Metal–organic framework nanosheets: from nano-scale to micron-scale with tunable color

Abstract

Metal–organic framework nanosheets (MONs) are expected to turn the cornerstone of integrated electronic and optoelectronic devices owing to their unique properties. However, as the premise and guarantee for research applications, adjustable preparation and accurate control of MONs remain a challenge. Here in this work, we demonstrate that the sizes and colors of MONs can be tuned by subtle control of the solution pH (from 3 to 11) during the precursor preparation. Where the variation of the sizes of MONs from nano-scale (lateral size smaller than 200 nm) to micro-scale (lateral size larger than 10 μm) was achieved, which was accompanied by the continuous color variation from green to gray for the solid-state samples, and from orange to pink for the colloidal suspensions. As a result, linear correlations between the sizes and colors of the MONs with the solution pH were established. Laser irradiation experiments further demonstrated the inverse relationship between the fluorescence intensity of MONs and the pH, providing a fairly good strategy for the controlled preparation and color adjustment of MONs.