Sequential Pore Functionalization in MOFs for Enhanced Carbon Dioxide Capture

The capture of carbon dioxide (CO2) is crucial for reducing greenhouse emissions and achieving net-zero emission goals. Metal–organic frameworks (MOFs) present a promising solution for carbon capture due to their structural adaptability, tunability, porosity, and pore modification. In this research, we explored the use of a copper (Cu­(II))-based MOF called m CBMOF-1. After activation, m CBMOF-1 generates one-dimensional channels with square cross sections, featuring sets of four Cu­(II) open metal sites spaced by 6.042 Å, allowing strong interactions with coordinating molecules. To investigate this capability, m CBMOF-1 was exposed to ammonia (NH3) gas, resulting in hysteretic NH3 isotherms indicative of strong interactions between Cu­(II) and NH3. At 150 mbar and 298 K, the NH3-loaded (∼1 mmol/g) material exhibited a 106% increase in CO2 uptake compared to that of the pristine m CBMOF-1. Carbon-13 solid-state nuclear magnetic resonance spectra and density functional theory calculations confirmed that the sequential loading of NH3 followed by CO2 adsorption generated a copper–carbamic acid complex within the pores of m CBMOF-1. Our study highlights the effectiveness of sequential pore functionalization in MOFs as an attractive strategy for enhancing the interactions of MOFs with small molecules such as CO2.