Sulfated zirconium metal-organic frameworks as highly efficient catalysts for the green synthesis of n-amyl acetate

To propose an environmentally friendly approach for the synthesis of n-amyl acetate, a sulfated zirconium-based metal-organic framework (MOF-808-SO4) with strong Br & Oslash;nsted-acidic character was synthesized and tested for the esterification of acetic acid with n-amyl alcohol. The catalysts were comprehensively characterized using a range of analytical techniques. The characterization results confirmed the successful incorporation of the sulfonic group onto MOF-808, and verified that the structural framework of MOF-808 remained intact after sulfuric acid treatment. MOF808-SO4 showed higher conversion of acetic acid than MOF-808, attributed to that MOF-808-SO4 showed higher acidity and greater number of Br & Oslash;nsted acid than MOF-808. Accordingly, the maximum conversion of acetic acid (91.3%) was achieved on MOF-808-SO4 under conditions of 2.0 wt% catalyst dosage, 2:1 alcohol/acid molar ratio at 120 degrees C for 5 h. The MOF-808-SO4 catalyst showed good recyclability, with the acetic acid conversion of 74.3% after four reaction cycles. Furthermore, the kinetic study demonstrated that the activation energy was determined to be 32.2 kJ/mol. Compared to other reported catalysts, MOF-808-SO4 demonstrated satisfactory activity, showing promising potential for the industrial production of esters from various alcohols and acetic acid mediated by heterogeneous acid catalysts.