Search Results (11)

Uric acid (UA) detection is critical for human health monitoring, necessitating the development of electrochemical sensing electrodes suitable for physiological environments. This study evaluated four 2D conductive metal–organic frameworks (2D c-MOFs), namely Cu-HHTP, Ni-HHTP, Cu-HAB, and Ni-HAB, which share identical graphene-like 2D sheet structures but differ in π-conjugation extent and catalytic active centers [MX₄] (M = Cu or Ni; X = O or NH) as electrosensing electrodes. Electrochemical sensing performance was compared by detecting UA in phosphate-buffered saline (PBS). Herein, the Ni-HHTP electrode demonstrated superior sensitivity (6.79 μA·μM⁻¹·cm⁻²), the lowest oxidation potential (0.272 V), and the lowest detection limit (0.44 μM). Langmuir adsorption isotherm analysis revealed that the Ni-HHTP electrode possesses the highest surface coverage (Γ_A) (5061.16 pmol cm⁻²) and the most favorable Gibbs adsorption free energy (ΔG°) (−18.775 kJ mol⁻¹), indicating its strongest UA adsorption capacity and molecular interaction. This enhanced performance is attributed to the optimal synergy between [NiO₄] catalytic centers and extended ligand π-conjugation, facilitating greater analyte adsorption and electron transfer efficiency. This work establishes clear structure–performance relationships for 2D c-MOF electrodes in UA detection, providing key insights for designing advanced electrosensing materials. Full article

Covalent organic frameworks (COFs) have unique features, including intrinsic porosity, crystallinity, and tunability, making them desirable materials for diverse applications ranging from environmental remediation to energy harvesting. Among these applications, COFs are extensively studied for their photocatalytic hydrogen evolution by converting solar energy into clean and renewable fuel via water splitting. COFs have several advantages over conventional inorganic catalysts, such as tunable band structures, high surface areas, and low cost. However, the research in this field is still in the early stages, and COFs still face some challenges, such as low charge carrier mobility, high exciton binding energy, and poor stability. To overcome these challenges, various design strategies relying on a mechanistic approach have been developed to design and modify COFs for enhanced photocatalytic performance. These include extending the π-conjugation, incorporating heteroatoms or metal complexes, and donor–acceptor (D–A) configuration, which ultimately improves the light absorption charge separation of COFs. Additionally, blending COFs with other functional materials, such as inorganic-organic semiconductors, can create synergistic effects to boost photocatalytic activity. In this review, the design aspects of the fabrication of COFs as effective photocatalysts have been reported. Full article

There are many efforts reported on finding effective catalysts for oxygen evolution reactions (OERs), which are important reactions in the energy field. Coordination polymers, including metal–organic frameworks (MOFs), are attracting attention as electrocatalysts for OERs due to their versatility and modulating properties. A new cobalt complex containing trans-cinnamate and 2-aminopyridmidine ligands was synthesized using a hydrothermal method. The cobalt complex showed a 1D chain structure. The electrocatalytic activity and stability of the cobalt complex with or without an electrochemical supporter, such as reduced graphene oxide (rGO), OERs were investigated and compared with a metal oxide reference material. Due to the π-conjugated trans-cinnamate, which has electron flexibility near the Co centers, the catalyst/rGO composite showed significant catalytic activities, with an overpotential of 386 mV and a Tafel slope of 64 mV/dec. Full article

Magnetic metal–organic frameworks (MMOFs) are gaining increased attention as emerging adsorbents/water remediation agents. Herein, a facile development of novel MMOFs comprised of coated ferrite nanoparticles (MNPs) and UiO-66 metal–organic framework is reported. In specific, coated Co- and Zn-doped ferrite magnetic nanoparticles were synthesized as building block while the metal–organic framework was grown in the presence of MNPs via a semi-self-assembly approach. The utilization of coated MNPs facilitated the conjugation and stands as a novel strategy for fabricating MMOFs with increased stability and an explicit structure. MMOFs were isolated with 13–25 nm crystallites sizes, 244–332 m²/g specific surface area (SSA) and 22–42 emu/g saturation magnetization values. Establishing the UiO-66 framework via the reported semi-self-assembly resulted in roughly 70% reduction in both magnetic properties and SSA, compared with the initial MNPs building blocks and UiO-66 framework, respectively. Nonetheless, the remaining 30% of the magnetization and SSA was adequate for successful and sufficient adsorption of two different pesticides, 2,4-Dichlorophenoxyacetic acid (2,4-D) and 2,4,5-Trichlorophenoxyacetic acid (2,4,5-T), while the recovery with a commercial magnet and reuse were also found to be effective. Adsorption and kinetic studies for all three MMOFs and both pesticides were performed, and data were fitted to Langmuir–Freundlich isotherm models. Full article

Pursuing novel materials with efficient photothermal conversion under irradiation at the near-infrared region windows (NIR, 750–850 nm; NIR-I and NIR-II, 1000–1320 nm)) is of great importance due to their irreplaceable applications, especially in the biomedical field. Herein, on the basis of a coordination chemistry strategy, an iron-based metal-organic framework (MOF) of [N(CH₃)₄]₂[Fe₃(NDC)₄]·DMF·3H₂O (Fe-NDC, 1,4-H₂NDC = 1,4-naphthalenedicarboxylic acid, N(CH₃)₄⁺ = tetramethyl-ammonium, and DMF = N,N-dimethylformamide) was prepared and characterized. Due to the d-d transition effect introduced by coordination with the transition-metal ion of iron and the highly conjugated naphthalenic moiety in 1,4-H₂NDC, guaranteeing an energy transfer between iron and the organic module, Fe-NDC shows a remarkable broad absorption, which could be extended into the NIR-II section. As a result, Fe-NDC could be irradiated by NIR laser (both 808 and 1064 nm) to achieve photothermal conversion. This work sets a good example to inspire the future designation of NIR light-irradiated photothermal materials based on the first-row transition metals. Full article

Amyloid aggregation is associated with many neurodegenerative diseases such as Alzheimer’s disease (AD). The current technologies using phototherapy for amyloid inhibition are usually photodynamic approaches based on evidence that reactive oxygen species can inhibit Aβ aggregation. Herein, we report a novel combinational photothermally assisted photo-oxygenation treatment based on a nano-platform of the brain-targeting peptide RVG conjugated with the 2D porphyrinic PCN−222 metal–organic framework and indocyanine green (PCN−222@ICG@RVG) with enhanced photo-inhibition in Alzheimer’s Aβ aggregation. A photothermally assisted photo-oxygenation treatment based on PCN@ICG could largely enhance the photo-inhibition effect on Aβ₄₂ aggregation and lead to much lower neurotoxicity upon near-infrared (NIR) irradiation at 808 nm compared with a single modality of photo-treatment in both cell-free and in vitro experiments. Generally, local photothermal heat increases the instability of Aβ aggregates and keeps Aβ in the status of monomers, which facilitates the photo-oxygenation process of generating oxidized Aβ monomers with low aggregation capability. In addition, combined with the brain-targeting peptide RVG, the PCN−222@ICG@RVG nanoprobe shows high permeability of the human blood–brain barrier (BBB) on a human brain-on-a-chip platform. The ex vivo study also demonstrates that NIR-activated PCN−222@ICG@RVG could efficiently dissemble Aβ plaques. Our work suggests that the combination of photothermal treatment with photo-oxygenation can synergistically enhance the inhibition of Aβ aggregation, which may boost NIR-based combinational phototherapy of AD in the future. Full article

Recently, two-dimensional metal–organic frameworks have received increasing interest due to their flexible components with adjustable structures, abundant accessible active sites, and high conductivity. In this paper, the thermal stability and electronic structure of 2D transition metal–organic framework (TM-O MOF, TM = Mn, Fe, Co, Ni) single-layer structures are systematically explored using first-principles calculations. Theoretical results reveal that these TM-O MOF systems exhibit good thermal stability due to sufficient π-electron conjugation and effective interaction between the transition metal and the organic ligands. They all show metallic behavior with spin magnetism. The catalytic property of TM-O MOFs depends on the d-electron occupations in the TM atoms. Interestingly, the active sites of HER and OER are O atoms and TM atoms, respectively, enhancing the water splitting process. The Co-O MOF shows a good HER and OER catalysis performance with the Gibbs free energy of adsorbed hydrogen atoms ΔG_*H = 0.02 eV and the over potential η^OER = 0.53 V. The insights confirm the stability and highlight the outstanding water splitting catalytic performance of 2D MOFs under normal reaction conditions. Full article

Covalent organic framework (COF) has been attracting considerable attention as a novel crystalline material owing to its extended π-electron conjugation and excellent spectral behavior. In this study, we present an imine-linked two-dimensional (2D) crystalline sulfone-based covalent organic framework (TAS-COF) synthesized by 2,4,6-triformylphloroglucinol (Tp) and 3,7-diaminodibenzo[b,d]thiophene (DAS) via a Schiff base condensation reaction. The benzothiophene sulfone endows the as-synthesized TAS-COF with excellent oxidase-like activity under visible light irradiation, ascribed to the generation of superoxide radicals (O₂^•−) by photo-generated electron transfer. TAS-COF can efficiently oxidase the colorless substrate 3,3′,5,5′-tetramethylbenzydine (TMB) into blue oxidized TMB (oxTMB) when exposed to visible light, and the presence of uranium (UO₂²⁺) leads to clear color fading due to the coordination between the imine of oxTMB and UO₂²⁺. A colorimetric strategy is thus developed for UO₂²⁺ determination with a detection limit of 0.07 μmol L⁻¹. Moreover, a paper-based visual sensing platform is also constructed to offer simple and fast UO₂²⁺ content evaluation in water samples. The present study not only provides a promising strategy to prepare visible light-triggered COF-based metal-free nanoenzymes but also extends the applications of COF material in radionuclide detection. Full article

The electronic conductive metal-organic frameworks (EC-MOFs) based on a single ligand are not suitable for the accurate detection of bisphenol A (BPA) due to the limitations of their electron-transfer-based sensing mechanism. To overcome this drawback, we developed EC-MOFs with novel dual-ligands, 2,3,6,7,10,11-hexahydroxy-sanya-phenyl (HHTP) and tetrahydroxy 1,4-quinone (THQ), and metal ions. A new class of 2D π-conjugation-based EC-MOFs (M-(HHTP)(THQ)) was synthesized by a self-assemble technique. Its best member (Cu-(HHTP)(THQ)) was selected and combined with reduced graphene (rGO) to form a Cu-(HHTP)(THQ)@rGO composite, which was thoroughly characterized by X-ray diffraction, field scanning electron microscopy, and energy-dispersive X-ray spectroscopy. Cu-(HHTP)(THQ)@rGO was drop-cast onto a glassy carbon electrode (GCE) to obtain a sensor for BPA detection. Cyclic voltammetry and electrochemical impedance tests were used to evaluate the electrode performance. The oxidation current of BPA on the Cu-(HHTP)(THQ)@rGO/GCE was substantially higher than on unmodified GCE, which could be explained by a synergy between Cu-(HHTP)(THQ) (which provided sensing and adsorption) and rGO (which provided fast electron conductivity and high surface area). Cu-(HHTP)(THQ)@rGO/GCE exhibited a linear detection range for 0.05–100 μmol·L⁻¹ of BPA with 3.6 nmol·L⁻¹ (S/N = 3) detection limit. We believe that our novel electrode and BPA sensing method extends the application perspectives of EC-MOFs in the electrocatalysis and sensing fields. Full article

A novel Zn(II) metal-organic framework [Zn₄O(C₃₀H₁₂F₄O₄S₈)₃]_n, namely ZnBPD-4F4TS, has been constructed from a fluoro- and thiophenethio-functionalized ligand 2,2′,5,5′-tetrafluoro-3,3′,6,6′-tetrakis(2-thiophenethio)-4,4′-biphenyl dicarboxylic acid (H₂BPD-4F4TS). ZnBPD-4F4TS shows a broad green emission around 520 nm in solid state luminescence, with a Commission International De L’Eclairage (CIE) coordinate at x = 0.264, y = 0.403. Since d¹⁰-configured Zn(II) is electrochemically inert, its photoluminescence is likely ascribed to ligand-based luminescence which originates from the well-conjugated system of phenyl and thiophenethio moieties. Its luminescent intensities diminish to different extents when exposed to various metal ions, indicating its potential as an optical sensor for detecting metal ion species. Furthermore, ZnBPD-4F4TS and its NH₄Br-loaded composite, NH₄Br@ZnBPD-4F4TS, were used for proton conduction measurements in different relative humidity (RH) levels and temperatures. Original ZnBPD-4F4TS shows a low proton conductivity of 9.47 × 10⁻¹⁰ S cm⁻¹ while NH₄Br@ZnBPD-4F4TS shows a more than 25,000-fold enhanced value of 2.38 × 10⁻⁵ S cm⁻¹ at 40 °C and 90% RH. Both of the proton transport processes in ZnBPD-4F4TS and NH₄Br@ZnBPD-4F4TS belong to the Grotthuss mechanism with E_a = 0.40 and 0.32 eV, respectively. Full article

Metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) are two innovative classes of porous coordination polymers. MOFs are three-dimensional materials made up of secondary building blocks comprised of metal ions/clusters and organic ligands whereas COFs are 2D or 3D highly porous organic solids made up by light elements (i.e., H, B, C, N, O). Both MOFs and COFs, being highly conjugated scaffolds, are very promising as photoactive materials for applications in photocatalysis and artificial photosynthesis because of their tunable electronic properties, high surface area, remarkable light and thermal stability, easy and relative low-cost synthesis, and structural versatility. These properties make them perfectly suitable for photovoltaic application: throughout this review, we summarize recent advances in the employment of both MOFs and COFs in emerging photovoltaics, namely dye-sensitized solar cells (DSSCs) organic photovoltaic (OPV) and perovskite solar cells (PSCs). MOFs are successfully implemented in DSSCs as photoanodic material or solid-state sensitizers and in PSCs mainly as hole or electron transporting materials. An innovative paradigm, in which the porous conductive polymer acts as standing-alone sensitized photoanode, is exploited too. Conversely, COFs are mostly implemented as photoactive material or as hole transporting material in PSCs. Full article