Observation of ZnO nanoparticles outside pores of nano Zn4O(C8H4O4)3 metal–organic framework

It was recognized that ZnO can be formed during synthesizing nano Zn4O(C8H4O4)3 metal–organic framework (nano MOF-5). Furthermore, it is generally accepted that the ZnO is dispersed inside the pores of MOF-5. However, herein, the measurements of X-ray powder diffraction (XRD) and transmission electron microscopy (TEM) showed that the crystal particle sizes of ZnO in MOF-5 are in the range of 5–18 nm, which are larger than the pore size of MOF-5 (1.3 nm). This clearly demonstrates that those ZnO nanoparticles are located outside the pores of MOF-5.

Research highlights
► Nano Zn4O(C8H4O4)3 framework (MOF-5) was synthesized.
► Nano-crystal ZnO particles (5–18 nm) were formed in synthesis of nano MOF-5.
► The nano-crystal ZnO particles were located outside the pores of MOF-5.