Calcium-Based Metal-Organic Framework for Simultaneous Capture of Trace Propyne and Propadiene from Propylene

Area of Science:

• Materials Science
• Chemical Engineering
• Separation Science

Background:

• Separating trace propyne and propadiene from propylene is crucial but challenging due to similar properties and low concentrations.
• Existing industrial processes are energy-intensive, necessitating more efficient purification methods.

Purpose of the Study:

• To develop a highly stable and cost-effective metal-organic framework (MOF) for the selective capture of propyne and propadiene.
• To investigate the adsorption mechanism and performance of the MOF in multicomponent mixtures.

Main Methods:

• Synthesis of a Ca-based MOF using inexpensive calcium carbonate and squaric acid.
• Adsorption experiments to determine uptake capacities for propyne and propadiene at low pressures.
• Multicomponent breakthrough experiments to evaluate simultaneous removal from propylene.
• Density Functional Theory (DFT) simulations and in situ single-crystal X-ray diffraction to elucidate binding interactions.

Main Results:

• The Ca-based MOF achieved record high uptake capacities: 2.44 mmol/g for propyne and 2.64 mmol/g for propadiene at 5 mbar.
• Demonstrated excellent performance in simultaneous removal of both impurities from propylene in breakthrough tests.
• Identified cooperative binding mechanisms, including π-π stacking and C-H···O interactions, responsible for strong adsorption.

Conclusions:

• The developed calcium squarate MOF establishes a new benchmark for adsorptive purification of propylene.
• The material shows significant potential for practical industrial applications due to its high efficiency and stability.
• The findings pave the way for energy-efficient separation of similar hydrocarbons.