Defect engineering of UiO-66 metal–organic frameworks offers promising opportunities to develop catalytic applications. Recently, the methanol conversion reaction has been used to quantitatively investigate the catalytic properties of defective UiO-66. In this contribution, the role of synthesis temperature in creating structural defects of UiO-66 was evaluated. First, the catalysts were synthesized using the solvothermal method at various temperatures (100–220 °C). The XRD, SEM-PSD, FTIR, TG-DTG, BET, TPD-NH3, and TPD-CO2 techniques were used to study the characteristics. The findings suggested that raising the synthesis temperature enhanced the crystallinity, surface area, thermal stability, and acidity of catalysts. Following that, activity tests were performed at P = 101.3 kPa and T = 300–450 °C, and increasing the reaction temperature improved the catalyst’s performance. As a result, UiO-66 produced at 220 °C had the best performance (conversion = 51 %, yield DME = 81 %), and its activity remained stable at 450 °C for 6 h.