Saturated Linkers in Two-Dimensional Covalent Organic Frameworks Boost Their Luminescence
Meijia Yang, Hiroki Hanayama, Long Fang, Matthew A. Addicoat, Yunyu Guo, Robert Graf, Koji Harano, Jun Kikkawa, Enquan Jin, Akimitsu Narita, Kläus Müllen
Abstract
High Resolution Image Download MS PowerPoint Slide The development of highly luminescent two-dimensional covalent organic frameworks (COFs) for sensing applications remains challenging. To suppress commonly observed photoluminescence quenching of COFs, we propose a strategy involving interrupting the intralayer conjugation and interlayer interactions using cyclohexane as the linker unit. By variation of the building block structures, imine-bonded COFs with various topologies and porosities are obtained. Experimental and theoretical analyses of these COFs disclose high crystallinity and large interlayer distances, demonstrating enhanced emission with record-high photoluminescence quantum yields of up to 57% in the solid state. The resulting cyclohexane-linked COF also exhibits excellent sensing performance for the trace recognition of Fe 3+ ions, explosive and toxic picric acid, and phenyl glyoxylic acid as metabolites. These findings inspire a facile and general strategy to develop highly emissive imine-bonded COFs for detecting various molecules.