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

• Published in: Journal of the American Ceramic Society Vol. 104; no. 6; pp. 2449 - 2459
• Main Authors: Lu, Xuanming, Kanamori, Kazuyoshi, Hasegawa, George, Nakanishi, Kazuki
• Format: Journal Article
• Language: English
• Published: Columbus Wiley Subscription Services, Inc 01.06.2021
• Subjects: 3D interconnected macropores; Alkoxides; Bromination; Cationic polymerization; Cobalt compounds; cobalt manganite; Crystallization; Dimethylformamide; Epichlorohydrin; Ethylene oxide; Gels; hierarchically porous monolith; Morphology; Phase separation; Polyethylene oxide; Polyvinylpyrrolidone; Porosity; Sol-gel processes; sol–gel process; Spinel; Spinodal decomposition
• DOI: 10.1111/jace.17662
• ISSN: 0002-7820

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. The hierarchically porous cobalt manganite monoliths were prepared via sol–gel process accompanied by phase separation. The crystalline CoMn2O4 can be obtained after heat‐treatment in air without losing its hierarchical pores.