Search

Hierarchically porous metal–organic frameworks (HP-MOFs) possess the advantages of the high porosity of MOFs and unique properties, such as a wide pore size range. Hierarchically porous ZIF-8 (HP-ZIF-8) was facilely fabricated via a one-step method in supercritical CO2 (scCO2) using a competitive ligand. The mesoporous structure and morphology of HP-ZIF-8 can be easily adjusted by changing the dosage of competing ligands and the reaction temperature. When the molar ratio of zinc acetylacetonate, 2-methylimidazole, and 2-butyl-1H-imidazole was 1 : 1 : 6, the HP-ZIF-8 with micropores (1.7 nm) and mesopores (3.9–30 nm) was synthesized at 50 °C and 30 MPa for 3 hours with excellent reproducibility. The as-synthesized ZIF-8 shows a high activity for CO2 adsorption, and the CO2 equilibrium adsorption capacity reached up to 1.49 mmol g−1 sorbent at 25 °C and 0.1 MPa. Moreover, the CO2 equilibrium adsorption capacity of HP-ZIF-8 was maintained at 1.36 mmol g−1 sorbent after 7 cycles. [ABSTRACT FROM AUTHOR]

The practical application of silica aerogels is an enormous challenge due to the difficulties in improving both mechanical property and thermal insulation performance. In this work, silk fibroin was used as scaffold to improve the mechanical property and thermal insulation performance of silica aerogels. The ungelled SiO2 precursor solution was impregnated into silk fibroin to prepare silk fibroin-SiO2 composite aerogels via sol-gel method followed by freeze-drying. By virtue of the interfacial hydrogen-bonding interactions and chemical reactions between silk fibroin and silica nanoparticles, SiO2 was well-dispersed in the silk fibroin aerogel and composite aerogels exhibited enhanced mechanical property. By increasing the loading of silk fibroin from 15 wt % to 21 wt %, the maximum compressive stress was enhanced from 0.266 to 0.508 MPa when the strain reached 50%. The thermal insulation performance of the composite aerogels was improved compared with pure silica aerogel, as evidenced that the thermal conductivity was decreased from 0.0668 to 0.0341 W·m−1·K−1. Moreover, the composite aerogels exhibited better hydrophobicity and fire retardancy compared to pure silica aerogel. Our work provides a novel approach to preparing silk fibroin-SiO2 composite aerogels with enhanced mechanical property and thermal insulation performance, which has potential application as thermal insulation material. [ABSTRACT FROM AUTHOR]