l-Leucine-Based Layered Coordination Polymer Supports for Immobilizing Basic Salts to Yield Solid CO₂ Adsorbents...

We demonstrate that amino acid-based coordination polymers can serve as supports for a variety of basic salts. A layered framework, bis(l-leucinato)zinc(II), Zn(Leu)₂, prepared by an aqueous, base-mediated procedure, provides crystallographically defined, carboxylato-bridged two-dimensional layered structures with intersheet surfaces. The interlayer spacing is molecularly tunable, and immobilizing potassium l-leucinate increases the interlayer spacing in two discrete steps. Using this host, diverse basic salts can be immobilized to give solid sorbents that remain macroscopic solids under humid, DAC-relevant conditions (400 ppm CO₂, 293 K dew point, 313 K) while delivering equilibrium CO₂ uptakes of 0.17-1.04 mmol g^-1. After accelerated oxidative aging in simulated air (400 ppm CO₂, 21% O₂, 293 K dew point) at 393 K for 24 h, the amino acid-based sorbent shows high retention in CO₂ capacity, whereas a conventional polyamine-based sorbent exhibits a marked decrease in the capacity. The combination of environmental durability and DAC-relevant performance establishes Zn(Leu)₂ as a general and modular platform for sustainable CO₂ capture technologies.