Framework-Topology-Controlled Singlet Fission in Metal-Organic Frameworks

Area of Science:

• Materials Science
• Photochemistry
• Organic Electronics

Background:

• Singlet fission (SF) boosts photovoltaic efficiency by generating multiple excitons from one photon.
• Achieving efficient SF requires precise control over interchromophore coupling, which is challenging in traditional organic solids.
• Excimers and decoherence are critical factors influencing SF efficiency and triplet state isolation.

Purpose of the Study:

• To explore metal-organic frameworks (MOFs) as a platform for modular singlet fission (SF) processes.
• To investigate how MOF topology and conformational flexibility influence SF mechanisms.
• To demonstrate the tunability of dielectric environments within MOFs for optimizing SF.

Main Methods:

• Synthesis of three new MOFs using 9,10-bis(ethynylenephenyl)anthracene-derived struts.
• Characterization using steady-state and transient spectroscopy.
• Analysis of topology-defined packing density and anthracene core flexibility.

Main Results:

• MOFs enable modular SF by controlling chromophore assembly and conformational flexibility.
• The SF-active chromophores within MOFs can undergo either excimer-mediated or direct SF via a virtual charge-transfer (CT) state.
• Solution-stable MOFs provide a tunable dielectric environment that stabilizes the CT state, facilitating SF.

Conclusions:

• MOFs offer a versatile platform for controlling SF mechanisms and efficiency.
• Tuning the dielectric environment within MOFs is key to optimizing SF processes.
• This approach expands the utility of MOFs in photon energy conversion by generating long-lived triplet states.