RESUMEN
The conversion of CO2 to C2 through photocatalysis poses significant challenges, and one of the biggest hurdles stems from the sluggishness of the multi-electron transfer process. Herein, taking metal-organic framework (PFC-98) as a model photocatalyst, we report a new strategy to facilitate charge separation. This strategy involves matching the energy levels of the lowest unoccupied node and linker orbitals of the MOF, thereby creating the lowest unoccupied crystal orbital (LUCO) delocalized over both the node and linker. This feature enables the direct excitation of electrons from photosensitive linker to the catalytic centers, achieving a direct charge transfer (DCT) pathway. For comparison, an isoreticular MOF (PFC-6) based on analogue components but with far apart frontier energy level was synthesized. The delocalized LUCO caused the presence of an internal charge-separated state (ICS), prolonging the excited state lifetime and further inhibiting the electron-hole recombination. The presence of an internal charge-separated state (ICS) prolongs the excited state lifetime and further inhibits the electron-hole recombination. Moreover, it also induced abundant electrons accumulating at the catalytic sites, enabling the multi-electron transfer process. As a result, the material featuring delocalized LUCO exhibits superior overall CO2 photocatalytic performance with high C2 production yield and selectivity.
RESUMEN
While the construction of a donor-acceptor (D-A) structure has gained great attention across various scientific disciplines, such structures are seldomly reported within the field of hydrogen-bonded organic frameworks (HOFs). Herein, a D-A based HOF is synthesized, where the adjacent D-A pairs are connected by hydrogen bonds instead of the conventionally employed covalent bonds. This structural feature imparts material with a reduced energy gap between excited state and triplet state, thereby facilitating the intersystem crossing (ISC) and boosting the generation rate of single oxygen (quantum yield = 0.98). Consequently, the resulting material shows high performance for antimicrobial photodynamic therapy (PDT). The impact of D-A moiety is evident when comparing this finding to a parallel study conducted on an isoreticular HOF without a D-A structure. The study presented here provides in-depth insights into the photophysical properties of D-A pair in a hydrogen-bonded network, opening a new avenue to the design of innovative materials for efficient PDT.
RESUMEN
MOF-808, owing to the synergistic effect of its large surface area and surface charge matching, showed a diclofenac sodium (DCF) removal capacity as high as 630 mg g-1, and the ability to adsorb 436 mg g-1 DCF in two hours, outperforming many common Zr-MOFs under the same conditions. Importantly, a series of free-standing mixed-matrix membranes made by combining polyacrylonitrile with MOF-808 were fabricated and exhibited high efficiency of removing DCF from water via an easily accessible filtration method.
RESUMEN
The aim of this study was to determine the effects of antioxidants, including alpha-ketoacids (alpha-ketoglutarate and pyruvate), lactate and glutamate/malate combination, against oxidative stress on rat spermatozoa. Our results showed that H(2)O(2) (250 micromol L(-1))-induced damages, such as impaired motility, adenosine triphosphate (ATP) depletion, inhibition of sperm protein phosphorylation, reduced acrosome reaction and decreased viability, could be significantly prevented by incubation of the spermatozoa with alpha-ketoglutarate (4 mmol L(-1)) or pyruvate (4 mmol L(-1)). Without exogenous H(2)O(2) in the medium, the addition of pyruvate (4 mmol L(-1)) significantly increased the superoxide anion (O(2)(-).) level in sperm suspension (P < or = 0.01), whereas the addition of alpha-ketoglutarate (4 mmol L(-1)) and lactate (4 mmol L(-1)) significantly enhanced tyrosine-phosphorylated proteins with the size of 95 kDa (P < or = 0.04). At the same time, alpha-ketoglutarate, pyruvate, lactate, glutamate and malate supplemented in media can be used as important energy sources and supply ATP for sperm motility. In conclusion, the present results show that alpha-ketoacids could be effective antioxidants for protecting rat spermatozoa from H(2)O(2) attack and could be effective components to improve the antioxidant capacity of Biggers, Whitten and Whittingham media.