In situ growth of the ZIF-8 on the polymer monolith via CO2-in-water HIPEs stabilized using metal oxide nanoparticles and its photocatalytic activity

Here, the ZnO/polyacrylamide (ZnO/PAM) macroporous composite monolith was first prepared through the radical polymerization of acrylamide in ZnO-costabilized CO 2 -in-water Pickering high internal phase emulsions (HIPEs). An efficient and green synthesis method was used to prepare the ZnO/PAM porous precursor materials, and ZnO nanoparticles (NPs) were used as a metal ion source to grow the metal organic frameworks (MOF) phase through secondary recrystallization, thereby synthesizing the target MOF/PAM porous monolith. The effects of the contents of ZnO NPs on the formation of HIPEs and properties of the target MOF/PAM composites for the photocatalytic degradation of cationic dye were studied. As the content of ZnO NPs increased to 3.75 wt%, the composite monolith had high mechanical stress (0.24 MPa) at 80% strain and recovered their shape. The as-synthesized ZIF-8/PAM composites were characterized using X-ray diffraction, scanning electron microscope (SEM), Brunauer Emmett Teller (BET), energy dispersive X-ray spectrometer (EDS) mapping, and TG methods. SEM images showed that the hybrid materials were interconnected, and the sizes of the open macropore and interconnected pore throats were 30–125 and about 2–20 μm, respectively. In addition, the ZIF-8/PAM material could be used as a high-efficiency photocatalyst to remove the cationic dye at a fast rate (88.6%).