A zirconium-based microporous metal–organic framework for molecular sieving CO2 separation

Abstract

The decarbonization processes involved in the purification of natural gas and post-combustion CO₂ capture from flue gas are significantly important for the chemical industry and neutralization of carbon emissions. Physisorption-based gas separation using solid sorbents for exclusively capturing carbon dioxide, namely molecular sieving, is an excellent strategy for achieving superior separation efficiency compared to conventional energy-intensive methods. Herein, a zirconium-based microporous metal–organic framework, constructed from a low-cost ligand, formic acid, termed Zr-FA, showed excellent performance in the selective separation of carbon dioxide from methane and nitrogen. Zr-FA completely separates CO₂ from CH₄ and N₂ with high selectivity and a high carbon capture uptake of 72.4 cm³ cm⁻³ at ambient conditions. The narrow pore size of Zr-FA (∼3.4 Å) is the determining factor for molecular sieving carbon dioxide separation, which prohibited the diffusion of CH₄ and N₂. Molecular simulation studies found that the CO₂ molecules are bound within Zr-FA through electrostatic and weak hydrogen bonding interactions from the formic acid ligands. Practical breakthrough experiments were also conducted in a Zr-FA filled column, in which significant carbon dioxide capturing productivity in CO₂/CH₄ and CO₂/N₂ gases mixtures of 1643 mmol L⁻¹ and 1478 mmol L⁻¹ were demonstrated. This outstanding molecular sieving CO₂ separation performance indicated the significant potential of Zr-FA adsorbents for practical carbon capture and storage (CCS) applications.