Facile and Clean Synthetic Route to Non-Layered Two-Dimensional ZIF-67 Nanosheets

Abstract

Two-dimensional (2D) metal organic framework (MOF) nanosheets (NSs) have recently gained considerable interest owing totheir structural advantages, such as large surface area and exposed active sites. Two different types of 2D MOF NSs have beenreported, including inherently layered MOFs and non-layered ones. Although several studies on inherently layered 2D MOFshave been reported, non-layered 2D MOFs have been rarely studied. This may be because the non-layered MOFs have a strongpreference to form three-dimensionality intrinsically. Furthermore, the non-layered MOFs are typically synthesized in thepresence of the surfactant or modulator, and thus developing facile and clean synthetic routes is highly pursued. In this study, afacile and clean synthetic methodology to grow non-layered 2D cobalt-based zeolitic imidazolate framework (ZIF-67) NSs issuggested, without using any surfactant and modulator at room temperature. This is achieved by directly converting ultrathinα-Co(OH)2 layered hydroxide salt (LHS) NSs into non-layered 2D ZIF-67 NSs. The comprehensive characterizations wereconducted to elucidate the conversion mechanism, structural information, thermal stability, and chemical composition of thenon-layered 2D ZIF-67. This facile and clean approach could produce a variety of non-layered 2D MOF NS families to extendpotential applications of MOF materials.