In Situ Implanting ZrW2 O7 (OH)2 (H2 O)2 Nanorods into Hierarchical Functionalized Metal-Organic Framework via Solvent-Free Approach for Upgrading Catalytic Performance.

Host-guest catalyst provides new opportunities for targeted applications and the development of new strategies for preparing host-guest catalysts is highly desired. Herein, an in situ solvent-free approach is developed for implanting ZrW2 O7 (OH)2 (H2 O)2 nanorods (ZrW-NR) in nitro-functionalized UiO-66(Zr) (UiO-66(Zr)-NO2 ) with hierarchical porosity, and the encapsulation of ZrW-NR enables the as-prepared host-guest catalyst remarkably enhanced catalytic performance for both for oxidative desulfurization (ODS) and acetalization reactions. ZrW-NR@UiO-66(Zr)-NO2 can eliminate 500 ppm sulfur within 9 min at 40 °C in ODS, and can transform 5.6 mmol benzaldehyde after 3 min at room temperature in acetalization reaction. Its turnover frequencies reach 72.3 h-1 at 40 °C for ODS which is 33.4 times higher than UiO-66(Zr)-NO2 , and 28140 h-1 for acetalization which is the highest among previous reports. Density functional theory calculation result indicates that the W sites in ZrW-NR can decompose H2 O2 to WVI -peroxo intermediates that contribute to catalytic activity for the ODS reaction. This work opens a new solvent-free approach for preparing MOFs-based host-guest catalysts to upgrade their redox and acid performance.

Boosting Catalytic Performance of MOF-808(Zr) by Direct Generation of Rich Defective Zr Nodes via a Solvent-Free Approach.

Creation of rich open metal sites (defect) on the nodes of metal-organic frameworks (MOFs) is an efficient approach to enhance their catalytic performance in heterogeneous reactions; however, direct generation of such defects remains challenging. In this contribution, we developed an in situ green route for rapid fabrication of defective MOF-808(Zr) with rich Zr-OH/OH2 sites (occupying 25% Zr coordination sites) and hierarchical porosity without the assistance of formic acid and solvent. The optimal MOF-808(Zr) not only displayed superior activity in oxidative desulfurization (ODS) for removing 1000 ppm sulfur at ambient temperature within 20 min but also could convert 3.8 mmol of benzaldehyde to (dimethoxymethyl)benzene within 90 s at 30 °C. The turnover frequencies reached 45.4 h-1 for ODS and 3451 h-1 for acetalization, outperforming the most reported MOF-based catalysts. Theoretical calculation and experimental results show that the formed Zr-OH/OH2 can react with H2O2 to generate peroxo-zirconium species, which readily oxidize the sulfur compound. Our work provides a new approach to the synthesis of defect-rich MOF-808(Zr) with the accessibility of active sites for target reactions.

Defective Metal-Organic Frameworks with Tunable Porosity and Metal Active Sites for Significantly Improved Performance in Styrene Oxidation.

Metal active sites and sufficient porosity in metal-organic frameworks (MOFs) are crucial parameters determining the performances of catalysis, guest molecule adsorption, etc. Herein, through in situ introduction of Ru sites with different levels to Cu-BTC structure together with post-synthetic activation at 180 °C, a series of hierarchically porous CuRu-BTC (HP-CuRu-BTC) MOFs were obtained. Besides, selective thermal decomposition (STD) treatment was carried out at 240 °C to further tune the hierarchical pores and metal sites, yielding rare case of metal nanoparticles (NPs)@HP-CuRu-BTC composites. After full characterization by XRD, N2 physisorption, SEM, ICP and XPS, these HP-CuRu-BTC and NPs@HP-CuRu-BTC samples possess high surface area (682-1199 m2 g-1 ), hierarchical pores and highly distributed metal sites with reduced oxidation states (Cu+ and Ru2+ ), indicating regulation of both metal sites and hierarchical pores. The HP-CuRu-BTC and NPs@HP-CuRu-BTC were further employed as catalysts for the heterogeneous styrene oxidation reaction under mild condition. Compared to microporous Cu-BTC with unary metal component, HP-CuRu-BTC-3 and NPs@HP-CuRu-BTC-3 exhibited more than 2 times higher styrene conversion after 7 hours reaction under same condition.

Understanding the effects of co-exposed facets on photocatalytic activities and fuel desulfurization performance in BiOCl singlet-crystalline sheets.

Two kinds of well-crystallized BiOCl singlet-crystalline sheets (BOC-01 with twin-facet co-exposure of {001} and {110} and BOC-02 with tri-facet co-exposure of {001}, {110}, and {010}) were prepared and characterized. The photocatalytic desulfurization performance of BOC-01 and BOC-02 was tested by using n-decane and tetradecane as model oil containing heterocyclic sulfur-containing compounds (benzothiophene, or dibenzothiophene, or 4,6-dimethyldibenzothiophene). The desulfurization performance showed that twin-facet co-exposed BOC-01 had a slightly higher photocatalytic activity than tri-facet co-exposed BOC-02. The differences of photocatalytic activity between BOC-01 and BOC-02 were further explored by paramagnetic resonance spectroscopy, ultraviolet diffuse reflectance spectroscopy, steady-state and time-resolved prompt fluorescencespectra. The results disclosed that the exciton effect in BOC-01 played a key role in photocatalytic activation of molecular oxygen, while BOC-02 mainly produced reactive oxygen species by charge transfer. Theoretical calculations further indicated that the photogenerated electrons are mainly distributed on the {110} facets and the photogenerated holes are mainly distributed on the {001} facets in BOC-01 and BOC-02. This work provides a useful clue for an in-depth understanding of the effects of co-exposed facets in BiOCl on photocatalytic performance.

Ammonia Electrosynthesis with High Selectivity under Ambient Conditions via a Li+ Incorporation Strategy.

We report the discovery of a dramatically enhanced N2 electroreduction reaction (NRR) selectivity under ambient conditions via the Li+ incorporation into poly(N-ethyl-benzene-1,2,4,5-tetracarboxylic diimide) (PEBCD) as a catalyst. The detailed electrochemical evaluation and density functional theory calculations showed that Li+ association with the O atoms in the PEBCD matrix can retard the HER process and can facilitate the adsorption of N2 to afford a high potential scope for the NRR process to proceed in the "[O-Li+]·N2-Hx" alternating hydrogenation mode. This atomic-scale incorporation strategy provides new insight into the rational design of NRR catalysts with higher selectivity.

A comparative DFT study on aquation and nucleobase binding of ruthenium (II) and osmium (II) arene complexes.

The potential energy surfaces of the reactions of organometallic arene complexes of the type [(η (6)-arene)M(II)(pic)Cl] (where pic = 2-picolinic acid, M = Ru or Os) were examined by a DFT computational study. Among the seven density functional methods, hybrid exchange functional B3LYP outperforms the others to explain the aquation of the complexes. The reactions and binding energies of Ru(II) and Os(II) arene complexes with both 9EtG and 9EtA were studied to gain insight into the reactivity of these types of organometallic complexes with DNA. The obtained data rationalize experimental observation, contributing to partly understanding the potential biological and medical applications of organometallic complexes.

DFT study of a series of crown-4 ethers and their selectivity trend for alkali metal cations: Li+ and Na+.

The molecular and electronic structures for 12- to 16-crown-4 (named 12C4, 13C4, 14C4, 15C4, 16C4, respectively) and 2,3,5,6,8,9-hexahydrobenzo[b][1,4,7,10] tetraoxacyclododecine (B12C4) 3,5,6,7,9,10-hexahydro-2H-benzo[e][1,4,7,10]tetraoxacyclotridecine (B13C4) and their complexes with alkali metal cations Li+ and Na+ have been explored using the density functional theory (DFT) with B3LYP/ 6-31G* method. The nucleophilicity of crown-4 ethers has been investigated by the Fukui function. Their selectivity trend shows that of all the crown-4 ethers, 14C4 shows the highest cation selectivity for Li+ over Na+, has been achieved on the basis of thermodynamic analysis. In addition, Li+/crown-4 series are more stable than Na+/crown-4 series in the gas phase. The calculated results are in good agreement with the experimental observation.