(553d) Olsalazine-Based Metal?Organic Frameworks As a Platform for Cooperative Direct Air Capture of Carbon Dioxide

Direct air capture (DAC) and sequestration are crucial technologies for CO₂ removal from the atmosphere. Unlike traditional point source capture, DAC utilizes renewable energy for CO₂ extraction from any location, showing promise in climate change mitigation. However, capturing diluted CO₂ from the air requires materials with a strong CO₂ affinity while maintaining ease of regeneration. This challenge led to the development of switch-like CO₂ adsorbents critical for efficient DAC and material renewal. Some diamine-functionalized metal–organic frameworks (MOFs) exhibit a step-shaped isotherm due to a unique cooperative CO₂ adsorption mechanism, enhancing their effectiveness in CO₂ capture and regeneration processes. Previous studies have shown that adsorption capacity and step pressure in MOFs are influenced by both appended amine structures and framework pore diameters. Diamine-functionalized Mg₂(olz) (olz^4– = (E)-5,5′-(diazene-1,2-diyl)bis(2-oxidobenzoate)) has excellent performance in post-combustion carbon capture, offering high working capacities, low regeneration energies, and superior CO₂ selectivities over water due to a unique cooperative CO₂ adsorption mechanism. Despite these advantages, their exploration of DAC has been limited. Here, we introduce a novel member, 2-ampd–Mg₂(olz), which reveals its cooperative CO₂ adsorption behavior with achieving full capacity under DAC conditions. Spectroscopic analyses confirm its CO₂ capture mechanism through ammonium carbamate chain formation within the pores of the framework. Breakthrough and cycling experiments demonstrate its high capacity and stability in simulated DAC scenarios, even under high oxygen concentrations. These findings position 2-ampd–Mg₂(olz) as a highly promising material for durable and efficient CO₂ adsorption in DAC technology.