Synthesis of nano-crystal PVMo2W9@[Cu6O(TZI)3(H2O)6]4⋅nH2O for catalytically biodiesel preparation

To develop efficient and reusable catalysts for biodiesel production, quaternary heteropolyacid H 4 PVMo 2 W 9 O 40 (PVMo 2 W 9 ) was effectively wrapped inside rht -MOF-1 { rht -MOF-1 = [Cu 6 O(TZI) 3 (H 2 O) 6 ] 4 ⋅nH 2 O}, affording a crystalline H 4 PVMo 2 W 9 O 40 @ rht -MOF-1 ( 1 ) by one-pot hydrothermal method. The identification of the crystal structure of 1 was achieved through the utilization of X-ray crystallography. Nano-size crystals of 1 ( n-1 ) were prepared with the assistance of surfactant Tween 20. Notably, crystal n-1 was of cube shape grown along {100} facets rather than octahedral shape for 1 . When n-1 was applied as the catalyst for the esterification reactions, high conversion rates were achieved. E. g. about 97 % conversion for oleic acid to the corresponding monoalkyl esters and about 87 % for rapeseed oil to biodiesel. The catalyst was heterogeneous and recyclable 7 times without obvious attenuation. Further, the correlation between the catalytic activity and structure of n-1 was investigated in terms of the distribution of active sites, various pores in rht -MOF-1, and the accessibility of catalytic sites on the {100} facets.