Facet-Dependent Photocatalytic Behavior of Fe-soc-MOF for Carbon Dioxide Reduction.

Exposing different facets on metal-organic frameworks (MOFs) is an efficient approach to regulate their photocatalytic performance for CO2 reduction. Herein, Fe-soc-MOFs exposed with different facets were successfully synthesized, and the morphologies of Fe-soc-MOF exposed with eight {111} facets (Fe-soc-O) and that exposed with eight {111} and six {100} crystal facets (Fe-soc-M) are first reported. Fe-soc-MOFs have facet-dependent active sites on their surface and correspondingly different catalytic performance for photocatalytic CO2 reduction. Fe-soc-O has the highest CO production of 1804 µmol g-1 h-1, while the Fe-soc-MOF exposed with six {100} facets (Fe-soc-C) has the best CO selectivity of 94.7%. Density functional theory (DFT) calculations demonstrate that the (111) facet has more favorable thermodynamic potential for CO2 reduction and H2 evolution compared with the (100) one, deriving from its facet-dependent active sites. This work shows that utilizing the facet-engineering strategy to regulate the active sites exposed on the surface of MOFs is feasible. The results display the relation between the facet of MOFs and the photocatalytic behavior for CO2 reduction.

Ti(IV)-MOF with Specific Facet-Ag Nanoparticle Composites for Enhancing the Photocatalytic Activity and Selectivity of CO2 Reduction.

Metal nanoparticles deposited in the photocatalyst not only can serve as a cocatalyst but also can act as a light harvester to extend the light absorption, resulting from the surface plasmon resonance (SPR). In this study, we deposited silver nanoparticles (Ag NPs) onto NH2-MIL-125(Ti) with exposed specific facets and achieved effectively improved activity and selectivity for photocatalytic CO2 reduction. Loading Ag NPs on the exposed {111} facets of NH2-MIL-125(Ti) generates a highly effective composite catalyst for the photoreduction of CO2, resulting in the maximal CO and CH4 yields of 26.7 and 63.3 µmol g-1 h-1, respectively, which are 2.2- and 16.2-fold those of the NH2-MIL-125(Ti) exposing {111} facets, and a CH4 selectivity of 90.5%. Incorporation of Ag NPs not only optimizes the electronic structure of the photocatalyst but also suppresses the recombination of photogenerated electron-hole pairs. This study provides an exciting example for creating and understanding metal-decorated facet-dependent effects on metal-organic frameworks (MOFs) for photocatalytic reactions.

Coordination Polymers with 2,2':6',2″-Terpyridine Earth-Abundant Metal Complex Units for Selective CO2 Photoreduction.

Combining molecular metal complexes into coordination polymers (CPs) is an effective strategy for developing photocatalysts for CO2 reduction; however, most such reported catalysts are noble metal-containing CPs. Herein, two novel Zr-containing bimetallic CPs, Co-Zr and Ni-Zr, were designed and successfully synthesized by connecting 2,2':6',2″-terpyridine-based molecular earth-abundant metal (Co or Ni) complexes with ZrO8 nodes. Both CPs were applied as catalysts for CO2 photoreduction to selectively produce CO. The catalytic performance of Co-Zr is better than that of Ni-Zr with a yield of 3654 µmol (g of catalyst)-1 for CO in 6 h (TON = 18.2). The difference between these two catalysts was analyzed with respect to band structure and charge migration ability. This work provides an effective way to introduce molecular earth-abundant metal complexes into coordination polymers for the construction of efficient noble metal-free CO2 photocatalysts.

Effect of the Defect Modulator and Ligand Length of Metal-Organic Frameworks on Carbon Dioxide Photoreduction.

The nature of defects and organic ligands can fine-tune the absorption energy (Eabs) of metal-organic frameworks (MOFs), which is crucial for photocatalytic reactions; however, the relevant studies are in their infancy. Herein, a series of typical MOFs of the UiO family (UiO-6x-NH2, x = 8, 7, and 6) with ligands of varied lengths and amino-group-modified defects were synthesized and employed to explore their performance for photocatalytic CO2 reduction. Sample UiO-66-NH2-2ABA (2ABA = 3,5-diamino-benzoate) with the shortest dicarboxylate ligand and two amino-group-modified defects exhibits superior photocatalytic activity due to the lowest Eabs. The CO yield photocatalyzed by UiO-66-NH2-2ABA is 17.5 µmol g-1 h-1, which is 2.4 times that of UiO-68-NH2-BA (BA = benzoate) with the longest ligand and no amino group involved in the defects. Both the experiments and theoretical calculations show that shorter dicarboxylate ligands and more amino groups result in smaller Eabs, which is favorable for photocatalytic reactions. This study provides new insights into boosting the photocatalytic efficiency by modulating the defects and ligands in MOFs.

PPAR-γ Ligand Inhibits Nasopharyngeal Carcinoma Cell Proliferation and Metastasis by Regulating E2F2.

PURPOSE: Peroxisome proliferator-activated receptor-γ (PPAR-γ) is a nuclear hormone receptor with a key role in lipid metabolism. Previous studies have identified various roles of PPAR-γ in cell cycle progression, cellular proliferation, and tumor progression. However, no report has described a role for PPAR-γ in human nasopharyngeal carcinoma (NPC). Notably, some studies have reported a relationship between PPAR-γ and E2F transcription factor 2 (E2F2), which has been identified as a regulator of cell cycle, apoptosis, and the DNA damage response. Notably, E2F2 has also been reported to correlate with a poor prognosis in patients with various malignancies. METHODS: We used immunohistochemical (IHC) and western blot methods to evaluate PPAR-γ and E2F2 expression and function in nonkeratinizing NPC and nasopharyngitis (NPG) tissue samples, as well as western blotting and CCK8 analyses in the NPC cell lines, CNE1 and CNE2. RESULTS: We observed lower levels of PPAR-γ expression in nonkeratinizing NPC tissues compared with NPG tissues and determined an association between a low level of PPAR-γ expression with a more advanced tumor stage. Furthermore, strong E2F2 expression was detected in nonkeratinizing NPC tissues. We further demonstrated that rosiglitazone, a PPAR-γ agonist, reduced E2F2 expression and proliferation in NPC cell lines. CONCLUSIONS: Our study results revealed a novel role for the PPAR-γ-E2F2 pathway in controlling NPC cell proliferation and metastasis.