Two AIE-Ligand-Based 2-D Luminescent Metal-Organic Frameworks as Fe 3+ Sensors.

The design and synthesis of high-performance sensors are very important but remain great challenges. In this work, a new aggregation-induced-emission (AIE) molecule 4,4'-(((9 H -fluoren-9-ylidene)methylene)bis(4,1-phenylene))dipyridine ( L ) was successfully synthesized and first developed as a functional ligand to construct two isomorphic metal-organic frameworks (MOFs) [M( L )(OBBA)] n [M 2+ = Cd 2+ ( 1 ), Co 2+ ( 2 ); H 2 OBBA = 4,4'-oxybisbenzoic acid]. They adopt [M 2 (COO) 4 ] flywheel clusters, OBBA 2- bridges, and terminal L ligands as building units to form isomorphic 2-D networks with Lewis base active cites (uncoordinated pyridyl N). Both 1 and 2 exhibit excellent water, pH, and thermal stabilities and extremely efficient Fe 3+ sensing abilities in the water environment. The quenching constants and detection limits reach the best levels reported so far. The sensing mechanism of 1 and 2 toward Fe 3+ is studied in depth, and the difference in their sensing performance is also explained.