Topochemical Synthesis of Monometallic (Co2+–Co3+) Layered Double Hydroxide and Its Exfoliation into Positively Charged Co(OH)2 Nanosheets

From platelets to sheets: A topochemical phase conversion employing bromine in acetonitrile transforms β-Co(OH)2 into monometallic Co2+–Co3+ layered double hydroxide (LDH) with a Co2+/Co3+ ratio of 2:1 (see the elemental maps of Co, Br, and O in a Br−-intercalated Co2+–Co3+ LDH platelet). Further treatment allows exfoliation of Co2+–Co3+ LDH into positively charged Co(OH)2 nanosheets. Scale bars: 2 μm.