Bimetallic zeolitic imidazolate frameworks (ZIFs) containing
two
different metal ions can exhibit superior performances when applied
in heterogeneous catalysis. Herein, we present a facile one-pot synthesis
method for PdCo-ZIFs with various Pd/Co ratios, where Pd(II) ions
are successfully incorporated into the Co node sites of the ZIF structure.
The local structure of the bimetallic ZIFs was comprehensively investigated
by pore-structure, X-ray absorption fine structure, and in situ CO
adsorption Fourier transform infrared analyses. The results demonstrated
that the framework comprises different coordination geometries of
Co (tetrahedral) and Pd (square planar) ions connected by the benzimidazolate
ligand. Notably, the inherently nonporous, 2D Co-ZIF structure was
transformed into a hierarchical porous structure, and the PdCo-ZIFs
exhibited a significantly increased concentration of defects and distorted
Co sites. Based on these results, the catalytic performances of the
synthesized ZIFs in the cycloaddition of CO2 to epoxides
were evaluated under a cocatalyst and solvent-free conditions. The
PdCo-ZIFs exhibited significantly higher catalytic activity (maximum
turnover frequency, TOF = 2501 h–1) than Co-ZIF
(TOF = 65 h–1) and Pd-ZIF (no activity), which revealed
that the undercoordinated Co sites with distorted structure are the
active sites rather than the incorporated Pd ions. This study provides
a facile one-pot method for synthesizing bimetallic ZIFs with mixed-coordination
modes, hierarchical porous structures, and modified defect concentrations,
which would expand the library of structurally diverse bimetallic
ZIFs toward various applications.
In recent years, Korea's shipbuilding industry have expanded its business into offshore plant. These changes are increasing the interest on job stress in shipbuilding industry. The purpose of this study is to investigate the differences of job stressors between white and blue-collar workers. The survey was using Korean Occupational Stress Scale(KOSS) questionnaire and was administered to 8,080 workers of large shipyard company. As a result of the survey, compared with the median score of Korean workers, job stress level of shipyard company workers was low. However, seven categories of KOSS, except for job demand showed higher stress levels of blue-collar workers than white-collar workers. The overall stress level of shipyard company workers is low, however, it is important to find stressors by considering the type of work, working period etc., through a detailed analysis of KOSS 8-categories. The results of this study may be helpful to identify the level of stress and to establish preventive measures in Shipyard Company.
Objective: The Work-related musculoskeletal disorders(WMSDs) have been a problem on industrial occupational safety and health in Korean shipyard industry. It has been a big social problem. Background: As a result, Korean government enacted a law to prevent musculoskeletal disorders at work and some major companies have already implemented an ergonomics program. Method: This paper presents a study on the effect of an ergonomics program in a Korean shipbuilding company during the last ten years. Conclusion: The Incidence of WMSDs, the worker's compensation cost and the lost time were decreased after implementation of the ergonomics program. Application: The results of the publishing will help efficient operation of MSDs prevention activity in other companies.
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