UV-triggered fast assembly of a high-performing stable enzyme@MOF composite membrane for efficient aquatic micropollutants removal

As conventional water purification technologies are inefficient, they put us at risk of exposure to emerging micropollutants. Here, we report a two-step method for rapid construction of a stable enzyme@MOF biomimetic membrane comprising enzyme-embedded metal–organic framework-based biocomposites for continuous and efficient removal of micropollutants from water. We first prepared a horseradish peroxidase@zeolitic imidazolate framework-8 (HRP@ZIF-8) biocomposite via ball-milling method, capable of preserving structural integrity and the entrapped enzyme bioactivity under different denaturing environments. The second step involves biocomposite membrane synthesis via stimulation of polydopamine (PDA) polymerization with UV light after successively dispersing the dopamine and HRP@ZIF-8 biocomposite molecules in a neutral pH Tris-HCl system. Accompanied by the clever codeposition with PDA, the HRP@ZIF-8 biocomposite can be “sandwiched” between the PDA layers to create a stable HRP@ZIF-8-composite membrane (HRP@ZIF-8-CM). HRP@ZIF-8-CM synergistically integrates MOF adsorption, enzyme catalysis, and membrane separation functions. The calculated encapsulation rate of the HRP@ZIF-8 biocomposite is ≤ 98.2 %. The enzyme@MOF composite membrane has a catalytic degradation efficiency of 98 % for bisphenol A (1 mg/L), membrane water flux of 32.3 L/m 2 h bar, outstanding stability, and high efficiency after 7 cycles of use. Surprisingly, the bisphenol A removal rate of the enzyme@MOF composite membrane remained stable under varying denaturing conditions, including wide pH and temperature ranges and proteolytic enzymes, indicating that HRP enzyme activity is well preserved, probably owing to the bio-inertness of ZIF-8. In conclusion, we propose a new, simple, and fast method for the constructing enzyme@MOF composite membranes, which can significantly improve water purification.