Induced-Fit-Identification in a Rigid Metal-Organic Framework for ppm-Level CO₂ Removal and Ultra-Pure CO Enrichment

Area of Science:

• Materials Science
• Chemical Engineering
• Environmental Science

Background:

• Physical adsorption is crucial for removing carbon dioxide (CO2) from crude syngas to produce eligible syngas.
• Key challenges include trapping low concentrations of CO2 and achieving high CO purity at elevated working temperatures.

Purpose of the Study:

• To develop a thermoresponsive metal-organic framework (MOF) for efficient CO2 capture and CO purification from syngas.
• To investigate the mechanism behind the MOF's performance at higher temperatures.

Main Methods:

• Synthesis and characterization of the thermoresponsive MOF, 1a-apz, from Mg2(dobdc) (1a) and aminopyrazine (apz).
• Variable-temperature adsorption tests, in situ high-resolution synchrotron X-ray diffraction (HR-SXRD), and computational simulations.
• Breakthrough tests using CO2/CO mixtures and complex quinary syngas mixtures.

Main Results:

• 1a-apz exhibits ultra-high CO2 capacity (145.0/197.6 cm3 g-1 at 0.01/0.1 bar, 298 K).
• Achieves ultra-pure CO (≥99.99%) at practical ambient temperatures.
• Demonstrates effective CO2 removal from 1/99 CO2/CO mixtures at 348 K, yielding 70.5 L kg-1 of high-purity CO.
• Successfully separates a quinary syngas mixture (H2/N2/CH4/CO/CO2).

Conclusions:

• The MOF's performance is attributed to induced-fit-identification, involving self-adaption of apz, multiple binding sites, and complementary electrostatic potential.
• 1a-apz presents a promising solution for high-temperature syngas purification, addressing critical industrial challenges.
• The material's thermoresponsive nature and tailored binding sites enable efficient separation of CO2 from CO.