Highly\nEmissive Covalent Organic Frameworks

Abstract

Highly luminescent\ncovalent organic frameworks (COFs) are rarely\nachieved because of the aggregation-caused quenching (ACQ) of π–π\nstacked layers. Here, we report a general strategy to design highly\nemissive COFs by introducing an aggregation-induced emission (AIE)\nmechanism. The integration of AIE-active units into the polygon vertices\nyields crystalline porous COFs with periodic π-stacked columnar\nAIE arrays. These columnar AIE π-arrays dominate the luminescence\nof the COFs, achieve exceptional quantum yield via a synergistic structural\nlocking effect of intralayer covalent bonding and interlayer noncovalent\nπ–π interactions and serve as a highly sensitive\nsensor to report ammonia down to sub ppm level. Our strategy breaks\nthrough the ACQ-based mechanistic limitations of COFs and opens a\nway to explore highly emissive COF materials.