Toward quantitative evaluations of interfacial compatibility of ZIF-8 based mixed-matrix membranes via molecular simulations

Abstract

ZIF-8-based Mixed-Matrix Membranes (MMMs) have demonstrated promising potential for propylene/propane separation, but improvements in gas separation efficiency are hindered by the interfacial compatibility between ZIF-8 and the polymer matrix. In this study, we employed molecular modeling and simulations to construct and quantitatively compare the microstructural and energetic properties of three MMMs, including ZIF-8 with PIM-1, 6FDA-durene, and PIM-6FDA-OH. We assessed the applicability of the General Amber Force Field for modeling these MMMs and confirmed its validity. A protocol was developed to accurately define the interface region of the MMMs, ensuring reliability in calculating interfacial properties. Using this defined interface, we evaluated and compared the atomic concentration profile, interfacial length, polymer porosity, pore size distribution, and interfacial binding energy. Our findings indicate an order of interfacial compatibility as follows: ZIF-8/PIM-6FDA-OH > ZIF-8/6FDA-durene > ZIF-8/PIM-1, aligning well with literature reports. Further molecular-level analysis through radial distribution functions and dihedral angle distributions supported this compatibility order. Additionally, we explored the impact of modeling size on characterizing interfacial properties, affirming that our model effectively balances simulation accuracy and efficiency. Propylene/propane adsorption properties were also computed, revealing potential mechanisms for enhanced gas solubility in different MMMs. Most importantly, this comprehensive investigation led to the development and validation of an interface screening system, providing a reliable and efficient method for designing or screening polymer-filler pairs to improve gas separation performance.