(673e) Room-Temperature Synthesis of Functionalized Two-Dimensional Metal-Organic Frameworks for Enhanced CO2/CH4 Separation

Removal of CO₂ from raw natural gas is an essential process prior to the actual utilization of natural gas. Mixed-matrix membranes (MMMs) have showed advantages in CO₂/CH₄ separation, but great challenges exist in controlling the morphology and functionality of filler materials, which plays a key role in gas permeation and compatibility between filler materials and polymer matrix. Metal-organic frameworks (MOFs), due to their versatile synthetic procedures, exhibit tunable structures and chemical functionalities, and thus are good candidate for preparing MMMs. Herein, we demonstrated a one-step room-temperature synthesis of 2D MOFs based on Cu (II) paddle-wheel units with mixed ligands, where the intrinsically anisotropic building blocks led to the anisotropic growth of 2D MOF nanoparticles. This synthetic method was also successfully extended to preparing functionalized 2D MOFs by selecting ligands with different functional groups, with the thickness of the thinnest particles around 3 nm. To illustrate the advantage of using 2D MOFs in MMMs, the synthesized 2D MOFs were incorporated into polysulfone, a commercial polymer for CO₂/CH₄ separation, and the resultant MMMs exhibited improved CO₂/CH₄ separation performance with CO₂/CH₄ ideal selectivity increased by approximately 400% at 5 wt% loading of amino-functionalized 2D MOFs. Because the functionality of 2D MOFs can be readily tuned based on the selection of ligands, the presented strategy to prepare MMMs can be further extended to other energy and environment-related separations.