Ultrathin 2D Coordination Polymer Nanosheets by Surfactant-Mediated Synthesis

Abstract

Low-dimensional nanostructures offer a host of intriguing properties which are distinct from those of the bulk material, owing to size-confinement effects and amplified surface areas. Here, we report on the scalable, bottom-up synthesis of ultrathin coordination polymer nanosheets via surfactant-mediated synthesis and subsequent exfoliation. Layers of a two-dimensional (2D) zinc coordination polymer are self-assembled in the interlamellar space of a reverse microemulsion mesophase into stacks of nanosheets interleaved with cethyltrimethylammonium bromide (CTAB) at regular intervals, thus giving rise to a lamellar hybrid mesostructure with a lattice period of ~8 nm and an underlying highly crystalline substructure. The basic structural motif is composed of 2D acetato-benzimidazolato-zinc layers of tetrahedrally coordinated zinc joined together by anionic acetate and benzimidazolate ligands. The hierarchical structure was studied by PXRD, TEM, EDX, EELS, AFM, and solid-state NMR spectroscopy, revealing a high level of order on both the atomic and mesoscale, suggesting fairly strong interactions along the organic-inorganic hybrid interface. Exfoliation of the hybrid material in organic solvents such as THF and chloroform yields sheet- and belt-like nanostructures with lateral sizes between 10's and 100's of nanometers and a height of about 10 nm measured by AFM, which precisely maps the basal spacing of the lamellar mesostructure; further exfoliation results in nanobelts with minimum sizes around 4 nm. Finally, the sheetlike nanostructures behave as morphological chameleons, transforming into highly regular multiwalled coordination polymer nanotubes upon treatment with organic solvents.

Multi-scale crystal engineering of metal organic frameworks

“…Similar rod-like morphologies have been obtained by Taylor et al [237,238] in reverse microemulsion systems for other metal-organic frameworks, such as In this latter case the microemulsion system was composed of CTAB as cationic surfactant, isooctane as the 'oil' phase, 1-hexanol as co-surfactant and water [26]. This approach was further extended to other coordination polymers by Lotsch and co-workers [235,239], who synthesized coordination polymer nanosheets composed of Zn, benzimidazole and acetate. In this case lamellar reverse microemulsions were prepared with CTAB, heptane, 1-hexanol and water and were used to confine the MOF growth into the interlamellar space.…”

“…These first findings on metal-cyanide framework nanoparticles prompted the use of similar reverse microemulsion systems to tune the particle size and/or shape of other Prussian blue analogues, such as K [230][231][232], and metal-organic frameworks [184,[233][234][235][236].…”

Lanthanide-based metal-organic framework nanosheets with unique fluorescence quenching properties for two-color intracellular adenosine imaging in living cells

“…Very recently, 2D metal-organic framework (MOF) thin films or nanosheets have been successfully synthesized and exfoliated by several groups. [8][9][10] Their potential biological applications remain to be explored.MOFs are a fascinating class of functional materials that have been extensively studied for applications in gas storage, 11 catalysis, 12 separation 13 and sensing. 14 MOFs are certainly very promising for fabricating multifunctional luminescent sensors, because both the metal and the ligand units can provide platforms for generating luminescence and some guest molecules loaded on the MOFs can also emit or induce luminescence.…”

“…Very recently, 2D metal-organic framework (MOF) thin films or nanosheets have been successfully synthesized and exfoliated by several groups. [8][9][10] Their potential biological applications remain to be explored.…”

Manganese oxide nanosheets and a 2D hybrid of graphene–manganese oxide nanosheets synthesized by liquid-phase exfoliation

“…4,[52][53][54] As shown in Figures S10a to S10c, during ultrason-ication numerous MON were produced and typically lay around MOFN cores that appeared to be "unraveled". This view is supported by the fact that the typical size of the resulting MON was 20-40 nm, approximately the same size of the"petals" of the MOFN shown in Figure 1c.…”