A novel combining strategy of cellulose aerogel and hierarchically porous metal organic frameworks (HP-MOFs) to improve the CO2 absorption performance

High CO2 concentration in atmosphere causes serious environmental issues, and carbon capture and storage technologies have attracted attention as a means to reduce the atmospheric CO2 concentration. Metal-organic frameworks (MOFs) can potentially be used for CO2 adsorption, but their poor stability and microporosity limit their applications. Herein, a novel strategy was proposed to combine a cellulose aerogel and hierarchically-porous MOFs (HP-MOFs) with larger pores. According to this strategy, a series of microcrystalline cellulose/HP-UIO-66-NH2 hybrid aerogels (MC-HUN-X) was constructed by adding a modulator (monocarboxylic acid, MA), followed by the in-situ growth of HP-UIO-66-NH2 on a cellulose aerogel. By adjusting the chain length of MA, the structure–function relationship between pore size and the CO2 adsorption capacity of MC-HUN-X was explored. The results showed that the CO2 adsorption capacity increased first and then decreased upon increasing the MOFs pore size, while the adsorption selectivity of CO2 continuously increased. Among all samples, MC-HUN-4 with a moderate pore size had the highest CO2 adsorption capacity (1.90 mmol/g at 298 K and 1 bar) and adsorption selectivity (13.02 and 2.40 for CO2/N2 and CO2/CH4). The combination with a cellulose aerogel endowed MC-HUN-X with excellent mechanical stability and reusability. Cellulose/HP-UIO-66-NH2 hybrid aerogel with larger aperture sizes of MOF showed excellent adsorption capacity and selectivity for CO2, and the combination with aerogel could effectively improve the mechanical stability and reusability.