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119 results on '"Lin, Zu-Jin"'

48. Zr-Based Metal-Organic Frameworks with Intrinsic Peroxidase-Like Activity for Ultradeep Oxidative Desulfurization: Mechanism of H 2 O 2 Decomposition.

Author

Zheng HQ, Zeng YN, Chen J, Lin RG, Zhuang WE, Cao R, and Lin ZJ

Subjects
Catalysis, Electron Spin Resonance Spectroscopy, Hot Temperature, Kinetics, Microscopy, Electron, Scanning, Molecular Structure, Oxidation-Reduction, Powder Diffraction, Thiophenes chemistry, Metal-Organic Frameworks chemistry, Peroxidases chemistry, Sulfur chemistry, Zirconium chemistry
Abstract

The restriction of sulfur content in fuels has become increasingly stringent as a result of the growing environmental concerns. Although several MOF-derived materials like POM@MOF composites have shown the ability to catalyze oxidative desulfurization (ODS), their catalytic activities inevitably obstructed by the encapsulated catalytic sites like POM due to the blockage of cavities. Therefore, MOFs with intrinsic and accessible catalytic sites are highly desirable for their applications in ultradeep ODS. Herein, four representative Zr-based MOFs (Zr-MOFs), namely, UiO-66, UiO-67, NU-1000, and MOF-808, were assessed for catalytic ODS. These MOFs were confirmed that they have peroxidase-like activity and can catalyze ODS with H 2 O 2 as oxidant. Among them, MOF-808 showed the highest catalytic activity and it can fully desulfurize dibenzothiophene (DBT) in a model gasoline with a S concentration of 1000 ppm under 40 °C within 5 min. An extremely low apparent Arrhenius activation energy (22.0 KJ·mol -1 ) and an extraordinarily high TOF value (42.7 h -1 ) were obtained, ranking MOF-808 among the best catalysts for the catalytic DBT oxidation. Further studies confirmed that the excellent catalytic activity is mainly responsible for the high concentration of the accessible Zr-OH(H 2 O) catalytic sites decorated in MOF-808. The superoxide radicals ( • O 2 - ) and hydroxyl radicals ( • OH) were identified and were proved to involve in the DBT oxidation. Besides, the effects of Brönsted and lewis acidity to the catalytic efficiency were also discussed. Based on the experimental results, a plausible mechanism concerning on Zr-OH(H 2 O) groups promoting the H 2 O 2 decomposion in to both • O 2 - and • OH was first proposed. Moreover, MOF-808 can be facilely reused for at least eight runs without significant loss of its catalytic activity. By the integration of facile synthesis, high catalytic efficiency, and good stability, MOF-808 thus represents a new benchmark catalyst for catalytic oxidative desulfurization.

Published
2019
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49. Efficient Capture and Effective Sensing of Cr 2 O 7 2- from Water Using a Zirconium Metal-Organic Framework.

Author

Lin ZJ, Zheng HQ, Zheng HY, Lin LP, Xin Q, and Cao R

Abstract

Highly efficient decontamination of heavily toxic Cr 2 O 7 2- from water remains a serious task for public health and ecosystem protection. An easily regenerative and reused sorbent with suitable porosity may address this task. Herein, a series of water-stable and ecofriendly metal-organic frameworks (MOFs) with large surface areas were assessed for their ability to adsorb and separate Cr 2 O 7 2- from aqueous solutions. Among these tested MOFs, NU-1000 shows an extraordinary capability to efficiently capture (within 3 min) Cr 2 O 7 2- with a sorption capacity of up to 76.8 mg/g, which is the largest one for the neutral MOF-based Cr 2 O 7 2- sorbents. NU-1000 also shows remarkable selectivity for Cr 2 O 7 2- capture and can effectively reduce the Cr(VI) concentration from 24 ppm to 60 ppb, which is below the acceptable limit for the drinking water standard (100 ppb by the U.S. Environmental Protection Agency). Moreover, this adsorbent can be easily regenerated by Soxhlet extraction with an acidic methanol solution (2.5 M HCl) and can be reused at least three times without a significant loss of it adsorption ability. More intriguingly, NU-1000 can also serve as an efficient photoluminescent probe for the selective detection of Cr 2 O 7 2- in aqueous media. The Cr 2 O 7 2- detection limit is as low as 1.8 μM, and the linear range is from 1.8 to 340 μM. Our work shows that NU-1000 is a unique material combining both efficient sorption and exceptional fluorescent sensing of Cr 2 O 7 2- in aqueous media.

Published
2017
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50. A guest-dependent approach to retain permanent pores in flexible metal-organic frameworks by cation exchange.

Author

Lin ZJ, Liu TF, Huang YB, Lü J, and Cao R

Abstract

Two anionic metal-organic frameworks were successfully prepared based on pre-designed flexible multicarboxylate ligands and indium cations. Owing to the flexibility of the bridging organic linkers, which could not themselves sustain the frameworks, both of the frameworks showed thermal instability and shrinkage after removal of guest solvent molecules. Inspired by bamboo, we used a guest-dependent approach to tune the permanent porosity of the MOFs. In this approach, several tetraalkyammonium cations of different sizes were introduced into the channels by cation exchange to act as partitions and to support the main frameworks. This approach significantly enhanced the stability of the framework and its permanent porosity. Moreover, the gas-adsorption properties (such as gate sorption, hysteresis, and selectivity) of the MOFs were also modulated by the judicious choice of guest cations., (Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Published
2012
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