Hydrothermal preparation of hierarchical SAPO-34 constructed by nano-sheets using rapeseed pollen extract as water and its CO₂ adsorption property

Herein we report a biosynthesis route to prepare hierarchical SAPO-34 constructed by numerous nano-sheets. Rapeseed pollen extract was used as water to prepare the synthesis solution, which underwent hydrothermal synthesis to obtain the hierarchical SAPO-34. The product is characterized by XRD, FT-IR, SEM, N₂ adsorption-desorption and TG analysis. The hierarchical SAPO-34 shows a distinctive morphology with curly nano-sheets and gaps between nano-sheets, forming a blooming flower-like structure. Its specific surface area is 683 m² g^-1. The effect of the content of rapeseed pollen suspension was examined. Increasing in the content leads to the formation of the hierarchical SAPO-34 constructed with curlier and much more numbers of nano-sheets. The formation process of SAPO-34 was investigated and a possible formation mechanism was proposed. Such hierarchical SAPO-34 exhibits a high CO₂ adsorption capacity of 2.77 mmol/g at 100 kPa and the CO₂/CH₄ ideal separation factor of 8.2. It takes 6.1 min for CO₂ to reach the adsorption equilibrium, which is faster than that of conventional SAPO-34, possibly due to such nano-sheet-constructed fine structure.