Structural Adaptability Driven by Nonuniform Ligand Torsion and Relocation Enables Microregulated Photothermal...

Area of Science:

• Materials Science
• Crystallography
• Nanotechnology

Background:

• Dynamic metal-organic frameworks (MOFs) are programmable crystalline materials responsive to external stimuli.
• Understanding the relationship between ligand flexibility and framework rigidity is crucial for designing advanced MOFs.

Purpose of the Study:

• To synthesize and characterize two isostructural cobalt-based MOFs, NBU-X4 and NBU-X5, to investigate the impact of ligand structure on framework dynamics and photothermal properties.
• To elucidate the structure-property correlations between ligand torsion, framework adaptability, and photothermal efficiency.

Main Methods:

• Synthesis of two cobalt-based MOFs, [Co2(L1)2(L2)]n (NBU-X4) and [Co2(L1)2(L3)]n (NBU-X5), using specific organic ligands.
• Single-crystal X-ray diffraction analysis to determine the structural characteristics and flexibility of the MOFs.
• Photothermal testing under laser irradiation to evaluate temperature response and stability.

Main Results:

• NBU-X4 exhibits structural adaptability via ligand torsion, enabling reversible single-crystal-to-single-crystal transformations with modulated photothermal response.
• NBU-X5, with suppressed torsional motion due to steric hindrance, forms a rigid framework with high photothermal efficiency (316 °C at 1.6 W cm-2).
• NBU-X4 demonstrates durable photothermal cycling (50 cycles) and consistent temperature differences, suitable for memory-type photothermal sensing.

Conclusions:

• Ligand torsion and framework adaptability are key factors influencing the photothermal efficiency of dynamic MOFs.
• The study provides a rational design strategy for developing MOF-based temperature-responsive materials with tailored properties.
• These findings highlight the potential of dynamic MOFs in applications requiring precise thermal control and sensing.