Pore-structure control in ultramicroporous porous coordination polymers for efficient selective capture of acetylene

Abstract

Physical adsorption separation of acetylene (C2H2) from carbon dioxide (CO2) on porous coordination polymers is a promising technique. However, it is still a particular challenge to realize the practical separation application of porous coordination polymers (PCPs) adsorbents with high separation performance, moderate adsorption heat, high stability and low cost. Herein, we demonstrate the efficient adsorption and separation of C2H2/CO2 from aspartate/malate anions columnar PCPs (namely PCPs-asp, PCPs-mal and PCPs-mal-n) exploiting the hydroxyl/amino sites within fine-tuning pore structures. Its one-dimensional (1D) chains and abundant hydroxyl/amino functional sites matched with target molecules, affording these anions columnar PCPs with not only high separation selectivity for C2H2/CO2, but also excellent gas capacity. Among them, PCPs-mal possesses an ultra-high C2H2 storage density of 655 g·L−1 under ambient conditions, and even close to the density of solid C2H2 at 189 K (729 g·L−1). PCPs-mal exhibits an IAST separation selectivity as high as 15.2 for the equimolar C2H2/CO2 binary mixture. The breakthrough experiments demonstrate that PCPs-mal realize efficient binary C2H2/CO2 separation with an acetylene dynamic adsorption capacity of 2.03 mmol·g−1. Theoretical calculations and GCMC simulations further provide critical insight into the separation mechanism at the molecular level. More importantly, the facile scaled synthesis, low adsorption enthalpy, and high separation performance make it cost-effective for real-world applications.