Photostable Ag(I)-Based Metal-Organic Framework: Synthesis, Structure, and Photocatalytic Selective Oxidation Properties

Metal–organic framework based on flexible ligands and CoII–CoII–CoII system: selective gas adsorption and magnetic properties

A novel MOF material shows unique magnetic characteristics and selective absorption properties for CO2.

Magnetically Recyclable Fe3O4@TMU-32 Metal-Organic Framework Photocatalyst for Tetracycline Degradation Under Visible Light

Metal-organic frameworks (MOFs) are a new class of porous crystalline materials being used as photocatalysts for efficient pollutant removal and environmental remediation. In this study, the TMU-32 MOF was synthesized as an effective photocatalyst for the photodegradation of tetracycline (TC) with 96% efficiency in 60 min under visible light. The high photocatalytic activity of the TMU-32 MOF is mainly due to its large specific surface area, which is beneficial for promoting both the adsorption of TC and the separation of the photoinduced charges. Moreover, its desired crystallinity makes it a semiconductor with an appropriate band gap energy. Next, a composite of the TMU-32 MOF with Fe₃O₄ nanoparticles (as Fe₃O₄@TMU-32) was prepared as a magnetically recyclable photocatalyst. The results showed that the photocatalytic activity of the Fe₃O₄@TMU-32 nanocomposite is slightly lower (68% degradation of TC within 60 min) than that of TMU-32 toward TC degradation since Fe₃O₄ nanoparticles are not acting as a photocatalyst and are used only to make the host photocatalyst (here, TMU-32) magnetically separable. The effects of the photocatalyst concentration and recyclability on the photodegradation of TC were studied under similar conditions. We found that the Fe₃O₄@TMU-32 composite is easily recycled without a significant loss of photocatalytic activity after being used several times, indicating the stability of the photocatalyst. Finally, a density functional theory study was also conducted to investigate the structural and electronic properties such as the band gap energy and density of states of the TMU-32 MOF and the Fe₃O₄@TMU-32 composite. Our computational results are in good agreement with the experimental ones. A photocatalytic degradation mechanism was finally proposed under visible-light photoirradiation.

Enhanced photocatalytic driven hydroxylation of phenylboric acid to phenol over pyrenetetrasulfonic acid intercalated ZnAl-LDHs

Layered double hydroxides (LDHs) own admirable potential due to their controllable composition and exchangeable interlayer anions. Herein, pyrenetetrasulfonic acid (PTS) intercalated ZnAl-LDHs (denoted as ZnAl-xPTS, x represents the amount of NaPTS in the starting material) are synthesized by a co-precipitation method, which display enhanced photocatalytic activity towards the hydroxylation of phenylboric acid to phenol. Various characterizations suggest that PTS plays significant roles in improving the photocatalytic activity: (1) PTS extends the light absorption from ultraviolet to visible light region; (2) the introduction of PTS upshifts the conduction band, which is feasible for the formation of O₂^∙-; (3) ZnAl-xPTS produces more free electrons under light irradiation, which leads to greatly improved activity. This study develops an alternative LDHs based photocatalyst for the production of phenol, which also provides an efficient strategy to improve the photocatalytic activity of LDHs.

Enhanced singlet oxygen production over a photocatalytic stable metal organic framework composed of porphyrin and Ag

Porphyrin is an important photosensitizer for singlet oxygen (¹O₂) formation. However, porphyrin derivatives still display low efficiency and difficult recovery. In this work, an Ag-based MOFs (AgTPyP; TPyP, 5,10,15,20-tetra(4-pyridyl) porphyrin) is synthesized. Compared with ligand TPyP, AgTPyP shows nearly 100% conversion and selectivity in the photocatalytic selective oxidation of sulfides to sulfoxides and obvious photodynamic therapeutic effect under visible light. Combined characterizations suggest that ¹O₂ is the only active oxygen species, which is due to the large exciton binding energy and narrow energy gap between the lowest excited singlet state (S₁) and the lowest triplet state (T₁) induced by the presence of Ag⁺ ion. The selectivity and conversion efficiency of five-cycle experiments do not decrease, indicating the excellent stability of AgTPyP. This work provides an alternative approach to simultaneously enhance the exciton effect of porphyrin and stabilize Ag-based photocatalysts.

Ditopic Phosphide Oxide Group: A Rigidifying Lewis Base to Switch Luminescence and Reactivity of a Disilver Complex

Heterodentate phosphines containing anionic organophosphorus groups remain virtually unexplored ligands in the coordination chemistry of coinage metals. A hybrid phosphine-phosphine oxide (o-Ph₂PC₆H₄)₂P(O)H (HP³O) readily forms the disilver complex [Ag₂(P³O)₂] (1) upon deprotonation of the (O)P-H fragment. Due to the electron-rich nature, the anionic phosphide oxide unit in 1 takes part in efficient intermolecular hydrogen bonding, which has an unusual and remarkably strong impact on the photoluminescence of 1, changing the emission from red (644 nm) to green-yellow (539 nm) in the solid. The basicity of the R₂(O)P^- group and its affinity for both inter- and intramolecular donor-acceptor interactions allow converting 1 into hydrohalogenated (2, 3) and boronated (4) derivatives, which reveal a gradual hypsochromic shift of luminescence, reaching the wavelength of 489 nm. Systematic variable-temperature analysis of the excited state properties suggests that thermally activated delayed fluorescence is involved in the emission process. The long-lived excited states for 1-4, the energy of which is largely regulated by means of the phosphide oxide unit, are potentially suitable for triplet energy transfer photocatalysis. With the highest T₁ energy among 1-4, complex 4 demonstrates excellent photocatalytic activity in a [2+2] cycloaddition reaction, which has been realized for the first time for silver(I) compounds.