Heterostructure engineered membranes based on two-dimensional bimetallic MOF for enhanced remediation of dye contaminated wastewater

As a heterogeneous Fenton-like catalyst, two-dimensional (2D) bimetallic MOF can be readily engineered into lamellar membranes which integrate precise separation and Fenton-like degradation to enhance the elimination of organic contaminants from wastewater by rational design of interlayer spacing and constituent units. In this work, a 2D FeNi-MOF is assembled with ultrathin graphitic carbon nitride (g-C3N4) spacers into heterostructure membranes for enhanced remediation of dye contaminated wastewater by synergistic promotion of membrane separation and Fenton-like processes. For the establishment of heterostructure, FeNi-MOF and g-C3N4 nanosheets are alternately arranged by the coordination bonds between bimetallic nodes and pyridinic N to create orderly laminar nanochannels. On the one hand, the heterostructure provides abundant water passages and fixes the membrane interlayer distance to 1.0–1.2 nm with the permeation flux of 47.8–110.1 L m2 h−1·bar−1. On the other hand, the heterostructure can act as the Fenton-like mediator to expedite the cycle efficiency of Fe(III)/Fe(II) and Ni(II)/Ni(III). The synergistic promotion mechanism of membrane separation and Fenton-like processes is elaborated by simulating the molecular transport peculiarity through membrane nanochannels and the electron transfer efficiency between dual active centers. The contaminant molecules are trapped within the membrane by specific or non-specific channel-guest interaction with heterostructure nanochannels while the steadily generated radicals attack and degrade the confined contaminants, reaching the dye removal rate of approximately 99.0%. Anchoring between adjacent layers and bimetallic cycle reaction in confined fluid confer the stability and recyclability to the heterostructure membrane under wide-range pH and pressures, which are promising for the sustainable treatment of dye contaminated wastewater.