Purification of Waste-Generated Biogas Mixtures Using Covalent Organic Framework's High CO₂ Selectivity

Development of crystalline porous materials for selective CO₂ 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 m² g^-1) and a high CO₂ adsorption capacity (3.58 mmol g^-1) at room temperature (298 K). The CO₂/CH₄ and CO₂/H₂ 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 CO₂ binding affinity along with very high binding energy (-39.44 KJ mol^-1) compared to other aromatic carbon-rich sites. Intrigued by the best CO₂ adsorption capacity and high CO₂ 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.