Rapid synthesis of metal-organic framework CALF-20 in H2O/methanol solution under room temperature and normal pressure

In this study, a new process to synthesize Calgary framework 20 (CALF-20), a zinc-based metal-organic framework (MOF), in a H2O/methanol solution was developed, exhibiting a high CO2 adsorption capacity. Generally, CALF-20 was synthesized by a solvothermal method, requiring the consumption of considerable thermal energy. On the other hand, the proposed synthetic process required only 6 min to crystallize CALF-20 in a H2O/methanol mixed solution at room temperature (298 K) and normal pressure (101.3 kPa). In addition, CALF-20 was obtained in 93.3% yield using zinc and oxalate sources under an aging time of 120 min. As-synthesized CALF-20 exhibited a Brunauer–Emmett–Teller surface area of 520 m2 g−1, a micropore volume of 0.19 cm3 g−1, a CO2 uptake of 3.84 mmol g−1 at 298 K, and a PCO2 of 100 kPa; these values were similar to those obtained for CALF-20 synthesized by the solvothermal method using high thermal energy. Furthermore, CALF-20 was crystallized without washing using H2O. The key factor for the crystallization of the CALF-20 structure in this process was the deprotonation of 1,2,4-triazole, which was caused by the acetate anion derived from zinc acetate as the starting metal source.