Clathrating CO₂ in a Supramolecular Granatohedron Cage with Noncovalent CO₂-NH₃ Interactions and High CO₂ Capture Efficiency under Ambient Conditions

Organic amine (R-NH₂) reagents as dominant chemical sorbents for CO₂ capture in industrial processes suffer from high energy compensation for regeneration. Herein, we, for the first time, report the finding of Co(III) coordinating with NH₃ molecules regulating the interaction between NH₃ and CO₂ to electrostatic interactions instead of a chemical reaction and achieve CO₂ capture under near-ambient conditions. NH₃ coordinating with Co(III) significantly reduces its alkalinity and reactivity with CO₂ owing to its lone-pair electron donation during coordination. Under a simple protocol, CO₂ induces the crystallization of CO₂@[Co(NH₃)₆][HSO₄][SO₄] clathrate into a hydrogen-bonded granatohedron cage from a cobaltic hexammine sulfate aqueous solution under a CO₂ pressure of 56 and 142 kPa at 275 and 298 K, respectively, with a CO₂ uptake weight content of 11.7%. We reveal that CO₂ interacts with cobaltous hexammine via supramolecular interactions rather than chemical bonding. The clathrate spontaneously separates from the solution as single crystals and readily releases CO₂ under ambient conditions in water for cyclic utilization without further treatment. In such a rapid supramolecular capture process, molecular recognition ensures exclusive CO₂ selectivity, and soluble clathrate enables the spontaneous CO₂ release at a low energy penalty, exhibiting excellent practical potential in carbon capture.