {[Cu₂(BDC)₂(bpy)₂(H₂O)]·3H₂O}_n (USC-CP-7), under ambient conditions, with CP-6 forming at the bottom and CP-7 at the upper edge of the same beaker. The single-crystal structures reveal that it is a rare case of gradient-induced formation of different multi-copper(II) cluster-based CPs within a single-solution chemical reaction. CP-6 crystallizes in the monoclinic system, sp. gr. P2₁/c, and is composed of chair-like tetranuclear [Cu₄(μ₃-OH)₂(bpy)₄(BDC)₂]²⁺ clusters as secondary building units, bridged by BDC²⁻ ligands to form a two-dimensional layer framework, while CP-7 crystallizes in the monoclinic system, sp. gr. P2₁/n, with binuclear [Cu₂(1,2-BDC)₂(bpy)₂(H₂O)] clusters linked by bridging BDC²⁻ ligands to form a one-dimensional looped double chain. Through intermolecular π–π stacking and hydrogen bonds between the coordination water, lattice water, and free oxygen atoms from carboxylate, both compounds yield a 3D supramolecular structure. Full article

Asthma and allergic rhinitis (AR) stand as prevalent chronic ailments impacting children within the United States. It is approximated that as many as 40% of American children exhibit symptoms indicative of AR, a condition which, if inadequately managed, could potentially lead to the onset of additional illnesses such as asthma, rhinosinusitis, allergic conjunctivitis, and otitis media. We have devised a universal synthetic pathway to encapsulate small molecules of montelukast sodium within Metal–Organic Frameworks (MOFs) for the treatment of asthma and AR. Two distinct Cu-MOFs, namely single linker and mixed linker MOFs, were synthesized through the solvothermal method utilizing 1,4-benzenedioic acid (BDC) and 4,4′-dipyridile as linkers. The synthesized Cu-MOFs underwent thorough examination employing various analytical techniques including BET, SEM, FTIR, and PXRD. These MOFs hold promise as potential vehicles for drug delivery applications. Various proportions of Cu-MOF-1 and Cu-MOF-2 were dispersed alongside montelukast sodium. Notably, the 1:1 ratio of both MOFs exhibited enhanced drug absorption compared to other ratios. Furthermore, Cu-MOF-2 demonstrated superior drug absorption overall when contrasted with Cu-MOF-1. This investigation also delves into the drug release dynamics from different ratios of MOFs and the drug. The drug release analysis was conducted in a phosphate-buffered saline (PBS) solution with a pH of 7.4, and the absorbance values were measured using a UV-visible spectrometer at distinct time intervals. Drug molecules are effectively encapsulated within MOFs and demonstrate controlled release through the establishment of hydrogen bonding or π–π interactions between the drug molecules and MOFs. Despite notable advancements in the utilization of MOFs for biomedical purposes, additional enhancements are necessary before they can be considered viable therapeutic modalities. Full article

A novel porous metal-organic framework (MOF), pCu-BDC-NH₂, with hierarchical porosity was synthesized using cetyltrimethylammonium bromide (CTAB) as a pore-generation agent. In addition to its common functions including structure-directing ligands or soft micelle templates, the judicious use of CTAB effectively modulated pore architecture in Cu-BDC-NH₂ MOFs. With additional mesopores generated during the synthesis process, the intrinsic MOF scaffolds further obtained pore hierarchies and interconnectivity, enabling efficient substrate access to the active metal centers, and thus significantly facilitated catalytic performance. As a proof of concept, we applied the finely engineered porous MOF pCu-BDC-NH₂ in a cascaded enzymatic system for xanthine sensing. This colorimetric biosensor exhibited a low detection limit of 0.11 μM, and a wide linear range of 1–120 μM. Furthermore, the sensor demonstrated exceptional stability, reproducibility, and was independent of interferences. Our simple yet effective method may find broader applications in tailoring pore architecture, enabling finer engineered structures to improve catalytic activities of nanomaterials. Full article

Methane, a greenhouse gas with 21 times the global warming potential of carbon dioxide, is increasingly subject to stringent emission regulations, driving the demand for high-performance methane sensors. This study proposes a novel IR spectroscopy technique based on a CuBDC-integrated microcantilever (CuBDC-microcantilever IR spectroscopy) for CH₄ sensing, offering exceptional sensitivity and selectivity. The metal-organic framework (MOF) CuBDC was synthesized on the microcantilever using a drop-and-dry method facilitated by an intense pulsed light technique. Characterization via scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy confirmed the successful formation of CuBDC on the microcantilever. The CuBDC-microcantilever IR spectroscopy demonstrated a significantly enhanced sensitivity, with a differential amplitude at the CH₄ characteristic peak approximately 13 times higher than that of a conventional Si microcantilever. Moreover, the limit of detection was determined to be as low as 14.05 ppm. The clear separation of the CH₄ characteristic peak from the water and acetone vapor peaks also emphasized the sensor’s high selectivity. These findings highlight the superior sensitivity and selectivity of the proposed sensor, positioning it as a promising platform for CH₄ detection in industrial and environmental applications. Full article

A promising solution for efficient methane (CH₄) storage and transport is a metal–organic framework (MOF)-based sorbent. Hence, searching for potential MOFs like M₂(BDC)₂(DABCO) to enhance the CH₄ storage capacity in both gravimetric and volumetric uptakes is essential. Herein, we systematically elucidate the adsorption of CH₄ in M₂(BDC)₂(DABCO) or M(DABCO) (M = Mg, Mn, Fe, Co, Ni, Cu, Zn) MOFs using multiscale simulations that combined grand canonical Monte Carlo simulation with van der Waals density functional (vdW-DF) calculation. We find that, in the M(DABCO) series, Mg(DABCO) has the highest total CH₄ adsorption capacities, with $m_{tot}=$ 231.39 mg/g at 298 K, for gravimetric uptake, and $V_{tot}=$ 231.43 cc(STP)/cc, for volumetric uptake. The effects of temperature, pressure, and metal substitution on enhancing CH₄ storage are evaluated, and we predict that the volumetric CH₄ storage capacity on M(DABCO) could meet the DOE target at temperatures of ca. 238 K–268 K and pressures of 35–100 bar. The interactions between CH₄ and M(DABCO) are dominated by the vdW interactions, as shown by the vdW-DF calculations. The Mg, Mn, Fe, Co, and Ni substitutions in M(DABCO) result in a stronger interaction and thus, a higher CH₄ storage capacity, at higher pressures for Mg, Mn, Ni, and Co and at lower pressures for Fe. This work may provide guidance for the rational design of CH₄ storage in M₂(BDC)₂(DABCO) MOFs. Full article

CNT-NH₂-Cu-BTC was prepared via hydrothermal synthesis for the adsorption and separation of CO₂/CH₄ mixtures with 2, 6, and 10% multiwalled carbon nanotube (MWCNT) additions. NH₂-BTC composites were synthesized by changing the organic ligand and adding NH₂-BDC (15, 25, 35, and 45%) to improve the adsorption capacity. MWCNTS were loaded to enhance the water stability of the material. The structure, surface morphology, and pore size distribution of the composites were characterized using X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, and specific surface area and pore structure measurements. The CO₂/CH₄ selective adsorption performance was studied via breakthrough experiments using a self-made adsorption device. The CO₂ adsorption capacity of Cu-BTC increased due to the addition of NH₂-BDC, with 35%NH₂-Cu-BTC exhibiting the best CO₂ adsorption property, i.e., a CO₂ adsorption capacity of 1.82 mmol/g and a CO₂/CH₄ separation coefficient of 1.44 at 35 °C and 20 mL/min. After adding MWCNTs, 6%CNT-NH₂-Cu-BTC exhibited the best CO₂ adsorption property and water stability, with the CO₂ adsorption capacity increasing to 2.06 mmol/g. 6%CNT-NH₂-Cu-BTC with wet impregnation retained 79% of the CO₂ adsorption capacity of the sample without wet impregnation, demonstrating its excellent water stability under humid conditions. Cyclic experiments with and without wet impregnation were performed. Full article

Some copper-based metal–organic frameworks show promise for use as electrocatalysts because they allow for an electrode configuration in which copper species with redox and electron-conducting properties are immobilized in a three-dimensional arrangement. This work shows that the synthesis of copper terephthalates (Cu-BDCs) can lead to rigid structures of the copper hydroxyterephthalate-type or flexible structures that are isoreticular to the MOF-2 type, depending solely on the synthesis route. Here, a detailed analysis of the syntheses of the crystals is carried out employing protocols with different solvents as well as conventional or microwave-assisted solvothermal methods. All solids were fully characterized by a combination of characterization techniques, such as FE-SEM, T-XRD, TGA, and FTIR, and their electrochemical redox responses were also evaluated by cyclic voltammetry. A correlation between the Cu-BDCs structures and their electrochemical behaviors was established and a new version of an electroactive copper hydroxyterephthalate was synthesized by a microwave method in 3 h with a dimethylformamide-free protocol. This Cu-BDC was obtained as dispersed nanoflakes with a high amount of copper sites and the capacity to be reversibly electroreduced-oxidized and showed catalytic activity in the oxygen reduction reaction (ORR). Full article

Developing metal–organic framework (MOF) adsorbents with excellent performance and robust stability is of critical importance to reduce CO₂ emissions yet challenging. Herein, a robust ultra-microporous MOF, Cu(bpfb)(bdc), with mixed ligands of N, N′-(1,4-phenylene)diisonicotinamide (bpfb), and 1,4-dicarboxybenzene (bdc) was delicately constructed. Structurally, this material possesses double-interpenetrated frameworks formed by two staggered, independent frameworks, resulting in two types of narrow ultra-micropores of 3.4 × 5.0 and 4.2 × 12.8 Ų, respectively. The above structural properties make its highly selective separation at 273~298 K with a CO₂ capacity of 71.0~86.2 mg/g. Its adsorption heat over CO₂ and IAST selectivity were calculated to be 27 kJ/mol and 52.2, respectively. Remarkably, cyclic breakthrough experiments corroborate its impressive performance in CO₂/N₂ separation in not only dry but also 75% RH humid conditions. Molecular simulation reveals that C-H···O_CO2 in the pores plays a pivotal role in the high selectivity of CO₂ adsorption. These results point out the huge potential application of this material for CO₂/N₂ separation. Full article

Metal-organic frameworks (MOFs) have attracted considerable interest as emerging heterogeneous catalysts for organic transformations of synthetic utility. Herein, a Lewis-acidic MOF, {[Cu₃(PEIP)₂(5-NH₂-mBDC)(DMF)]·7DMF}∞, denoted as Cu(ΙΙ)-PEIP, has been synthesized via a one-pot process and deployed as an efficient heterogeneous catalyst for a Diels–Alder cycloaddition. Specifically, the [4 + 2] cycloaddition of 13 substituted azachalcone dienophiles with cyclopentadiene has been investigated. MOF-catalyzed reaction conditions were optimized, leading to the selection of water as the solvent, in the presence of 10% mol sodium dodecyl sulfate (SDS) to address substrate solubility. The Cu(II)-PEIP catalyst showed excellent activity under these green and mild conditions, exhibiting comparable or, in some cases, superior efficiency to a homogeneous catalyst often employed in Diels–Alder reactions, namely, Cu(OTf)₂. The nature of the azachalcone substituent played a significant role in the reactivity of the dienophiles, with electron-withdrawing (EW) substituents enhancing conversion and electron-donating (ED) ones exhibiting the opposite effect. Coordinating substituents appeared to enhance the endo selectivity. Importantly, the Cu(II)-PEIP catalyst can be readily isolated from the reaction mixture and recycled up to four times without any significant reduction in conversion or selectivity. Full article