Facile Preparation of Mixed-Matrix Membrane for Highly Selective Separation of CO<sub>2</sub> via a Defected Zr-MOF Fluorination-Modified Strategy
Jiacheng Zhang, Xi Sun, Junhao Xin, Li Wang, Yong Fan, Jifu Zheng, Shenghai Li, Jianing Xu, Nanwen Li, Suobo Zhang
Abstract
To address increasing climate deterioration, it is of great value to prepare highly permselective separation membranes for CO 2 enrichment and separation. In this study, zirconium-based metal-organic frameworks (Zr-MOFs) containing defective structures (defected-UiO-66-NH 2, D-UN) with a high volume yield (12 g L –1 in a single batch) were prepared at room temperature for the first time using a simple green-synthesis strategy. After the modification with pentafluorobenzaldehyde, the fluorine-containing D-UN (named F- g -UN) nanoparticles showed the characteristics of local and dense distribution of fluorine elements. Due to the optimized CO 2 affinity and improved dispersion of fluorination modification, the prepared mixed-matrix membrane (MMM) F- g -UN@AO-PIM-1 achieved synergistic improvement in CO 2 permeability and selectivity, exceeding the 2008 Robeson upper bound (CO 2 664.1 Barrer and CO 2 /CH 4 34.2) and the 2018 binary CO 2 /CH 4 mixed-gas upper bound (CO 2 /CH 4 28.7). The substantial cause was the introduction of fluorine species, verified by relevant experiments and mechanism analyses such as CO 2 adsorption. This work proves the feasibility of using crystal defect engineering and post-treatment strategies to enhance separation functions and offers new insights into designing efficient and low-cost MMMs for gas separation, promoting their application in separation membranes including but not limited to gas separation.