TY - JOUR
T1 - Structural engineering of Zr-based metal-organic framework catalysts for optimized biofuel additives production
AU - Jrad, Asmaa
AU - Hmadeh, Mohamad
AU - Abu Tarboush, Belal J.
AU - Awada, Ghadir
AU - Ahmad, Mohammad
N1 - Funding Information:
The authors gratefully acknowledge the funding provided by the American University of Beirut Research Board and the K. Shair Central Research Science Laboratory. MH acknowledges the CNRS - AUB for funding (number 103496 and 103487 ).
Funding Information:
The authors gratefully acknowledge the funding provided by the American University of Beirut Research Board and the K. Shair Central Research Science Laboratory. MH acknowledges the CNRS-AUB for funding (number 103496 and 103487).
Publisher Copyright:
© 2019 Elsevier B.V.
PY - 2020/2/15
Y1 - 2020/2/15
N2 - This study reports the first investigation of the systematic introduction of defects in functionalized UiO-66 structures and its effect on their catalytic activities. Indeed, fifteen UiO-66-based MOFs were synthesized and used as catalysts in the esterification reaction of butyric acid in presence of butanol to produce the novel green biofuel additive, butyl butyrate. The samples included three different structures, UiO-66, UiO-66(COOH)2, and UiO-66(NH2), and five different modulation synthesis conditions for each structure yielding a total of fifteen samples. The increase in the modulator acidity or concentration significantly increased the number of missing linkers per cluster, surface area, and pore volume of the three structures. This leads to the increase in the conversion to butyl butyrate to levels higher than those previously achieved with similar systems. The improved conversion in each structure was attributed to the missing-linker defective sites which act as catalytic centers for the activation of butyric acid. However, using organic linkers with uncoordinated Brønsted acid sites boosted the catalytic activity of UiO-66(COOH)2 to levels higher than both counterparts even for lower number of defects, surface area, and pore size. The catalytic reaction was thus proved to be occurring utilizing both the defective sites and the carboxylic functional groups as catalytic centers and a reaction mechanism is proposed based on this assumption. Finally, the choice of the organic linker for the engineering of the MOFs' structure in catalytic applications offers abundant possibilities especially if coupled with the systematic increase in defective sites to overcome challenging diffusion limitations.
AB - This study reports the first investigation of the systematic introduction of defects in functionalized UiO-66 structures and its effect on their catalytic activities. Indeed, fifteen UiO-66-based MOFs were synthesized and used as catalysts in the esterification reaction of butyric acid in presence of butanol to produce the novel green biofuel additive, butyl butyrate. The samples included three different structures, UiO-66, UiO-66(COOH)2, and UiO-66(NH2), and five different modulation synthesis conditions for each structure yielding a total of fifteen samples. The increase in the modulator acidity or concentration significantly increased the number of missing linkers per cluster, surface area, and pore volume of the three structures. This leads to the increase in the conversion to butyl butyrate to levels higher than those previously achieved with similar systems. The improved conversion in each structure was attributed to the missing-linker defective sites which act as catalytic centers for the activation of butyric acid. However, using organic linkers with uncoordinated Brønsted acid sites boosted the catalytic activity of UiO-66(COOH)2 to levels higher than both counterparts even for lower number of defects, surface area, and pore size. The catalytic reaction was thus proved to be occurring utilizing both the defective sites and the carboxylic functional groups as catalytic centers and a reaction mechanism is proposed based on this assumption. Finally, the choice of the organic linker for the engineering of the MOFs' structure in catalytic applications offers abundant possibilities especially if coupled with the systematic increase in defective sites to overcome challenging diffusion limitations.
KW - Biofuel additives
KW - Brønsted acid
KW - Heterogeneous catalysis
KW - Metal-organic framework
KW - Structural defects
UR - http://www.scopus.com/inward/record.url?scp=85072962495&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85072962495&partnerID=8YFLogxK
U2 - 10.1016/j.cej.2019.122793
DO - 10.1016/j.cej.2019.122793
M3 - Article
AN - SCOPUS:85072962495
SN - 1385-8947
VL - 382
JO - Chemical Engineering Journal
JF - Chemical Engineering Journal
M1 - 122793
ER -