Impacts of Fluorination at the Ortho‐Position of Carboxy Groups on Tetrakis(biphenyl)ethene‐Based Hydrogen‐Bonded Framework

Why It Matters

Fluorination offers a scalable strategy to customize HOF structures and their emission properties, opening pathways for advanced optoelectronic devices and smart materials. Understanding these molecular‑level effects accelerates material‑by‑design approaches in the rapidly growing organic electronics market.

Key Takeaways

• Ortho-fluorination twists CBPE arms, altering HOF topology.
• F-CBPE-1 forms non-interpenetrated sql sheets versus interpenetrated CBPE.
• Solvated F-CBPE HOF emits blue light in <15 ps via ICT.
• Desolvation red-shifts emission to excimer-like species in 120 ps.
• Fluorination enables tunable fluorescence for optoelectronic applications.

Pulse Analysis

Fluorination has become a cornerstone technique for fine‑tuning the assembly of crystalline organic materials, and this study adds a compelling example in the realm of hydrogen‑bonded organic frameworks (HOFs). By inserting fluorine atoms at the ortho positions of carboxy phenyl groups, the researchers forced the peripheral arms of the tetraphenylethene core to adopt a more twisted geometry. This subtle steric effect cascades into a dramatically different supramolecular architecture: the fluorinated F‑CBPE assembles into a single, staggered sql‑type sheet network (F‑CBPE‑1) that avoids the three‑directional interpenetration seen in the non‑fluorinated CBPE counterpart. Such topological control is valuable for designers seeking predictable pore environments and mechanical stability in porous organic solids.

Beyond structural manipulation, the fluorinated HOF exhibits striking photophysical behavior. In its solvated state, the framework displays a rapid blue emission driven by an intramolecular charge‑transfer (ICT) process occurring in less than 15 picoseconds. When the solvent is removed, the stacking arrangement shifts, fostering excimer‑like interactions that red‑shift the emission within 120 picoseconds. This dual‑mode fluorescence—fast ICT versus slower excimer formation—highlights how minute chemical modifications can toggle optical outputs, a feature highly prized in sensing, imaging, and light‑emitting applications.

The implications for industry are clear. Tunable fluorescence combined with controllable crystal topology positions fluorinated HOFs as promising candidates for next‑generation optoelectronic components, such as organic LEDs, photodetectors, and smart coatings. Their solution‑processable nature aligns with low‑cost manufacturing trends, while the ability to engineer emission wavelengths through simple fluorine placement reduces reliance on complex synthetic routes. As the market for flexible, lightweight organic electronics expands, insights from this work provide a practical blueprint for rapid material iteration and commercialization.