Enhancing CO₂ Adsorption in MIL-53(Al) through Pressure–Temperature Modulation: Insights from Guest–Host Interactions

Abstract

Metal–organic frameworks (MOFs) have garnered significant attention for their exceptional CO2 adsorption capabilities. Among them, MIL-53(Al) is uniquely known for its “breathing effect”, a reversible phase transition between large-pore and narrow-pore phases. While previous studies have explored the structural changes in MIL-53(Al) under varying conditions, this work represents an innovative investigation into the simultaneous effects of high pressure and high temperature on the CO2 adsorption performance of MIL-53(Al). Utilizing a diamond anvil cell as the high-pressure device, we employed in situ Fourier transform infrared spectroscopy to examine the structural changes in activated MIL-53(Al) under compression and its CO2 adsorption performance under specific simultaneous high-pressure and high-temperature conditions. Our findings reveal that heating serves as an effective strategy to augment CO2 adsorption by enhancing the mobility of the CO2 molecules under high pressure. Remarkably, the CO2 adsorption capacity of MIL-53(Al) surged when subjected to pressures from 0.20 to 1.24 GPa and temperatures up to the melting point of CO2. Detailed spectral analysis further elucidated the chemisorptive nature of host–guest interactions between the framework and CO2. These findings significantly advance our understanding of MOFs’ potential for carbon capture across a broad pressure–temperature spectrum.