“…The density of oxygen-containing functional groups on GO plays a crucial role in the fabrication of dense, continuous, uniform, and thin ZIF-8 membranes. Because GO is a two-dimensional material with oxygen-containing functional groups, it is considered a good template to grow nanosized materials, as precursors bind to the oxygen-containing functional groups. , However, because most oxygen-containing functional groups are located at the edge sites of GO, , the large-flake GO synthesized using the conventional Hummer’s method has few oxygen-containing functional groups, resulting in the sparse growth of ZIF-8 crystals. Thus, we controlled the size of the GO flakes (and consequently the density of functional groups) through a simple and scalable horn sonication method. , …”