Preparation of hierarchically porous spinel CoMn₂O₄ monoliths via sol–gel process accompanied by phase separation

Abstract

Cobalt manganite‐based hierarchically porous monoliths (HPMs) with three‐dimensionally (3D) interconnected macropores and open nanopores have been prepared via the sol–gel process accompanied by phase separation. The controlled hydrolysis and polycondensation of the brominated metal alkoxides, which are generated from an incomplete reaction between epichlorohydrin and MBr2 (M = Co and Mn) in N,N‐dimethylformamide (DMF), form a monolithic gel based on the two divalent metal cations. The dual‐polymer strategy using polyvinylpyrrolidone (PVP) and poly(ethylene oxide) (PEO) effectively induces the spinodal decomposition, where PVP and PEO are preferentially distributed to the gel phase and fluid phase, respectively, resulting in a porous gel characterized by the co‐continuous structure. The effects of DMF and PVP on the porous morphology derived from the phase separation have been systematically studied. Calcination of the as‐dried gels allows for the crystallization into the spinel phase yielding hierarchically porous CoMn2O4 monoliths, which have been examined in detail by the structural and compositional analyses.

Porous polymer‐derived ceramics: Flexible morphological and compositional controls through sol–gel chemistry

“…Furthermore, the ease of preparing an aqueous solution containing multiple elements affords porous monoliths with more complex compositions such as metal phosphates 164,227,228 and mixed metal oxides. 166,207,233,234 The family of porous monolithic materials prepared from inorganic salt precursors is still growing.…”

Synthesis of Hierarchically Porous Metal Oxide Monoliths via Sol–Gel Process Accompanied by Phase Separation From Divalent Metal Salts: A Short Review

“…To prove that the halogenated alkoxide route is also effective in the preparation of binary complex metal oxide, CoMn 2 O 4 HPM has been prepared (Lu et al, 2021). The spinel CoMn 2 O 4 HPMs were obtained after heat-treatment at above 300 °C in air (Figure 13A).…”