Tetraphenylpyrazine-Based Manganese Metal-Organic Framework as a Multifunctional Sensor for Cu2+, Cr3+, MnO4-, and 2,4,6-Trinitrophenol and the Construction of a Molecular Logical Gate

A tetraimidazole-decorating tetraphenylpyrazine has been designed and utilized for the fabrication of a novel metal-organic framework (MOF), denoted as {Mn(Tipp)(A)₂}_n·2H₂O (TippMn, where Tipp = 2,3,5,6-tetrakis[4-[(1H-imidazol-1-yl)methyl]phenyl]pyrazine and A = deprotonation of 1,4-naphthalenedicarboxylic acid), through hydrothermal synthesis. Structural analysis reveals that TippMn possesses a 2-fold-interpenetrated 4,8-connected three-dimensional (3D) network with an unprecedented {4¹⁶·6¹²}{4⁴·6²} topology. Fluorescent spectral investigations indicate that TippMn shows discriminative fluorescence when treated by Cr³⁺ and Cu²⁺, giving an INHIBIT logical gate performance. Meanwhile, TippMn can be further used as a sensor for MnO₄^- and 2,4,6-trinitrophenol (TNP) by fluorescence quenching. Notably, the sensing processes toward Cu²⁺, Cr³⁺, MnO₄^-, and TNP are labeled with high selectivity and sensitivity, quick response, and good recyclability. It is anticipated that this MOF-based versatile sensor could shed light on the exploration of MOFs for fluorescent sensors, optical switches, etc.

Metal-organic framework (MOF) composite materials for photocatalytic CO2 reduction under visible light

The tridentate ligand 2,4,6-tris(2-(pyridin-4-yl)vinyl)-1,3,5-triazine (TPVT) was designed and synthesized. We prepared metal-organic framework (TPVT-MOFs) crystals containing TPVT, 1,3,5-benzenetricarboxylic acid and cobalt by solvothermal reaction. Then, a series of composite materials with different contents of TPVT-MOFs were obtained by combining TPVT-MOFs with g-C3N4. Due to the interaction between TPVT-MOFs and g-C3N4, the composite materials have a more favorable valence band (VB) and conduction band (CB) for photocatalytic reduction of CO2 and oxidation of H2O. Under the conditions of visible light and a gas-solid system without a co-catalyst, a photosensitizer and a sacrificial agent, the yield of CO2 reduction by TPVT-MOFs@g-C3N4-10 can reach 56.4 μmol·g-1·h-1, which is 3.2 times that of pure g-C3N4 (17.5 μmol·g-1·h-1). The results of DFT calculations showed that the adsorption of H2O on the TPVT-MOFs@g-C3N4 composite material was more preferential, which promoted the adsorption and reduction of CO2.

Robust charge carrier by Fe3O4 in Fe3O4/WO3 core-shell photocatalyst loaded on UiO-66(Ti) for urea photo-oxidation

In this study, a facile four-step hydrothermal method was utilized to deposit a core-shell structure on UiO-66(Zr/Ti) nanoflake (NFs) as a visible-light-driven photocatalyst. The core was magnetic Fe₃O₄ which served as a charge carrier coated with WO₃ shell. The as-prepared photocatalyst was characterized by XRD, VSM, BET, FTIR, FE-SEM, UV-Vis-DRS, and PL techniques which proved successful deposition of Fe₃O₄@WO₃ core/shell particle on UiO-66(Zr/Ti)-NFs. The obtained photocatalyst was subsequently applied for urea photo-oxidation. This magnetically recoverable photocatalyst exhibited superior activity due to its desirable band alignment, high stability, and generation of the photo-induced charge carriers, as well as providing a high surface area with low mass transfer resistance. Fe₃O₄ core acted as charge-carrier to transport the photogenerated charges of UiO-66(Zr/Ti)-NFs (electron-donor) to WO₃ charge-collectors for effective photoconversion. The central composite design was applied to design the experiments matrix in which flow rate, pH, irradiation time, catalyst mass, and initial urea concentration were considered as operational factors. The optimized condition was found by defining the desirability function. 90% degradation percentage was achieved at 550 mL/min solution flowrate, pH = 7, 120 min irradiation time, 0.22 g UiO-66(Zr)-NFs-Fe₃O₄@WO_3, and 40 mg/L of the initial concentration of urea with the desirability value of 0.89. Such a superior photocatalytic activity of UiO-66-Fe₃O₄@WO₃ can be ascribed to the reclamation of Fe₃O₄ as a low bandgap carrier, which accelerated the conveyance of electrons and followed surpassing charge separation. Our present findings open a new strategy to produce a wide range of core-shell heterogeneous catalysts to be applied in photoreactors scale-up.

Encapsulated anion-dominated photocatalytic and adsorption performances for organic dye degradation and oxoanion pollutant capture over cationic Cu(i)-organic framework semiconductors

Decontamination of industrial wastewater containing toxic organic dye molecules and oxoanions is urgently desirable for environmental sustainability and human health. Water-stable porous metal-organic frameworks (MOFs) have emerged as highly efficient photocatalysts and/or adsorbents for water purification through controllable integration of the constitutive requirements. To reveal the inclusion anion effect of microporous MOFs on wastewater treatment, two isostructural MOFs incorporating positive charge and semiconductive characteristics, {[Cu(tpt)]·3H₂O·0.5SO₄}_n (1) and {[Cu(tpt)]·2H₂O·ClO₄}_n (2, tpt = 2,4,6-tris(4-pyridyl)-1,3,5-triazine), have been synthesized and employed as dual-functional materials for both dye photodegradation and oxoanion removal. The two MOFs possess the same 3-fold interpenetrating cationic backbones but are encapsulated by highly disordered sulfate or perchlorate in the open channels. These included anions have significantly tuned the hydrophilicity of the channels, extended the visible-light absorption, optimized the bandgap and decreased the conduction band potential. Under the low-energy irradiation of a 30 W LED lamp, MOF 1 has selectively and efficiently degraded rhodamine B compared to 2 with accelerated kinetics, resulting from the stronger reduction ability and less migration resistance of the photogenerated electrons. Instead, MOF 2 can quickly capture harmful MnO₄^- and Cr₂O₇^2- by exchanging with the entrapped ClO₄^-, with maximum adsorption amounts of 557 and 168 mg g^-1, respectively, under ambient conditions. The improved decolorization of the aqueous solution over 2 benefits essentially from the shape and charge memory effect and the smaller hydration energy of ClO₄^- than SO₄^2-. These interesting observations highlight the importance of the included anions inside the porous MOF semiconductors on wastewater treatment.

1,3-Bis(4′-carboxylatophenoxy)benzene and 3,5-bis(1-imidazoly)pyridine derived Zn(ii)/Cd(ii) coordination polymers: synthesis, structure and photocatalytic properties

Zn(ii) and Cd(ii)-based CPs derived from a 1,3-bis(4′-carboxylatophenoxy)benzene and 3,5-bis(1-imidazoly)pyridine synthesized and their photocatalytic properties for decomposition of methylene blue investigated.

A Mixed-ligand Pb(II)-coordination Polymer: Photocatalytic Performance and Reduction Activity of the Inflammatory Response After Severe Burns by Inhibiting NF-κB Signaling Pathway

Via the employment of a mixed-ligand method, a novel Pb(II)-coordination polymer with the chemical formula of [Pb(pdc)(bdc)]·2DMF (1, H2bdc = 1,4-benzenedicarboxylic acid and H2pdc = 3,5-pyridinedicarboxylic acid) has been produced via reaction of Pb(NO3)2 with the two organic linkers in a mixed solvent of DMF and water. Complex 1 has high photocatalytic degradation efficiency for methylene blue and rhodamine B under ultraviolet light irradiation. The mechanism of photocatalysis was hypothesized and verified in detail by the r photocatalysis reaction in the existence of the hydroxyl radical scavenger mannitol. Furthermore, the influence of the inflammatory response in the severe burns rats was evaluated. Firstly, the inflammatory response levels were assessed by measuring the content of IL-6 and TNF-α in the plasma after treated with compound. Next, the real time RT-PCR was carried out to determine the signaling pathway of NF-κB relative expression in inflammatory cells.

Degradation of azo dyes under visible light with stable MOF based on tetrastyrene imidazole ligand

In the present work, a new 3D metal-organic framework (MOF) has been synthesized and characterized. The MOF exhibits good chemical stability in aqueous solutions with the pH scale ranging from 3 to 11. Interestingly, the MOF shows high catalytic activities for the degradation of azo dyes (MO, CR and CBR) under visible light without H2O2. The Ea values of the MOF for MO, CR and CBR degradation are obtained to be 23.49, 52.68 and 15.19 kJ mol-1, respectively. In addition, the MOF can be reused in the catalytic process without the catalytic activity decreasing obviously.

Cu(ii)/Ni(ii)–organic frameworks constructed from the homometallic clusters by 5-(2-carboxyphenoxy)isophthalic acid and N-ligand: synthesis, structures and visible light-driven photocatalytic properties

Four new complexes, namely, Cu₂(O-cpia)(btb)_0.5·(OH) (1), Cu₃(O-cpia)₂(bpy)₂ (2), [Ni₂(O-cpia)(phen)·(OH)·H₂O]·2H₂O (3) and [Ni₃(O-cpia)₂(bpy)₃·2H₂O]·2H₂O (4) (O-cpia = 5-(2-carboxyphenoxy)isophthalic acid, btb = 1,4-bis(1,2,4-triazol-1-yl)butane, bpy = 4,4′-bipyridine) were successfully isolated under hydrothermal conditions. The four complexes exhibit different architectures constructed from different homometallic clusters varying from mononuclear, binuclear to tetranuclear metal(ii) polyhedra as Second Building Blocks (SBUs). 1 features a 3D framework constructed from the tetranuclear clusters [Cu₄(μ₃-OH)₂] as SBUs, linked with Cu(1)O₄N and Cu(2)O₅ polyhedra by O-cpia/btb mixed linkers. 2 also exhibits a 3D structure based on trinuclear clusters [Cu₃(COO)₄] SBUs, bridged with Cu(1)O₃N₂ and Cu(2)O₄ polyhedra via O-cpia/bpy mixed ligands. 3 shows a 2D network consisting of tetranuclear clusters [Ni₄(μ₃-OH)₂] SBUs, which are bridged with Ni(1)O₄N₂ and Ni(2)O₆ through O-cpia ligands. It is worth noting that 4, with a 3D structure, is generated from the binuclear clusters [Ni₂(COO)₄] (Ni(1)O₄N) and mononuclear metal Ni(2) cores (Ni(2)O₄N₂) as SBUs, and bridged by O-cpia/bpy mixed ligands. Meanwhile, the degradation of dyes (RhB) by the complexes under visible light irradiation was studied. 1–4 are semiconducting in nature, with E_g of 1.30 eV (1), 1.78 eV (2), 2.85 eV (3) and 2.14 eV (4). Cu(ii) complexes 1 and 2 are highly efficient photocatalysts for the degradation of RhB under visible light irradiation.

Four Cu(ii)/Ni(ii)-metal–organic frameworks were constructed from different homometallic clusters by O-cpia/N-ligands. Cu(ii)-complexes show highly efficient photocatalysts for the degradation of RhB under visible light irradiation.

A new triazine-based covalent organic polymer for efficient photodegradation of both acidic and basic dyes under visible light

COP-NT can be used as an efficient photocatalyst for the degradation of methyl orange (MO), rhodamine B (RhB) and methylene blue (MB).

A new V-doped Bi2(O,S)3 oxysulfide catalyst for highly efficient catalytic reduction of 2-nitroaniline and organic dyes

A new type of convenient, and environmentally friendly, Vanadium (V)-doped Bi₂(O,S)₃ oxysulfide catalyst with different V contents was successfully synthesized via a simple and facile method. The obtained V-doped Bi₂(O,S)₃ solid solution catalysts were fully characterized by conventional methods. The catalytic performance of the samples was tested by using the reduction of 2-nitroaniline (2-NA) in aqueous solution. The reduction/decolorization of methylene blue (MB) and rhodamine B (RhB) was also chosen to evaluate the universality of catalysts. It was observed that the introduction of V can improve the catalytic performance, and 20%V-Bi₂(O,S)₃ was found to be the optimal V doping concentration for the reduction of 2-NA, MB, and RhB dyes. For comparative purposes, a related V-free Bi₂(O, S)₃ oxysulfide material was synthesized and tested as the catalyst. The superior activity of V-doped Bi₂(O,S)₃ over pure Bi₂(O,S)₃ was ascribed mainly to an increase in active sites of the material and also due to the presence of synergistic effects. The presence of V⁵⁺ as found from XPS analysis may interact with Bi atoms and enhancing the catalytic activity of the sample. In the catalytic reduction of 2-NA, MB and RhB, the obtained V-doped Bi₂(O,S)₃ oxysulfide catalyst exhibited excellent catalytic activity as compared with other reported catalysts. Furthermore this highly efficient, low-cost and easily reusable V-doped Bi₂(O,S)₃ catalyst is anticipated to be of great potential in catalysis in the future.

A series of five-coordinated copper coordination polymers for efficient degradation of organic dyes under visible light irradiation

Five-coordinated copper(ii) coordination polymers 1–5 are highly efficient and universal photocatalysts for the degradation of the organic dyes methylene blue (MB), rhodamine B (RhB) and methyl orange (MO) under visible light irradiation.