Moisture-resistant Al-based MOF with helical SBUs for efficient CO2 adsorption, separation and desorption

Exploring CO 2 adsorption under humid conditions is crucial for practical applications. Herein, ZJU-521(Al) was synthesized using low-toxicity helical secondary building units (SBUs, [Al 5 (OH) 7 (−COO) 8 ] ∞ ) and tetrakis (4-carboxyphenyl)methane (H 4 MTTB) ligand, with excellent chemical stability. Saturated CO 2 adsorption capacities of ZJU-521(Al) reach 6.19 mmol/g at 273 K and 4.52 mmol/g at 298 K, respectively, and moderate isosteric heat of 28.23 kJ/mol, enabling low-energy regeneration. Simulation results reveal two CO 2 adsorption sites on ZJU-521(Al): site I, located near the helical SBUs and interwoven with the helical SBUs, and site II, situated near the H 4 MTTB ligand. ZJU-521(Al) can effectively separate CO 2 from the CO 2 /N 2 mixture, as identified by the ideal adsorbed solution theory values of 28.81 at 273 K and 40.83 at 298 K for CO 2 /N 2 (15/85) mixture, respectively. Dynamic adsorption experiments reveal dynamic CO 2 adsorption of 0.59 mmol/g under dry conditions and 0.54 mmol/g at 80% relative humidity (RH) for ZJU-521(Al), highlighting its moisture-resistant behavior for CO 2 adsorption under humid conditions. Most adsorbed CO 2 is readily desorbed by argon purging at 14 min (dry) and 12 min (80% RH) at 298 K, respectively. Therefore, ZJU-521(Al) emerges as a promising candidate for efficient CO 2 adsorption, separation, and desorption even under humid conditions.