Thermodynamic and kinetic synergetic separation of CO2/C2H2 in an ultramicroporous metal-organic framework

Abstract

The selective removal of carbon dioxide (CO2) from acetylene (C2H2) is an important separation process in the petrochemical industry, but is challenging due to the similar physicochemical properties of the two gases. Using CO2-selective adsorbents that have preferential affinity for CO2 over C2H2 in pressure swing adsorption was deemed a promising separation method for the separation of CO2/C2H2 mixtures. Herein, we report an ultramicroporous metal-organic framework, Y-bptc, to achieve efficient separation of CO2/C2H2 through thermodynamic and kinetic synergetic effects. The unique cage-type structure interconnected by small windows exhibits high adsorption capacity for CO2 while efficiently impeding adsorption diffusion of C2H2, which was proved by the single-component equilibrium and kinetic adsorption curves. Grand canonical Monte Carlo (GCMC) molecular calculations further show that the µ3-OH− of the framework have a stronger adsorption affinity for CO2 through forming hydrogen bonds. Breakthrough experiments using Y-bptc as a CO2-selective adsorbent proved that high-purity C2H2 (>99%) could be directly produced from one-step separation of CO2/C2H2 (1/1, v/v) mixtures, which greatly reduced the separation process and energy consumption. In addition, the structure of Y-bptc due to the high charge density of the Y6 cluster has high stability under humid and high-temperature conditions adding to the application possibility in industry.