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

Abstract

Exclusive capture of carbon dioxide (CO2) from hydrocarbons via adsorptive separation is an important technology in the petrochemical industry, especially for acetylene (C2H2) production. However, the physicochemical similarities between CO2and C2H2hamper the development of CO2-preferential sorbents, and CO2is mainly discerned via C recognition with low efficiency. Here, we report that the ultramicroporous material Al(HCOO)3, ALF, can exclusively capture CO2from hydrocarbon mixtures, including those containing C2H2and CH4. ALF shows a remarkable CO2capacity of 86.2 cm3g-1and record-high CO2/C2H2and CO2/CH4uptake ratios. The inverse CO2/C2H2separation and exclusive CO2capture performance from hydrocarbons are validated via adsorption isotherms and dynamic breakthrough experiments. Notably, the hydrogen-confined pore cavities with appropriate dimensional size provide an ideal pore chemistry to specifically match CO2via a hydrogen bonding mechanism, with all hydrocarbons rejected. This molecular recognition mechanism is unveiled by in situ Fourier-transform infrared spectroscopy, X-ray diffraction studies, and molecular simulations.