The release of the model drug theophylline from silica-pectin aerogels was investigated. The composite aerogels were prepared via impregnation of pectin alcogels with silica sol, followed by in situ silica gelation and drying with supercritical CO2. The structural and physico-chemical properties of the aerogels were tuned via the preparation conditions (type of silica sol, calcium crosslinking of pectin or not). Theophylline was loaded via impregnation and its release into simulated gastric fluid was studied during 1 h followed by release into simulated intestinal fluid. The swelling, mass loss and theophylline release behavior of the composites were analyzed and correlated with material properties. It followed that only aerogels prepared with calcium-crosslinked pectin and polyethoxydisiloxane were stable in aqueous systems, exhibiting a slow theophylline release governed by near-Fickian diffusion.

A phosphorus-doped carbon nanotube (CNT) aerogel as the support material was loaded with Pt nanoparticles in fuel cell-type gas sensors for ultrasensitive H2 detection. The high surface area of the CNT scaffold is favorable to providing abundant active sites, and the high electrical conductivity facilitates the transport of carriers generated by electrochemical reactions. In addition, the CNT aerogel was doped with phosphorus (P) to further enhance the conductivity and electrochemical catalytic activity. As a result, the fuel cell-type gas sensor using the Pt/CNT aerogel doped with the optimal P content as the sensing material shows considerable performance for H2 detection at room temperature. The sensor exhibits an ultrahigh response of -921.9 μA to 15,000 ppm of H2. The sensitivity is -0.063 μA/ppm, which is 21 times higher than that of the conventional Pt/CF counterpart. The sensor also exhibits excellent repeatability and humidity resistance, as well as fast response/recovery; the response/recovery times are 31 and 4 s to 3000 ppm of H2, respectively. The modulation of the structure and catalytic properties of the support material is responsible for the improvement of the sensor performance, thus providing a feasible solution for optimizing the performance of fuel cell-type gas sensors.

Tailoring the properties of cellulose aerogel beads was investigated in the present study by using weak organic acids as coagulants. Three different weak acids were specifically chosen, acetic acid, lactic acid and citric acid. For comparative studies, a strong acid, hydrochloric acid was examined. The production of aerogel beads by conventional dropping technique was controlled and optimized for weak acids. Aerogels were characterized by density analyses, scanning electron microscopy, nitrogen adsorption-desorption analysis, X-ray powder diffractometry and IR spectroscopy. In common, all the aerogel beads showed interconnected nanofibrillar network, high specific surface area, high pore volume, high porosity and meso- and macroporous structure. In particular, when the weakest acid (acetic acid) was used as coagulant in the regeneration bath, the lowest shrinkage was observed. As a result, the cellulose aerogel beads produced from acetic acid showed the highest values of specific surface area (423 m2·g-1) and pore volume (3.6 cm3·g-1). The porous structure can be tuned by the choice of regeneration bath having either strong acid or high concentration of weak acid. The aerogel beads were pure and showed cellulose II crystallinity. Hence this study paves an alternative path way to tailor the properties of cellulose aerogel beads.

Passive daytime radiative cooling (PDRC) technology offers a green and sustainable strategy for cooling, eliminating the need for external energy sources through its exceptional efficiency in heat radiation and sunlight reflection. Despite its benefits, the widespread usage of non-biodegradable PDRC materials has unfortunately caused environmental pollution and resource wastage. Furthermore, the effectiveness of outdoor PDRC materials can be significantly diminished by rainfall. In this work, a superhydrophobic composite aerogel composed of stereocomplex-type polylactide and ultra-fine glass fiber has been successfully developed through simple physical blending and freeze-drying, which exhibits low thermal conductivity (36.26 mW m-1 K-1) and superhydrophobicity (water contact angle up to 150°). Additionally, its high solar reflectance (91.68 %) and strong infrared emissivity (93.95 %) enable it to effectively lower surface temperatures during daytime, resulting in a cooling effect of approximately 3.8 °C below the ambient temperature during the midday heat of summer, with a cooling power of 68 W/m2. This aerogel offers an environmentally friendly and sustainable approach for the utilization of radiative refrigeration materials, paving the way for environmental protection and sustainable development.

Intelligent and diversified development of modern detection technology greatly affects the battlefield survivability of military targets, especially infrared, acoustic wave, and radar detection expose targets by capturing their unavoidable infrared radiation, acoustic wave, and electromagnetic wave information, greatly affecting their battlefield survival and penetration capabilities. Therefore, there is an urgent need to develop stealth-protective materials that can suppress infrared radiation, reduce acoustic characteristics, and weaken electromagnetic signals. Fibrous three-dimensional porous materials, with their high porosity, excellent structural adjustability, and superior mechanical properties, possess strong potential for development in the field of stealth protection. This article introduced and reviewed the characteristics and development process of fibrous three-dimensional porous materials at both the micrometer and nanometer scales. Then, the process and characteristics of preparing fibrous three-dimensional porous materials through vacuum forming, gel solidification, freeze-casting, and impregnation stacking methods were analyzed and discussed. Meanwhile, their current application status in infrared, acoustic wave, and radar stealth fields was summarized and their existing problems and development trends in these areas from the perspectives of preparation processes and applicability were analyzed. Finally, several prospects for the current challenges faced by fibrous three-dimensional porous materials were proposed as follows: functionally modifying fibers to enhance their applicability through self-cross-linking; establishing theoretical models for the transmission of thermal energy, acoustic waves, and electromagnetic waves within fibrous porous materials; constructing fibrous porous materials resistant to impact, shear, and fracture to meet the needs of practical applications; developing multifunctional stealth fibrous porous materials to confer full-spectrum broadband stealth capability; and exploring the relationship between material size and mechanical properties as a basis for preparing large-scale samples that meet the application\'s requirement. This review is very timely and aims to focus researchers\' attention on the importance and research progress of fibrous porous materials in the field of stealth protection, so as to solve the problems and challenges of fibrous porous materials in the field of stealth protection and to promote the further innovation of fibrous porous materials in terms of structure and function.

Aromatic polyisocyanurate (PIR) aerogels are recognized as advanced porous materials and extensively studied due to their lightweight nature, high porosity, and specific surface area, which attribute to their outstanding thermal insulation properties. The inherent thermal stability of the PIR moieties, combined with great insulating performance, renders PIR aerogels highly suitable for building insulation applications. Nevertheless, materials containing isocyanurate obtained through direct trimerization of aromatic isocyanates exhibit brittleness, resulting in inferior mechanical performance. In order to enhance the processability of the PIR aerogels, we propose a cocyclotrimerization approach involving mixtures of mono- and difunctional aromatic isocyanates. This approach is designed to develop a PIR network with decreased cross-linking density and brittleness. Herein, we developed an array of PIR aerogels from different alkyl chain-modified isocyanate mixtures. The resulting PIR aerogels exhibited high porosity (>89%), a large surface area (∼300 m2/g), superinsulating performance with ultralow thermal conductivity (∼16.8 mW m-1 K-1), notable thermal stability (Td5% ∼ 250 °C), improved mechanical performance, and intrinsic hydrophobicity without the need for postmodification. These high-performance organic aerogels hold significant promise for applications requiring superinsulating materials.

Dyes, as organic pollutants, are causing increasingly severe environmental problems. Metal-organic frameworks (MOFs) are considered promising dye adsorbents; however, their application is limited due to their powder or solid particle forms and limited reusability. Therefore, this study proposes an innovative approach to develop a novel MOF-based composite aerogel, specifically a HKUST-1/polyacrylonitrile nanofibers/regenerated cellulose (HKUST-1/PANNs/RC) composite aerogel adsorbent, for the adsorption of pollutants in water. This adsorbent was successfully prepared using a simple method combining covalent crosslinking, quick freezing, freeze-drying, in-situ growth synthesis, and solvothermal techniques. The HKUST-1/PANNs/RC composite aerogel exhibits a significantly large specific surface area, which is approximately 64 times greater than that of PANNs/RC (10.45 m2·g-1), with a specific surface area of 669.9 m2·g-1. The PANNs serve as a support framework, imparting excellent mechanical properties to the composite aerogel, enhancing its overall stability and recoverability. Additionally, the composite aerogel contains numerous -COOH and -OH groups on its surface, providing strong acid resistance and facilitating interactions with pollutant molecules through electrostatic interactions, π-π conjugation, n-π* interactions, and hydrogen bonding, thereby promoting the adsorption process. Using methylene blue (MB) as a probe molecule, the study results demonstrate that the HKUST-1/PANNs/RC composite aerogel has an adsorption capacity of 522.01 mg·g-1 for MB (25 h), exhibiting excellent adsorption performance. This composite aerogel shows great potential for application in water pollution control.

The assembly of two-dimensional (2D) nanomaterials into a three-dimensional (3D) aerogel can effectively prevent the problem of restacking. Here, nanofiber-reinforced MXene/reduced graphene oxide (rGO) conductive aerogel is prepared via the hydrothermal reduction of GO using pyrrole and in situ composite with MXene. Combined with low-content 2D conductive nanosheets (MXene and rGO) as \"brick\", conductive polypyrrole as \"mortar\", and one-dimensional (1D) nanofiber as \"rebar\", a strong interfacial cross-linking of MXene and rGO nanosheets is realized through covalent and noncovalent bonds to synergistically improve its mechanical performance. Based on the prepared MXene/rGO aerogel, a high-performance piezoresistive sensor with a sensitivity of up to 20.80 kPa-1 in a wide pressure range of 15.6 kPa is obtained, and it can withstand more than 5000 cyclic compressions. Besides, the sensor shows a stable output and can be applied to monitor various human motion signals. In addition, an all-solid-state supercapacitor electrode is also fabricated, which shows a high area-specific capacitance of up to 274 mF/cm2 at a current density of 1 mA/cm2.

The construction of supramolecular aerogels still faces great challenges. Herein, we present a novel bio-based supramolecular aerogel derived from G-Quadruplex self-assembly of guanosine (G), boric acid (B) and sodium alginate (SA) and the obtained GBS aerogels exhibit superior flame-retardant and thermal insulating properties. The entire process involves environmentally friendly aqueous solvents and freeze-drying. Benefiting from the supramolecular self-assembly and interpenetrating dual network structures, GBS aerogels exhibit unique structures and sufficient self-supporting capabilities. The resulting GBS aerogels exhibit overall low densities (36.5-52.4 mg/cm3), and high porosities (>95 %). Moreover, GBS aerogels also illustrate excellent flame retardant and thermal insulating properties. With an oxygen index of 47.0-51.1 %, it can easily achieve a V-0 rating and low heat, smoke release during combustion. This work demonstrates the preparation of intrinsic flame-retardant aerogels derived from supramolecular self-assembly and dual cross-linking strategies, and is expected to provide an idea for the realization and application of novel supramolecular aerogel materials.

A green approach based on simultaneous starch aerogel formation-curcumin impregnation via supercritical fluid technology was used to increase the bioavailability of curcumin. The loading amounts of curcumin were 16.4, 21.4, and 24.9 mg/g of aerogel for the 25% Amyl-loaded, 55% Amyl-loaded, and 72% Amyl-loaded samples, respectively. Curcumin-loaded aerogels showed the eventual distribution of curcumin in the hydrophobic area of the internal structure of the aerogels. In vitro gastrointestinal release profiles demonstrated the enhanced curcumin release from the curcumin-loaded aerogel formulations produced by the SC-CO2 technology over free curcumin. After intestinal digestion, the percentage of released curcumin from 25% Amyl-loaded, 55% Amyl-loaded, and 72% Amyl-loaded was 7.2, 12.1, and 12.1%, respectively, while the release of native curcumin was only 0.5%. Caco-2 cell permeation studies revealed superior bioavailability of curcumin from the curcumin-loaded aerogels. Curcumin-loaded aerogels exhibited improved storage stability than free curcumin.