Frustrated Lewis pair boosting photocatalytic antibacterial activity on PDI-bridged bimetallic UiO-66-NH2.

Designing frustrated Lewis pair (FLP)-structured photocatalysts is a new challenge in catalysis. In particular, the relationship between the active sites and photocatalytic charge transport mechanism over FLP-structured photocatalysts is still ill-defined. In this study, a novel perylene-3,4,9,10-tetracarboxylic diimide/UiO-66(Ti/Zr)-NH2 (denoted as PDI/TUZr) photocatalyst is successfully constructed using an ammoniation process. The PDI/TUZr heterojunction is equipped with a unique "Zr/Ti SBUs-ligand-PDI" FLP structure and exhibits remarkable catalytic FLP properties. In this "Zr/Ti SBUs-ligand-PDI" structure, the Zr/Ti bimetal centers and PDI serve as Lewis acid and base sites, respectively, and the C-N chemical bond provides a channel for electron transmission, and a bimetallic system facilitates electron transfer from excited ligand to Zr/Ti-SBUs nodes. These superior microstructural designs cooperate to promote substrate activation for photocatalytic antibacterial reactions. Accordingly, 2.2-fold enhancement is achieved in visible photocatalytic antibacterial activity on Staphylococcus aureus for 4%PDI/0.2TUZr composite compared with unadorned UZr. This study provides insights into the formation and carrier transfer behaviors of solid FLP on MOFs and illustrates a rational strategy for the construction of highly efficient photocatalysts.

Amino-functionalized MIL-125(Ti) for photodenitrification of pyridine in fuels via coordination activation by unsaturated Ti4+ centers.

Due to their explicit structure, metal-organic frameworks (MOFs) have been supposed to be credible platforms to research the micro-mechanism of heterogeneous photocatalysis. In this study, amino-functionalized MOFs (MIL-125(Ti)-NH2 (denoted as MTi), UiO-66(Zr)-NH2 (denoted as UZr) and MIL-68(In)-NH2 (denoted as MIn)) with three different metal centers were synthesized and applied for the denitrification of simulated fuels under visible light irradiation, during which pyridine was used as a typical nitrogen-containing compound. The results showed that MTi had the best activity among the above three MOFs, and the denitrogenation rate increased to 80% after 4 h of visible light irradiation. On the grounds of the theoretical calculation of pyridine adsorption and actual activity experiments, it can be presumed that the unsaturated Ti4+ metal centers should be the key active sites. Meanwhile, the XPS and in situ infrared results verified that the coordinatively unsaturated Ti4+ sites facilitate the activation of pyridine molecules through the surface -N⋯Ti- coordination species. The coordination-photocatalysis synergism promotes the efficiency of photocatalytic performance and the corresponding mechanism is proposed.

Assembling Ultrafine SnO2 Nanoparticles on MIL-101(Cr) Octahedrons for Efficient Fuel Photocatalytic Denitrification.

Effectively reducing the concentration of nitrogen-containing compounds (NCCs) remains a significant but challenging task in environmental restoration. In this work, a novel step-scheme (S-scheme) SnO2@MCr heterojunction was successfully fabricated via a facile hydrothermal method. At this heterojunction, MIL-101(Cr) octahedrons are decorated with highly dispersed SnO2 quantum dots (QDs, approximate size 3 nm). The QDs are evenly wrapped around the MIL-101(Cr), forming an intriguing zero-dimensional/three-dimensional (0D/3D) S-scheme heterostructure. Under simulated sunlight irradiation (280 nm < λ < 980 nm), SnO2@MCr demonstrated superior photoactivity toward the denitrification of pyridine, a typical NCC. The adsorption capacity and adsorption site of SnO2@MCr were also investigated. Tests using 20%SnO2@MCr exhibited much higher activity than that of pure SnO2 and MIL-101(Cr); the reduction ratio of Cr(VI) is rapidly increased to 95% after sunlight irradiation for 4 h. The improvement in the photocatalytic activity is attributed to (i) the high dispersion of SnO2 QDs, (ii) the binding of the rich adsorption sites with pyridine molecules, and (iii) the formation of the S-scheme heterojunction between SnO2 and MIL-101(Cr). Finally, the photocatalytic mechanism of pyridine was elucidated, and the possible intermediate products and degradation pathways were discussed.

MOF-Derived Porous Fe2O3 Nanoparticles Coupled with CdS Quantum Dots for Degradation of Bisphenol A under Visible Light Irradiation.

In this work, CdS quantum dots (QDs) were planted on magnetically recyclable porous Fe2O3 (denoted as F450) to obtain CdS QDs/porous Fe2O3 hybrids (denoted as X-CdS/F450, in which X is the immersion times of CdS QDs). Porous Fe2O3 was first obtained by pyrolysis from an iron-containing metal-organic framework by a two-step calcination method. Next, CdS QDs (of average size 3.0 nm) were uniformly and closely attached to the porous F450 via a sequential chemical-bath deposition strategy. As expected, the X-CdS/F450 hybrids serve as high-performance photocatalysts for the degradation of bisphenol A, a typical endocrine-disrupting chemical. Almost ∼100% of the bisphenol A was degraded over 5-CdS/F450 after visible light irradiation for 30 min (λ ≥ 420 nm). In comparison, the degradation efficiency of pure F450 powder is 59.2%. The high performance of 5-CdS/F450 may be ascribable to the fast electron transport of porous F450, the intense visible-light absorption of the CdS QDs and the matched energy levels between CdS and F450. More significantly, through the photocatalytic degradation reaction, the X-CdS/F450 hybrids can easily be recovered magnetically and reused in subsequent cycles, indicating their stability and recyclability.