A new aminobenzoate-substituted s-triazin-based Zr metal organic frameworks as efficient catalyst for biodiesel production from microalgal lipids

In order to solve problems that large molecules of microalgal lipids were difficult to access active sites in micropore structures of traditional metal organic frameworks (MOF), a novel two-dimensional nanosheet catalyst (aminobenzoate-substituted s-triazin-based Zr metal organic frameworks, Zr-TATAB) that exposed more active sites with stronger acidity was synthesized through replacement of trimesate linker in water/acid-resistant Zr-based MOF-808 with 4,4 ́,4 ́ ́- s -triazine-1,3,5-triyltri- p -aminobenzoate (H 3 TATAB) to promote catalytic conversion efficiency of microalgal lipids to biodiesel . The binding energy of Zr increased by 0.2 eV due to electronic shift caused by triazine ring and imine groups in H 3 TATAB ligand, which led to more exposed Zr 4+ active sites in Zr-TATAB catalyst. Due to increase of charge on crystal edges, dissociation of terminal hydroxyl groups was inhibited and Coulomb repulsion was increased. Therefore, Zr-TATAB catalyst possessed higher dispersion to avoid from pore blocking and catalytic deactivation, which enhanced recycling performance of catalyst. Compared with MOF-808, the total number of acid and base sites in Zr-TATAB catalyst increased from 6.0 mmol g −1 to 8.0 mmol g −1 , while strength of acid sites increased with an increased ammonia desorption temperature by 150 °C, which led to an increased catalytic conversion efficiency of microalgal lipids to biodiesel to 98.2%.