Photocatalytic MOF membranes with two-dimensional heterostructure for the enhanced removal of agricultural pollutants in water

Agricultural pollutants, including pesticides in croplands and antibiotics in animal husbandry, have drawn widespread attention due to their toxicity, ubiquity and refractory. In this work, a photocatalytic MOF membrane with 2D heterostructure is developed to enhance the removal of agricultural pollutants in water through simultaneous interception and degradation. The 2D heterostructure is achieved via a vacuum-assisted self-assembly process in which ultrathin metal–organic framework (MOF-2) and graphitic carbon nitride (g-C3N4) nanosheets are alternately arranged to form orderly interlayer nanochannels. On one hand, the 2D heterostructure broadens the light-harvesting range and suppresses the recombination of photogenerated charge carriers by the energy level matching, thus improving the photocatalytic activity. On the other hand, the 2D heterostructure enforces the fluid confinement and steric-hindrance effect, which can expedite the radical attack and the pollutant interception, respectively. With the permeation flux of 23.6 L·m−2·h−1·bar−1, the 2D heterostructure membrane exhibits the enhanced removal rate towards agricultural pollutants (98% for ATZ, 95% for TC, 89% for SMT, and 92% for SMX). The removal mechanism is considered to be a combination of initial enrichment of pollutants, intensified photocatalytic degradation and electrostatic repulsion of by-products. Finally, the interlamellar attraction qualifies the 2D heterostructure membrane with stability and reusability over a wide range of pressure and pH, demonstrating good potential for long-term and high-efficient removal of agricultural pollutants in water quality security.