Bottom-Up Fabrication of Ultrathin 2D Zr Metal–Organic Framework Nanosheets through a Facile Continuous Microdroplet Flow Reaction

Direct synthesis of the ultrathin and discrete 2D metal–organic framework (MOF) nanosheets is extremely challenging. Herein, we present the first facile continuous bottom-up strategy for preparing ultrathin (∼3 nm) 2D MOF nanosheets with high crystallinity comprising assemblies of a few layers. Unlike conventional solvothermal synthetic methods for 2D MOFs, the weak interlayer interaction in the vertical direction of the 2D materials is restricted under microdroplet flow reaction conditions. The 2D MOF nanosheets with a large lateral area and a few layers thick were directly synthesized by suppressing the lamellar stacking of the nanosheets under the dynamic growth conditions. The 2D MOF nanosheets were characterized by scanning and transmission electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy, powder X-ray diffraction, infrared spectroscopy, thermogravimetric analysis, gas adsorption, and light scattering techniques, which were supported by density functional theory (DFT) calculations and molecular simulations. The properties of the “as-prepared” 2D MOF nanosheets were compared with the corresponding pristine solvothermal MOF with extended structure perpendicular to the laminar assembly. The ultrathin 2D MOF nanosheets have greater external surface area, resulting in a far higher gas adsorption and colloidal suspensions that exhibit the Tyndall effect. This synthetic methodology for 2D MOF nanosheets has potential for scale-up of materials production.