Pebax mixed matrix membranes based on novel HOF/MOF nanofiller with simultaneous improvement in CO2 permeability and CO2/N2 selectivity

Abstract

The functionalized modification of metal–organic frameworks (MOFs) has become an emerging strategy to enhance the gas separation performance of mixed matrix membranes (MMMs). In the current study, Cu-MOF with regular spherical morphology was developed, and then a spherical Cu-MOF/HOF composite filler was successfully prepared by growing a hydrogen-bonded organic framework (HOF-21) with Cu²⁺ as an anchor point and dispersed in a Pebax 1657 matrix to create high-performance MMMs. According to the proposed etching/competition-repair mechanism, HOF-21 modification significantly increased the BET surface area of Cu-MOF/HOF(15) (133.4 m² g⁻¹, a 168.7% enhancement compared to Cu-MOF), while narrowing the pore size distribution. This structural advantage enabled Pebax-Cu-MOF/HOF(15) membranes containing 3.5 wt% fillers to exhibit excellent CO₂ permeability (129.2 Barrer) and CO₂/N₂ selectivity (75.33) at 25 °C and 6 bar, exceeding the 2008 Robeson upper bound. The proposed novel functionalization method, based on the sequential growth of HOF on MOFs, is simple and effective, and can be easily extended to other MOF functionalization systems with the aim of developing advanced nanofillers for MMMs.