Wet Chemical Etching Modulates Bulk and Surface Reactivity in Zeolitic Imidazolate Framework-8 for Selective CO ₂ Capture

Mitigating rising atmospheric CO 2 levels remains one of the most pressing global challenges. Among emerging solutions, solid adsorbent technologies offer efficient, reusable, and economically viable routes for CO 2 capture. Here, we contribute to this field by introducing a crystal-engineering strategy for zeolitic imidazolate framework-8 (ZIF-8), a robust and scalable metal–organic framework (MOF) synthesized under green, room-temperature conditions. Controlled wet chemical etching generates surface and bulk defects and exposes new crystal faces, increasing the number of coordinatively unsaturated Zn sites available for spermine grafting. This dual modification leads to an 84-fold enhancement in CO 2 uptake at 40 mbar compared to pristine ZIF-8. Breakthrough experiments (4 vol % CO 2 balanced with N 2 ) under both dry and humid conditions confirm selective and stable CO 2 capture, retaining ∼90% of uptake even at 75% relative humidity. In situ 13 CO 2 solid-state NMR provides direct molecular-level evidence of carbamate formation, confirming chemisorption interactions. Our findings demonstrate that wet chemical etching coupled with amine grafting is an attractive strategy for modulating bulk and surface reactivity in MOFs, unlocking previously inaccessible Zn sites and enabling high-performance, humidity-tolerant CO 2 capture under industrially relevant conditions.