Shape-Memory Effect Enabled by Ligand Substitution and CO₂ Affinity in a Flexible SIFSIX Coordination Network

Area of Science:

• Materials Science
• Chemistry
• Nanotechnology

Background:

• Flexible coordination networks can exhibit reversible phase switching.
• Ligand modification is a key strategy for tuning material properties.
• Previous work on SIFSIX-23-Cu demonstrated reversible switching.

Purpose of the Study:

• To investigate the impact of linker ligand substitution on the properties of flexible coordination networks.
• To explore the potential of modified coordination networks for gas adsorption and separation.
• To understand the mechanism behind the observed shape-memory effect.

Main Methods:

• Synthesis of a modified coordination network, SIFSIX-23-CuN.
• Gas adsorption/desorption studies (N2, CO2) at various temperatures.
• Analysis of phase transitions using isotherms.
• Computational studies including molecular simulations and DFT calculations.

Main Results:

• Ligand substitution induced a shape-memory effect in SIFSIX-23-CuN.
• The material formed a kinetically stable porous phase with high CO2 affinity.
• A novel shape-memory phase (α') demonstrated excellent CO2/N2 separation performance (selectivity up to 700).
• Strong binding energies (Qst = 45-51 kJ/mol) and reversible phase transitions were observed.

Conclusions:

• Single-atom linker modification can effectively engineer shape-memory effects in coordination networks.
• SIFSIX-23-CuN is a promising material for selective CO2 capture and separation.
• The observed phenomena provide insights into the structure-property relationships in flexible porous materials.