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This study was to develop a low-cost N-doped porous biocarbon adsorbent that can directly adsorb CO2 in high-temperature flue gas from fossil fuel combustion. The porous biocarbon was prepared by nitrogen doping and nitrogen–oxygen codoping through K2CO3 activation. Results showed that these samples exhibited a high specific surface area of 1209–2307 m2/g with a pore volume of 0.492–0.868 cm3/g and a nitrogen content of 0.41–3.3 wt %. The optimized sample CNNK-1 exhibited a high adsorption capacity of 1.30 and 0.27 mmol/g in the simulated flue gas (14.4 vol % CO2 + 85.6 vol % N2) and a high CO2/N2 selectivity of 80 and 20 at 25 and 100 °C and 1 bar, respectively. Studies revealed that too many microporous pores could hinder CO2 diffusion and adsorption due to the decrease of CO2 partial pressure and thermodynamic driving force in the simulated flue gas. The CO2 adsorption of the samples was mainly chemical adsorption at 100 °C, which depended on the surface nitrogen functional groups. Nitrogen functional groups (pyridinic-N and primary and secondary amines) reacted chemically with CO2 to produce graphitic-N, pyrrolic-like structures, and carboxyl functional groups (−N–COOH). Nitrogen and oxygen codoping increased the amount of nitrogen doping content in the sample, but acidic oxygen functional groups (carboxyl groups, lactones, and phenols) were introduced, which weakened the acid–base interactions between the sample and CO2 molecules. It was demonstrated that SO2 and water vapor had inhibition effects on CO2 adsorption, while NO nearly has no effect on the complex flue gas. Cyclic regenerative adsorption showed that CNNK-1 possessed excellent regeneration and stabilization ability in complex flue gases, indicating that corncob-derived biocarbon had excellent CO2 adsorption in high-temperature flue gas.

Recently, researchers found the abilities of cepharanthine (CEP) to prevent and treat coronavirus. However, the study about CEP solid forms has been rarely reported. In this study, the crystal structure of CEP form I was first solved, and eight solvates were screened and discovered based on the conductor-like screening model for real solvents. The crystal structures of five solvates of CEP with methanol (SMeOH), acetonitrile (SACN), methyl acetate (SMA), ethyl acetate (SEA), and butyl acetate (SBA) were solved. The results showed that five solvates belonged to isolated-site solvates. Hydrogen bonding between the solvent molecule and the active pharmaceutical ingredient molecule was present only in SMeOH. The remaining four solvates formed C–H···O weak hydrogen bonds and C–H···π interactions between the host and guest. The mechanism of solvate formation was explained by calculating the packing coefficients, and it was proved that the introduction of solvent molecules mainly made the crystal structure packed more effectively. In addition, the desolvation of the five solvates were studied and found that the desolvation of SMeOH followed a cooperative mechanism, while SACN, SMA, SEA, and SBA conformed to a destruction-collapse mechanism.