One-step topochemical transformation of MoAlB into metastable Mo₂AlB₂ using a metal chloride salt reaction

Abstract

Reacting MoAlB with ZnCl2 at 550 ºC produces metastable Mo2AlB2 through a one-step topochemical transformation. This reaction showcases differences in reactivity between boride-based MAB phases and carbide-based MAX phases, which...

Soft Chemistry of Hard Materials: Low-Temperature Pathways to Bulk and Nanostructured Layered Metal Borides

“…We therefore anticipated that the reaction of MoAlB and ZnCl 2 may lead to the formation of a MBene but found that this reaction instead produced Mo 2 AlB 2 ! Specifically, we discovered that Mo 2 AlB 2 can be synthesized in a single step through a bulk-scale reaction between MoAlB and ZnCl 2 at 550 °C, where ZnCl 2 is molten (Figure a,c) . The reaction temperature is sufficiently high to crystallize Mo 2 AlB 2 directly under the conditions of Al deintercalation, which is facilitated by the ZnCl 2 etchant.…”

“…Panel (b) is adapted with permission from ref , copyright 2019 American Chemical Society. Panel (c) is adapted with permission from ref , copyright 2023 The Royal Society of Chemistry.…”

“…Specifically, we discovered that Mo 2 AlB 2 can be synthesized in a single step through a bulkscale reaction between MoAlB and ZnCl 2 at 550 °C, where ZnCl 2 is molten (Figure 6a,c). 48 The reaction temperature is sufficiently high to crystallize Mo 2 AlB 2 directly under the conditions of Al deintercalation, which is facilitated by the ZnCl 2 etchant. This reaction provides a streamlined synthesis of bulk metastable Mo 2 AlB 2 as well as an interesting case study in the different reactivities between MAX and MAB phases.…”

Atomic Scale Design of MXenes and Their Parent Materials─From Theoretical and Experimental Perspectives

“…However, this does not result in a layered material consisting of separated MXenes, but instead the material shrinks in the direction perpendicular to the MXene planes and collapses into a reconstructed bulk phase. There are also examples of materials with only partial etching of the A layer from MAB phases, − closely related to MAX phases, which is clearly not sufficient to comply with successful exfoliation, i.e., for the selective etching to be considered successful in relation to MXene synthesis, the A layer needs to be completely removed while avoiding the etched structure collapsing into a new bulk structure, i.e., the etched MAX phase should consist of chemically inert MXene substructures, not connected by chemical bonding.…”

Galvanic Replacement and Etching of MAX-Related Phases in Molten Salts toward MXenes: An In Situ Study

“…The resulting Ti 3 C 2 Cl z phase was further reacted with a molten Li 3 N/LiCl/KCl mixture to form N-termination groups. Finally, Baumler et al have also shown that molten-salt etching is feasible with boride compounds like MoAlB, although complete etching was not possible and the process was stopped at the Mo 2 AlB 2 phase.…”