Switching molecular recognition selectivities by temperature in a diffusion-regulatory porous material

Area of Science:

• Materials Chemistry
• Supramolecular Chemistry
• Chemical Engineering

Background:

• Nature utilizes switchable recognition systems, like biological membranes, which adapt selectivity with stimuli.
• Artificial host-guest systems struggle with switchable recognition due to fixed affinity orders.
• Developing stimuli-responsive artificial systems for selective guest binding remains a challenge.

Purpose of the Study:

• To develop an artificial host-guest system with temperature-switchable recognition for similar gaseous guests.
• To achieve selective separation of carbon dioxide (CO2) and acetylene (C2H2) by manipulating external stimuli.
• To investigate a diffusion-regulatory mechanism in a dynamic porous crystal for guest selectivity control.

Main Methods:

• Design and synthesis of a dynamic porous crystal with ultrasmall pores and a mobile organic moiety.
• Utilizing a diffusion-regulatory mechanism driven by temperature changes.
• Employing temperature as an external stimulus to switch guest recognition selectivity.

Main Results:

• The dynamic porous crystal demonstrated temperature-responsive recognition of CO2 and C2H2.
• Selective adsorption of CO2 at low temperatures and C2H2 at high temperatures was achieved.
• High separation factors were obtained: 498 for CO2/C2H2 and 181 for C2H2/CO2.

Conclusions:

• A novel dynamic porous crystal enables switchable recognition of CO2 and C2H2 based on temperature.
• The flip-flop motion of the organic moiety within the crystal pores regulates gas diffusion and selectivity.
• This approach offers a promising strategy for selective gas separation using stimuli-responsive materials.