Mixed-linker solid solutions of functionalized pillared-layer MOFs - adjusting structural flexibility, gas sorption,...

Area of Science:

• Materials Science
• Chemistry
• Nanotechnology

Background:

• Flexible metal-organic frameworks (MOFs) exhibit dynamic structural changes in response to external stimuli like guest molecules or temperature variations.
• Tuning framework flexibility is crucial for developing advanced functional materials with tailored properties.
• Mixed-linker solid solutions offer a promising approach for systematic control over MOF flexibility.

Purpose of the Study:

• To investigate the potential and limitations of using mixed-linker solid solutions to tune the flexibility of pillared-layer MOFs.
• To systematically examine how varying the ratio of functionalized benzenedicarboxylate (fu-bdc) linkers influences the structural and responsive properties of Zn2(fu-bdc)2x(fu-bdc)(2-2x)dabco MOFs.
• To understand the impact of linker composition on guest-responsive behavior, thermal expansion, and phase transitions.

Main Methods:

• Synthesis of a series of Zn2(fu(1)-bdc)2x(fu(2)-bdc)(2-2x)dabco MOFs with systematically varied linker ratios (x = 1.00, 0.75, 0.50, 0.25, 0.00).
• Characterization of structural flexibility using X-ray diffraction (XRD) under various conditions.
• Evaluation of guest adsorption/desorption properties (e.g., CO2) using gas physisorption measurements.
• Assessment of temperature-dependent structural changes and phase behavior via calorimetric measurements.

Main Results:

• Demonstrated successful synthesis of mixed-linker MOFs with precise control over linker ratios.
• Observed significant modulation of framework contraction upon guest removal by adjusting the fu-bdc linker composition.
• Characterized distinct breathing behaviors upon CO2 adsorption/desorption, correlating with linker ratios.
• Identified tunable thermoresponsive phase transitions and altered thermal expansivity based on the mixed-linker strategy.

Conclusions:

• Mixed-linker solid solutions provide a powerful and versatile strategy for fine-tuning the flexibility and responsiveness of pillared-layer MOFs.
• The systematic variation of linker ratios allows for targeted design of MOF materials with specific properties, such as controlled framework contraction and guest-induced breathing.
• This approach opens new avenues for developing advanced MOFs for applications requiring precise structural control and stimulus-responsive behavior.