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

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.