Zr-Based Metal-Organic Frameworks for Green Biodiesel Synthesis: A Minireview

Abstract

Metal-organic frameworks (MOFs) have widespread application prospects in the field of catalysis owing to their functionally adjustable metal sites and adjustable structure. In this minireview, we summarize the current advancements in zirconium-based metal-organic framework (Zr-based MOF) catalysts (including single Zr-based MOFs, modified Zr-based MOFs, and Zr-based MOF derivatives) for green biofuel synthesis. Additionally, the yields, conversions, and reusability of Zr-based MOF catalysts for the production of biodiesel are compared. Finally, the challenges and future prospects regarding Zr-based MOFs and their derivatives for catalytic application in the biorefinery field are highlighted.

Keywords: Zr-based MOFs; biofuels; esterification; heterogeneous catalysis; transesterification.

Figure 1

Various heterogeneous catalysts.

Figure 2

Schematic diagram of the structure and synthesis of UiO-66.

Figure 3

The suggested structures of UiO-66, UiO-66(COOH)₂, and UiO-66(NH₂).

Figure 4

Plausible mechanisms for esterification: (a) UiO-66 catalyst; (b) UiO-66-NH₂ acid–base catalyst. (Adapted with permission from Ref. [34]. Copyright 2015, Elsevier.)

Figure 5

The suggested structures for AIL and xAIL@NH₂-UiO-66 (where x indicates the mass ratio of AIL to NH₂-UiO-66).

Figure 6

Reaction mechanism of transesterification on mesoporous sulfated zirconia nanosheets. (Adapted with permission from Ref. [60]. Copyright 2020, Royal Society of Chemistry.)

Figure 7

SEM images for (a) HSiW@UiO-66, (b) HSiW@ZrO₂-300, (c) HSiW@ZrO₂-400, and (d) HSiW@ZrO₂-500. (Adapted with permission from Ref. [62]. Copyright 2021, open access from Royal Society of Chemistry.)