Preparation of macroporous transition metal hydroxide monoliths via a sol-gel process accompanied by phase separation

Three-dimensional transition metal hydroxide monoliths were facilely fabricated by a sol-gel process accompanied by phase separation in the presence of polyacrylic acid (PAA) and propylene oxide (PO). In the typical ZnCl₂-PAA-PO system, PAA is used as a phase separation inducer as well as a framework former to control the phase separation and the formation of macrostructures, whereas PO works as a proton scavenger to initiate the gelation of the system and freeze the macrostructures. Appropriate amount of PAA, PO and solvents allow the formation of zinc (Zn) hydroxide monolith with cocontinuous skeletons and interconnected macropores, and the construction mechanism and characteristics of macrostructure are also investigated. The resultant dried gels are amorphous Zn hydroxide monolith with a narrow macropore size distribution (~1 μm). This approach is further used to successfully prepare macroporous single or binary composite transition metal hydroxide monoliths.