Energy-Efficient Iodine Uptake by a Molecular Host⋅Guest Crystal

Area of Science:

• Materials Science
• Supramolecular Chemistry
• Crystallography

Background:

• Porous organic crystals (POCs) based on macrocycles demonstrate significant sorption and separation capabilities.
• The influence of pre-adsorbed guests within macrocycles on adsorption properties remains largely unexplored.

Purpose of the Study:

• To investigate the impact of including trimethoxybenzyl-azaphosphatrane within cucurbit[8]uril (CB[8]) macrocycles on crystal properties.
• To explore the adsorption and optical characteristics of these novel molecular porous host·guest crystals (PHGC-1).

Main Methods:

• Synthesis of molecular porous host·guest crystals (PHGC-1) by incorporating trimethoxybenzyl-azaphosphatrane into CB[8].
• Characterization of adsorption properties, including spontaneous and selective iodine uptake under ambient conditions.
• Utilizing 1H NMR and DOSY to monitor guest exchange (H2O/I2).
• Assessment of second harmonic generation (SHG) properties of iodine-doped crystals.

Main Results:

• PHGC-1 crystals exhibit spontaneous and selective iodine adsorption at room temperature and atmospheric pressure without prior activation.
• The synthesis and operation of PHGC-1 avoid heat, moisture sensitivity, and energy-intensive activation steps, reducing energy costs.
• Iodine doping significantly alters the non-linear optical properties (SHG) of the non-centrosymmetric PHGC-1 crystals.

Conclusions:

• The inclusion of guests in macrocycles can lead to porous materials with unique adsorption behaviors.
• PHGC-1 represents a new class of porous materials with potential for energy-efficient applications in sorption and separation.
• Iodine doping offers a method to tune the non-linear optical properties of porous organic crystals.