Core-shell nanostructured heteropoly acid-functionalized metal-organic frameworks: Bifunctional heterogeneous catalyst for efficient biodiesel production

다국어 초록 (Multilingual Abstract)

<P><B>Abstract</B></P> <P>We developed a new class of acid-base bifunctional heterogeneous catalyst, which can be used in the transesterification of rapeseed oil for highly efficient biodiesel production. A simple Keggin-type HPA (heteropoly acid) functionalization on the surface of zeolitic imidazolate framework-8 (ZIF-8) nanoparticles, through an imidazolium medium, results in the bifunctional heterogeneous catalysts. The hybrid materials exhibit a novel hierarchically core-shell nanostructure, which provides a large surface area and interconnectivity, leading to a thin-wrinkled HPA shell at the surface of rhombic dodecahedral ZIF-8 core crystals. A strong ON hybrid bonding through an electrostatic effect in the hybrid materials demonstrates a strong interaction between the Keggin and imidazole units, which is one of the main driving forces of hybrid materials formation. Additionally, the transformation of the HPA/ZIF-8 ratio in the hybrid materials changes the acidity and basicity, thereby affecting catalyst activity. We used these bifunctional core-shell materials as environmentally friendly heterogeneous catalysts in the transesterification of rapeseed oil with methanol to produce a high-quality biodiesel. Of particular interest, the HPA-functionalized ZIF-8 catalyst with a proper HPA/ZIF-8 ratio shows a high FAME conversion of 98.02% along with high recyclability because of the sufficiently large surface area and bi-functionality of strong acidity. Furthermore, the HPA-functionalized ZIF-8 catalyst shows a high reaction efficiency of the benzyl alcohol oxidation process, indicating a great potential of our catalyst to a wide range of applications.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Bifunctional heterogeneous catalyst was prepared using HPA functionalization on ZIF-8 nanoparticles. </LI> <LI> HPA/ZIF-8 materials showed core-shell structure with large surface area and interconnectivity. </LI> <LI> A high FAME conversion of 98.02% along with high recyclability was obtained. </LI> <LI> A high reaction efficiency of the benzyl alcohol oxidation process was also achieved. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>The core-shell structured heteropoly acid (HPA)-functionalized zeolitic imidazolate frameworks-8 (ZIF-8) nanoparticles were used as acidic and basic bifunctional, highly-porous, heterogeneous catalysts for efficient biodiesel production.</P> <P>[DISPLAY OMISSION]</P>