An anion-functionalized MOF based on electrostatic potential matching strategy for efficient capture of CO2 from high temperature and humid flue gas

Abstract

Efficient capture of CO₂ from flue gas will bring significant environmental and economic benefits. But the process is full of challenge because high temperature and humid flue gas always damages the adsorbent. In the present work, a stable anion-pillared MOF (named HBU-24) was obtained by the assembly of ligand L (L = 1,1,2,2-tetra(pyridin-4-yl)ethene), Cd²⁺ and TiF₆²⁻ ions. The BET surface area of HBU-24 achieves 769.9 m²/g and two kind of pore sizes are found (5.2 Å and 8.6 Å). Due to the matching of the electrostatic potential of fluorine atoms of TiF₆²⁻ with that of carbon atoms of CO₂, the adsorption capacity of CO₂ is as high as 80.2 cm³/g at ambient condition, but the uptakes of CH₄ and N₂ are relatively low (16.0 cm³/g and 3.0 cm³/g). The IAST selectivity of CO₂/N₂ (v/v: 15/85) and CO₂/CH₄ (v/v: 50/50) was calculated as 1662.2 and 63.3. More importantly, it can also efficiently capture CO₂ even at 323 K (59.8 cm³/g). The adsorption mechanism was elucidated through GCMC and DFT calculations. Furthermore, dynamic breakthrough experiments were carried out under different temperature and humidity conditions, the penetration time of CO₂ was longer than that of N₂, which further proved that HBU-24 was suitable to capture CO₂ from high temperature and humid flue gas.