Fine-tuning of nano-traps in a stable metal–organic framework for highly efficient removal of propyne from propylene

Abstract

Despite tremendous efforts, precise control in the synthesis of porous materials with ideal nanocages for desired gas separation applications still remains a challenge. Microporous metal–organic frameworks (MOFs) have provided rich chemistry to enable precise control and design of structures, pore cavities, and functionalities at the molecular level. Here, we propose and design a microporous MOF (termed as ZJUT-1, ZJUT = Zhejiang University of Technology) with a fine-tuned nanocage, exhibiting the desired size, shape, and functionalities that are suitable for trapping a single propyne (C₃H₄) molecule. Adsorption and computational studies indicate that such optimized nanocages can not only reduce the uptake of propylene (C₃H₆), but also strengthen the C₃H₄–host interactions through multiple hydrogen-bonding between SiF₆²⁻/–NH₂ and C₃H₄ molecules. This material thus shows remarkably different C₃H₄ and C₃H₆ adsorption capacities, with the largest uptake ratio of 3.06 at 1 bar and 298 K, affording a very high selectivity (up to 70) for C₃H₄/C₃H₆ (1/99) separation. The actual breakthrough experiments demonstrate that ZJUT-1 can efficiently remove trace amounts of C₃H₄ from the important raw C₃H₄/C₃H₆ mixtures under ambient conditions with 0.19 mmol g⁻¹ C₃H₄ uptake capacity to produce 99.9995% pure C₃H₆.