Luminescence modulation by twisting the branches of organic building blocks in uranyl-organic frameworks

Abstract

Twisting the branches of an organic molecule will enhance luminescence; however, this is often accompanied by the rotation of the branches that will reduce luminescence, offering a contradiction. Thus, deep insight into this contradiction and creating some effective solutions to make a good trade-off have become critical but challenging. Here, we report a smart structural design to fine-tune the twisting of the branches of triangular organic building blocks through steric hindrance, including anchoring of organic units or further construction of uranyl-organic metal-organic frameworks (U-MOFs). Both theoretical calculations and experimental results disclose that the fluorescence performance in the solid for both organic ligands and corresponding U-MOFs highly correlates with the twisting of the branches, and both the anchoring of organic units and the construction of U-MOFs would be effective tools to modulate the trade-off between twisting and rotation, and that rotation could play a key role in promoting a turn-on antenna effect. • The relationship between twisting and rotation is disclosed in U-MOFs • Adjusting steric hindrance gives a trade-off between twisting and rotation • Luminescence in U-MOFs is fine-tuned by twisting the branches • Rotation could play a key role in turn-on antenna effect Twisting and rotation of organic linkers co-exist in the solid state of metal-organic frameworks, one increasing luminescence and the other decreasing luminescence. Yin et al. find that steric hinderance and coordination of uranyl ions can control the twisting of branches of organic building blocks, offering good trade-off between twisting and rotation.