Constructing a highly permeable bioinspired rigid-flexible coupled membrane with a high content of spindle-type MOF: efficient adsorption separation of water-soluble pollutants

Abstract

In recent years, metal–organic frameworks (MOFs) have emerged as a crucial component in the design and fabrication of advanced adsorption separation membranes. The inherent rigidity of these MOF membranes, however, has limited their potential applications in the field of separation technologies. To address these limitations, MOF hybrid membranes have been developed incorporating flexible guest materials. Nevertheless, the proliferation of guest materials has imposed constraints on the advantages inherent to MOFs, and the interactions between these flexible guest materials and MOFs have impeded the progress of MOF membrane technology. Drawing inspiration from the “brick and mortar” structure characteristic of nacre, this study proposed the creation of a rigid-flexible coupled membrane. This innovative approach utilizes a spindle-type MOF as the rigid framework, graphene oxide (GO) as the flexible interlinking component, and tannic acid (TA) as the cross-linking agent. The synthesized coupled membranes (CoFe-MOF/GO–TA) demonstrated exceptional separation efficacy (>98.10%, 210–296 L m⁻² h⁻¹ bar⁻¹) and exhibited outstanding cycling stability in the removal of water-soluble pollutants. Remarkably, after 16 cycles, the permeance to rhodamine B (RhB) was recorded at 230.11 L m⁻² h⁻¹ bar⁻¹, with a rejection of 97.26%, underscoring the superior cycling stability of the MOF hybrid membrane. At the molecular level, the degradation mechanism of RhB was elucidated through a series of experiments and Gaussian calculations, validating the potential of MOFs in pollutant degradation. This discovery provided substantial support for the use of MOFs in the catalytic purification of membranes. Additionally, the MOF hybrid membranes exhibited comparably excellent separation capabilities for both antibiotics and dyes. The bioinspired rigid-flexible coupled membrane demonstrated a synergistic advantage, significantly enhancing the development of MOF hybrid membranes with superior separation performance and remarkable cycling stability.