Purification of Waste-Generated Biogas Mixtures Using Covalent Organic Framework's High CO 2 Selectivity.

Development of crystalline porous materials for selective CO ₂ adsorption and storage is in high demand to boost the carbon capture and storage (CCS) technology. In this regard, we have developed a β-keto enamine-based covalent organic framework ( VM-COF ) via the Schiff base polycondensation technique. The as-synthesized VM-COF exhibited excellent thermal and chemical stability along with a very high surface area (1258 m ² g ^-1 ) and a high CO ₂ adsorption capacity (3.58 mmol g ^-1 ) at room temperature (298 K). The CO ₂ /CH ₄ and CO ₂ /H ₂ selectivities by the IAST method were calculated to be 10.9 and 881.7, respectively, which were further experimentally supported by breakthrough analysis. Moreover, theoretical investigations revealed that the carbonyl-rich sites in a polymeric backbone have higher CO ₂ binding affinity along with very high binding energy (-39.44 KJ mol ^-1 ) compared to other aromatic carbon-rich sites. Intrigued by the best CO ₂ adsorption capacity and high CO ₂ selectivity, we have utilized the VM-COF for biogas purification produced by the biofermentation of municipal waste. Compared with the commercially available activated carbon, VM-COF exhibited much better purification ability. This opens up a new opportunity for the creation of functionalized nanoporous materials for the large-scale purification of waste-generated biogases to address the challenges associated with energy and the environment.