Ultrafast CO₂ Capture from Dilute Streams in Quasi-Equipotential Pores of Metal-Organic Frameworks

Solid sorbents capable of capturing CO₂ at particularly low concentrations with rapid kinetics are crucial for effective CO₂ capture. Here, we report ZnDTZ, a metal-organic framework (MOF) designed with an optimized pore size and functionalized pore surfaces tailored for CO₂ adsorption. ZnDTZ MOF exhibits exceptional CO₂ capture performance, achieving an uptake of 1.97 mmol/g at 303 K and 0.05 bar. The spatial distribution of CO₂ molecules and their interactions with the MOF are revealed by a combination of in situ Fourier transform infrared (FTIR) spectroscopy, density functional theory (DFT) calculations, and grand canonical Monte Carlo (GCMC) simulations which indicate that the molecules are stabilized within the pores through multiple binding sites, significantly enhancing adsorption efficiency at low concentrations. Remarkably, ZnDTZ shows unusually fast CO₂ adsorption kinetics compared to the current benchmark MOF adsorbent, CALF-20, despite similarities in chemical composition. A comprehensive analysis of adsorption kinetics and DFT calculations reveals that the enhanced performance arises from barrierless diffusion within the pores, enabled by the equipotential surface of ZnDTZ, achieved through the contiguous arrangement of the adsorption sites. Notably, ZnDTZ demonstrates excellent recyclability, maintaining stable performance over 200 adsorption-desorption cycles.