Flow Synthesis of Ni–BDC: Effects of Flow Rate and Temperature on Yield and Apparent Crystallinity

Abstract

Nickel terephthalate (Ni–BDC) was synthesized in a sonicated coiled-tubing flow reactor to examine the effects of flow rate and temperature on isolated yield and apparent crystallinity. A solvothermal product prepared at 140 °C for 12 h was used as the reference. Flow synthesis was evaluated at 0.10, 0.20, and 0.40 mL min⁻¹ at 75 °C, followed by temperature variation from 70 to 80 °C at 0.20 mL min⁻¹. Product formation was assessed by powder X-ray diffraction and Fourier-transform infrared spectroscopy, while isolated yield and apparent crystallinity were compared. Increasing flow rate from 0.10 to 0.40 mL min⁻¹ reduced yield from 60.76% to 42.78% and apparent crystallinity from 18.54% to 11.39%. At 0.20 mL min⁻¹, increasing temperature raised yield from 29.22% at 70 °C to 72.66% at 80 °C; apparent crystallinity at 80 °C reached 25.26%. Two independently synthesized batches prepared at 80 °C and 0.20 mL min⁻¹ showed close qualitative agreement in their PXRD profiles. Compared with the solvothermal route, the flow condition operated at a temperature 60 °C lower and required approximately one-quarter of the processing time while providing higher yield and comparable apparent crystallinity. These results support the feasibility and qualitative reproducibility of the investigated flow synthesis procedure.