Exclusive Recognition of CO₂ from Hydrocarbons by Aluminum Formate with Hydrogen-Confined Pore Cavities

Exclusive capture of carbon dioxide (CO2)from hydrocarbonsvia adsorptive separation is an important technology in the petrochemicalindustry, especially for acetylene (C2H2) production.However, the physicochemical similarities between CO2 andC(2)H(2) hamper the development of CO2-preferential sorbents, and CO2 is mainly discerned viaC recognition with low efficiency. Here, we report that the ultramicroporousmaterial Al-(HCOO)(3), ALF, can exclusively capture CO2 from hydrocarbon mixtures, including those containing C2H2 and CH4. ALF shows a remarkable CO2 capacity of 86.2 cm(3) g(-1) andrecord-high CO2/C2H2 and CO2/CH4 uptake ratios. The inverse CO2/C2H2 separation and exclusive CO2 capture performancefrom hydrocarbons are validated via adsorption isotherms and dynamicbreakthrough experiments. Notably, the hydrogen-confined pore cavitieswith appropriate dimensional size provide an ideal pore chemistryto specifically match CO2 via a hydrogen bonding mechanism,with all hydrocarbons rejected. This molecular recognition mechanismis unveiled by in situ Fourier-transform infrared spectroscopy, X-raydiffraction studies, and molecular simulations.