Advancing Metal–Phenolic Networks for Visual Information Storage

We report a facile inking strategy for visual information storage (e.g., writing, printing, and beyond) via surface modification of substrates with polyphenols and subsequent in situ formation of metal–phenolic networks (MPNs) on the substrates. The reported technique has several advantages compared with current printing techniques. Diverse substrates can be used to fulfill the requirements for different applications (e.g., printing, writing, painting, and stamping). A range of colors (e.g., yellow, blue, and green) can be realized using different polyphenols (e.g., tannic acid, gallic acid, and pyrogallol) and metal ions (e.g., CuII, FeIII, and TiIV). The disadvantages (e.g., ink precipitation, color fading) associated with writing or printing using traditional ink can be overcome. The obtained paintings can be easily removed by acids enabling the recycling of substrates. The reported strategy provides a new avenue for the development of portable, nontoxic, and green technologies for writing, printing, and beyond, which expands the applications of MPN-based materials.