Bioinspired Reconfiguration of Alkylamines into Metal–Organic Frameworks for Robust Direct Air Capture

Exploration of molecularly engineered or polymer-based CO₂ adsorbents for direct air capture (DAC) has plateaued, with diminishing returns from functionalization strategies. Inspired by protein folding, we propose a new dimension for CO₂ sorbent discovery by structurally reconfiguring alkylamines into a polycyclic linker. The obtained dimeric butylamine linker is subsequently incorporated into a metal-organic framework, NUS-110, via a mechanochemical approach. NUS-110 exhibits a DAC capacity of 0.89 mmol/g under dry conditions (400 ppm CO₂) and 1.35 mmol/g under humid conditions (30% RH). Notably, NUS-110 shows strong water tolerance during DAC, attributable to its characteristic sigmoidal adsorption behavior. Furthermore, the dimeric butylamine moiety exhibits exceptional oxidative stability, maintaining stable performance across 20 DAC cycles due to its optimized steric configuration. Dynamic breakthrough experiments confirm the practical viability, with humid conditions improving the kinetics via water-assisted reaction pathways. This study introduces a paradigm shift in the development of DAC sorbents, featuring enhanced humidity tolerance and oxidative resilience to improve their suitability for practical deployment.