Silk: A promising natural blend of amino acids for efficient CO2 capture

In recent years, various nanoporous solid sorbents have drawn significant research interest as promising carbon capture materials. However, the issues of high synthesis cost, limited CO2 adsorption capacity, slow adsorption-desorption kinetics, high sorbent regeneration temperature, and poor operational stability remain challenges to overcome before their practical implementation. In contrast, natural silk-fibroin, a blend of various amino acids, could be a promising material to realize low-cost carbon capture technology due to its amine-like CO2 capture behavior, light weight, natural abundance, scalable processing, and biocompatibility. Here, we present mulberry silk-derived silk-nano-fibroin aerogel that exhibits a high specific surface area and a remarkably high CO2 adsorption capacity (~3.65+-0.18 mmol CO2/gm sorbent at 0.15 atm CO2 and 5 oC), making it competitive with state-of-the-art solid sorbents. The thermogravimetry analysis reveals that the thermal degradation temperature of silk-nano-fibroin aerogel is around 250 {\deg}C, significantly higher than conventional amines used for carbon capture. Furthermore, the silk-nano-fibroin-based sorbent demonstrates rapid adsorption-desorption kinetics, complete regeneration at a temperature as low as 60 {\deg}C, promising stability over multiple adsorption-desorption cycles, and maintains its adsorption capacity under humid conditions. Overall, this study highlights natural silk's promising carbon capture potential for further exploration.