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The cost of CO2 separation and energy consumption can be decreased through the use of CO2 adsorption. Due to the electron-rich heteroatoms in its network, polyimide (PI) has a remarkable affinity for CO2. Polyethylene glycol (PEG) can increase the layer spacing of polymers, so as to change the mass transfer of CO2 in it. Furthermore, the ether bond (-O-) in PEG has good affinity for CO2. In this study, PEG-1000 was introduced into PI aerogel by mild sol-gel method at low temperature, and freeze-drying was used to produce PI/PEG composite aerogels with directional pore structure. The effect of PEG-1000 content and directional pore structure of the PI/PEG composite aerogels on CO2 adsorption performance were further studied. The L-PI/PEG-4 composite aerogel, which contains 4 g PEG and is directionally frozen in liquid nitrogen, has a CO2 adsorption capacity of 16.76 cm3/g at 25°C and 1 bar. L-PI/PEG-4 aerogel also exhibits high CO2/N2 selectivity and adsorption cycle stability. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Developing highly efficient and stable photocatalysts is an effective method to achieve CO2 photocatalytic reduction. Herein, PI/WO3 aerogel photocatalyst was prepared by chemical amide reaction coupled with an ethanol supercritical drying technique. The novel aerogel photocatalysts exhibit excellent photocatalytic performance for reducing CO2 into CO. In particular, PI/WO3-10 aerogel photocatalyst shows the highest yield of CO (5.72 μmol g–1 h–1), which is ca 11-fold higher than that of the pristine PI aerogel. The high CO2 reduction activity can be attributed to the Z-scheme structure, which enhances the separation of photo-generated electron – holes, and induces H2O oxidation on WO3 nanosheets and CO2 reduction on PI aerogel. The photocatalytic reaction mechanism of CO2 when using PI/WO3 aerogel photocatalyst is proposed. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Polyacetylacetonatozirconium (PAZ) was used as precursor to synthesize ZrO 2 aerogel. • PAZ-ZrO 2 aerogel performed a compressive strength of 0.23 MPa and 20 ~ 25% strain. • The SSA (PV) of PAZ-ZrO 2 aerogel was 236 m2/g (1.568 cm3/g) after 1000 °C heat-treatment. Abstract Polyacetylacetonatozirconium was used as the precursor to synthesize ZrO 2 aerogel (PAZ-ZrO 2). The physical properties of the aerogel were compared with those generated from zirconyl chloride (ZOC-ZrO 2) and zirconyl nitrate (ZON-ZrO 2). PAZ-ZrO 2 aerogel has higher compressive strength (0.12–0.23 MPa) with lower density (0.12 ± 0.005 g/cm3) as compared to ZOC-ZrO 2 and ZON-ZrO 2 aerogel, of which the mechanical strengths are in the range of 0.02–0.15 MPa and the density of 0.13–0.17 g/cm3. After being treated at 1000 °C, the surface area (pore volume) of ZOC-ZrO 2 , ZON-ZrO 2 and PAZ-ZrO 2 aerogel are 210 m2/g (1.299 cm3/g), 223 m2/g (0.444 cm3/g) and 236 m2/g (1.568 cm3/g) respectively. [ABSTRACT FROM AUTHOR]

• Crack-free monolithic Al 2 O 3 Y 2 O 3 SiO 2 ternary aerogel was successfully synthesized by synchronous sol-gel method. • Al 2 O 3 Y 2 O 3 SiO 2 aerogel exhibited low density of 0.071 g/cm3 and high specific area up to 675.7 m²/g. • Mullite fiber reinforced Al 2 O 3 Y 2 O 3 SiO 2 aerogel showed excellent thermal insulation performance, the thermal conductivity at 1000 °C is only 0.079 W·m−1·K−1. Against the background of global energy shortages and the need for long-term flight safety of aerospace vehicles, traditional silica aerogels have the problems of insufficient temperature resistance and poor thermal insulation at high-temperatures, and are no longer able to meet the demand. In this study, a series of monolithic Al 2 O 3 Y 2 O 3 SiO 2 ternary aerogels were successfully synthesized via synchronous sol–gel and ethanol supercritical drying. Both the prepared aerogels and the calcined samples at 1000 °C exhibited a complete three-dimensional network structure and a high specific surface area (up to 675.7 m2/g and 214.4 m2/g), which was attributed to the supporting effect of the Al 2 O 3 component on the overall skeleton and the inhibiting effect of the Y 2 O 3 component on the crystal transformation. Mullite fiber reinforced Al 2 O 3 Y 2 O 3 SiO 2 aerogel composites were synthesized by vacuum impregnation using mullite fiber felt as a matrix. The prepared sample exhibit very low thermal conductivity (as low as 0.079 W⋅m−1·K−1 at 1000 °C). In summary, the good structural stability and high temperature thermal insulation performance make Al 2 O 3 Y 2 O 3 SiO 2 ternary aerogel have the potential of efficient service in more application scenarios. This study provides a product optimization reference idea for the thermal insulation material industry. [ABSTRACT FROM AUTHOR]

Biomass aerogel is attractive in various applications due to their renewable, biodegradable and eco-friendly advantages. Herein, a novel beta molecular sieve/carboxymethyl cellulose/polyvinyl alcohol composite aerogel (beta/CP) is prepared by direct mixing and directional freeze-drying as an efficient gas adsorbent with hierarchical porosity. The beta molecular sieve is uniformly dispersed in the three-dimensional skeleton of the aerogel. By adjusting the loading mass of the beta molecular sieve to constitute a reasonable porosity and pore size distribution, the synergistic effect between pore structures of different scales improves the adsorption performance. The experiment results of beta/CP-4 show that the CH 4 adsorption capacity can reach 60.33 cm3/g at 298 K and 100 bar, which is almost the same as that of the pure beta molecular sieve (62.09 cm3/g). The strong interaction between the aerogel and it prevents the molecular sieve agglomeration, improves the pore utilization, and also reduces the cost of using molecular sieve adsorbent. The above results indicate that the composite has good potential for application in the field of CH 4 storage. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • SAM aerogel is prepared by directional freeze-drying method. • Tuning carbonization temperature and activator ratio to optimize performance. • SAM-700-4 shows 3D interconnected structure with large specific surface area. • SAM-700-4 shows excellent specific capacitance of 441.80 F/g at 0.5 A/g. • SAM-700-4//SAM-700-4 all-solid-state supercapacitor exhibit high energy density. Hierarchical porous carbon shows great potential in the field of energy storage due to high porosity, large surface area, and excellent electrical conductivity. Here, we successfully fabricated carbon aerogel derived from sodium alginate/melamine composite (SAM) by directional freeze-drying combined with simple carbonization and activation process. The optimal SAM-700-4 possesses a high nitrogen (5.67 at.%) and oxygen (8.98 at.%) contents along with high specific surface area of 2577.62 m2/g and unique directional channel structure. Due to their synergistic effect, the SAM-700-4 electrode exhibits a high specific capacitance of 441.80 F/g at a current density of 0.5 A/g. Interestingly, the all-solid-state symmetric supercapacitor based on SAM-700-4//SAM-700-4 in PVA/SA/KOH gel electrolyte has a large energy density of 20.87 Wh/kg at a power density of 4000 W/kg and exhibits excellent cycling stability. It is believed that this N, O co-doped directional hierarchical porous carbon aerogel may show promising prospects as advanced energy storage materials. [ABSTRACT FROM AUTHOR]

The rare earth lanthanum aerogel monolith with low chlorine ions were synthesized by a modified epoxide gelation method. The actual wt% of Cl could be reduced to as low as 0.371 wt%. • Rare earth lanthanum based (La-) aerogels were prepared by a modified epoxide gelation method. • The La-aerogels monoliths have low chlorine (0.371 wt%) and high specific surface area (74 m2/g). • The La-aerogels were well crystallized and the microstructures consisted of La(OH) 3 rods and La 2 O 2 CO 3 lamellae. Rare earth lanthanum based aerogels with reduced chlorine ions were produced by a modified sol–gel process. In the process, the La3+ precursor was designed to coordinate acetylacetone to form a La-complex. Ethanediamine was added in sol solution to form hydrochloride precipitates that were filtered in the following step. After supercritical drying, La-aerogel monoliths with lamella and rod microstructure were achieved. The Ion Chromatography showed that the chlorine within the aerogel synthesized by an optimized recipe reduced to as low as 0.371 wt%, in compared to the well-established method (3.909 wt%). The sol–gel mechanism was explored in detail. [ABSTRACT FROM AUTHOR]

• ZIF-8 derived porous carbon is supported on carbon aerogels derived from chitosan. • The composite possesses hierarchical porous structure with moderate N contents. • The composite has an ultrahigh specific surface area of 3075.5 m2/g. • The composite yields a large specific capacitance and outstanding cycling stability. In this study, chitosan was used to prepare nitrogen-doped carbon aerogels (CAs) anchored by ZIF-8 derived porous carbon (ZIF-8-C) using a facile in-situ deposition method combined with subsequent carbonization. CAs possessing a 3D mesoporous structure with interlaced nanosheets can be used as the skeleton for growth of ZIF-8 derived microporous carbon. The coexistence of mesopores and micropores can not only create more channels for electrolyte ions accessing, but also can provide electrical-double-layer capacitance. The results of electrochemical performance revealed that the ZCCA composite electrode shows the large specific capacitance of 241.6 F/g at a current density of 0.5 A/g in 2.0 M KOH electrolyte and superior cycle performance (capacity retention of 90% after 5000 cycles). The improvement in the electrochemical properties is owed to its hierarchically porous structure, ultrahigh specific surface area and moderate nitrogen contents. The preparation method offers the smart design of CAs-supported MOF-derived material for high-performance energy storage applications. [ABSTRACT FROM AUTHOR]