Enhanced Catalytic Performance of a Membrane Microreactor by Immobilizing ZIF-8-Derived Nano-Ag via Ion Exchange

Abstract

A catalytic membrane microreactor (CMMR) was fabricated by immobilizing ZIF-8-derived nano-Ag in membrane pores via ion exchange. ZIF-8 was first in situ assembled in polyethersulfone (PES) membrane pores with polydopamine modification. The Zn–N bond disappeared and Ag–N bond appeared after ion exchange by a AgNO3 solution. Besides, the X-ray diffraction (XRD) characteristic peaks of ZIF-8 transformed into those of the Ag–MI coordination compounds. The Ag–N bond disappeared and the characteristic peaks of Ag appeared after reduction by a NaBH4 solution. It could be observed by transmission electron microscopy (TEM) that the size of nano-Ag was 4.55 ± 1.67 nm, which was one-fifth of that without ZIF-8 as a precursor. The inductively coupled plasma emission spectroscopy (ICP-OES) test revealed that the loading capacity of nano-Ag in PES membrane pores was 31.33%. The degradation of p-nitrophenol (p-NP) was applied to test the catalytic performance of the CMMR, and the apparent reaction rate constant could be increased by 2 orders of magnitude.