Redox-triggered switching in three-dimensional covalent organic frameworks

Abstract

The tuning of molecular switches in solid state toward stimuli-responsive materials has attracted more and more attention in recent years. Herein, we report a switchable three-dimensional covalent organic framework (3D COF), which can undergo a reversible transformation through a hydroquinone/quinone redox reaction while retaining the crystallinity and porosity. Our results clearly show that the switching process gradually happened through the COF framework, with an almost quantitative conversion yield. In addition, the redox-triggered transformation will form different functional groups on the pore surface and modify the shape of pore channel, which can result in tunable gas separation property. This study strongly demonstrates 3D COFs can provide robust platforms for efficient tuning of molecular switches in solid state. More importantly, switching of these moieties in 3D COFs can remarkably modify the internal pore environment, which will thus enable the resulting materials with interesting stimuli-responsive properties.

Guest‐Driven Light‐Induced Spin Change in an Azobenzene Loaded Metal–Organic Framework

“…Stimuli‐responsive materials, [1–3] which can reversibly change their structures and properties in response to external stimuli such as light, [4–6] pH, [7, 8] chemicals, [9, 10] and heat, [11] have attracted tremendous attention due to their potential applications in drug delivery, [12, 13] smart windows, [14] molecular machines, [15] etc. Compared to the other external stimuli, light irradiation is of particular interest owing to its simple, handy and non‐invasive stimulus and has been frequently used in a variety of multi‐functional systems [16–20] …”

Guest‐Driven Light‐Induced Spin Change in an Azobenzene Loaded Metal–Organic Framework

“…Stimuli-responsive materials, [1][2][3] which can reversibly change their structures and properties in response to external stimuli such as light, [4][5][6] pH, [7,8] chemicals, [9,10] and heat, [11] have attracted tremendous attention due to their potential applications in drug delivery, [12,13] smart windows, [14] molecular machines, [15] etc. Compared to the other external stimuli, light irradiation is of particular interest owing to its simple, handy and non-invasive stimulus and has been frequently used in av ariety of multi-functional systems.…”

3D Hydrazone‐Functionalized Covalent Organic Frameworks as pH‐Triggered Rotary Switches

“…[6] For example, we have acquired a series of 3D functionalized COFs, [7] for example, 3D tetrathiafulvalene-based COFs for tunable electrical conductivity, 3D carboxy-functionalized COF for selective ion adsorption, and 3D Salphen-based COFs as catalytic antioxidants. Despite the aforementioned efforts in the in-situ synthesis and post-synthesis modifications, the functionalization of 3D COFs still remains largely undeveloped up to now, especially 3D architectures with stimuli-responsive functions, [8] due to the lacking of building units, the difficulty of directional synthesis, and the sophisticated procedure for introducing functional groups into the framework.It is well-known that hydrazone and its derivatives are significant synthons for numerous transformations, and their CN groups can undergo efficiently reversible structures betweenThe property expansion of 3D functionalized covalent organic frameworks (COFs) is important for developing their potential applications. Herein, the first case of 3D hydrazone-decorated COFs as pH-triggered molecular switches is reported, and their application in the stimuli-responsive drug delivery system is explored.…”

“…[6] For example, we have acquired a series of 3D functionalized COFs, [7] for example, 3D tetrathiafulvalene-based COFs for tunable electrical conductivity, 3D carboxy-functionalized COF for selective ion adsorption, and 3D Salphen-based COFs as catalytic antioxidants. Despite the aforementioned efforts in the in-situ synthesis and post-synthesis modifications, the functionalization of 3D COFs still remains largely undeveloped up to now, especially 3D architectures with stimuli-responsive functions, [8] due to the lacking of building units, the difficulty of directional synthesis, and the sophisticated procedure for introducing functional groups into the framework.…”