Dynamic two-dimensional covalent organic frameworks.

Porous covalent organic frameworks (COFs) enable the realization of functional materials with molecular precision. Past research has typically focused on generating rigid frameworks where structural and optoelectronic properties are static. Here we report dynamic two-dimensional (2D) COFs that can open and close their pores upon uptake or removal of guests while retaining their crystalline long-range order.

Electrically Conductive Carbazole and Thienoisoindigo-Based COFs Showing Fast and Stable Electrochromism.

Thienothiophene thienoisoindigo (ttTII)-based covalent organic frameworks (COFs) have been shown to offer low band gaps and intriguing optical and electrochromic properties. So far, only one tetragonal thienothiophene thienoisoindigo-based COF has been reported showing stable and fast electrochromism and good coloration efficiencies. We have developed two novel COFs using this versatile and nearly linear ttTII building block in a tetragonal and a hexagonal framework geometry to demonstrate their attractive features for optoelectronic applications of thienoisoindigo-based COFs.

Selective functionalization of the 1-imidazo[1,2-]pyrazole scaffold. A new potential non-classical isostere of indole and a precursor of push-pull dyes.

We report the selective functionalization of the 1-imidazo[1,2-]pyrazole scaffold using a Br/Mg-exchange, as well as regioselective magnesiations and zincations with TMP-bases (TMP = 2,2,6,6-tetramethylpiperidyl), followed by trapping reactions with various electrophiles. In addition, we report a fragmentation of the pyrazole ring, giving access to push-pull dyes with a proaromatic (1,3-dihydro-2-imidazol-2-ylidene)malononitrile core. These functionalization methods were used in the synthesis of an isostere of the indolyl drug pruvanserin.

Fast-Switching Vis-IR Electrochromic Covalent Organic Frameworks.

Electrochromic coatings are promising for applications in smart windows or energy-efficient optical displays. However, classical inorganic electrochromic materials such as WO suffer from low coloration efficiency and slow switching speed. We have developed highly efficient and fast-switching electrochromic thin films based on fully organic, porous covalent organic frameworks (COFs).

Perylene-Based Covalent Organic Frameworks for Acid Vapor Sensing.

Traditionally, the properties and functions of covalent organic frameworks (COFs) are defined by their constituting building blocks, while the chemical bonds that connect the individual subunits have not attracted much attention as functional components of the final material. We have developed a new series of dual-pore perylene-based COFs and demonstrated that their imine bonds can be protonated reversibly, causing significant protonation-induced color shifts toward the near-infrared, while the structure and crystallinity of the frameworks are fully retained. Thin films of these COFs are highly sensitive colorimetric acid vapor sensors with a detection limit as low as 35 μg L and a response range of at least 4 orders of magnitude.