Ultralight and Robust Covalent Organic Framework Fiber Aerogels.

Shaping covalent organic frameworks (COFs) into macroscopic objects with robust mechanical properties and hierarchically porous structure is of great significance for practical applications but remains formidable and challenging. Herein, a general and scalable protocol is reported to prepare ultralight and robust pure COF fiber aerogels (FAGs), based on the epitaxial growth synergistic assembly (EGSA) strategy. Specifically, intertwined COF nanofibers (100-200 nm) are grown in situ on electrospinning polyacrylonitrile (PAN) microfibers (≈1.7 µm) containing urea-based linkers, followed by PAN removal via solvent extraction to obtain the hollow COF microfibers. The resultant COF FAGs possess ultralow density (14.1-15.5 mg cm-3) and hierarchical porosity that features both micro-, meso-, and macropores. Significantly, the unique interconnected structure composed of nanofibers and hollow microfibers endows the COF FAGs with unprecedented mechanical properties, which can fully recover at 50% strain and be compressed for 20 cycles with less than 5% stress degradation. Moreover, the aerogels exhibit excellent capacity for organic solvent absorption (e.g., chloroform uptake of >90 g g-1). This study opens new avenues for the design and fabrication of macroscopic COFs with excellent properties.

Lignocellulosic nanofibril aerogel via gas phase coagulation and diisocyanate modification for solvent absorption.

Cellulose-based aerogels are considered to be carriers that can absorb oils and organic solvents owing to the merits of low density and high surface area. However, the natural hydrophility and poor mechanical strength often obstruct their widespread applications. In this work, Miscanthus-based dual cross-linked lignocellulosic nanofibril (LCNF) aerogels were prepared by gas phase coagulation and methylene diphenyl dissocyanate (MDI) modification. Due to physical and chemical cross-linking strategies, the optimally 4 M-LCNF aerogels had high surface area of 157.9 m2/g, water contact angle of 138.1°, and enhanced compression properties. Moreover, the modified aerogels exhibited absorption performance for various organic solvents, and the maximal absorption capacity of chloroform was 42 g/g aerogel. Because LCNF was directly produced from Miscanthus without using bleaching reagents, this research provided a more sustainable methodology to utilize lignocelluloses to design robust aerogels to deal with the leakage of oil and organic solvents in industrial applications.

Tailoring the Performance of Graphene Aerogels for Oil/Organic Solvent Separation by 1-Step Solvothermal Approach.

Ultra-light eco-friendly graphene oxide (GO)-based aerogels are reported by simple one-step solvothermal self-assembly. The effect of varying parameters such as C/O ratio of GO; reducing agent amount; temperature; and duration on the properties of the aerogels was studied. The structural and vibrational features and hydrophobic surface properties of the obtained aerogels were obtained by XRD; FTIR; XPS; Raman; SEM; and contact angle measurements. The effect of synthesis conditions on the engine oil and organic solvent absorption properties was assessed. The results indicated that the lower the C/O ratio of GO, the better the absorption properties, with the best performance for oil uptake reaching 86 g g-1. The obtained results indicate the approach based on ice-templating and the tailoring of oxygen content in GO make the resulting aerogels potential candidates for use in oil spill and organic solvent treatments.

Bioinspired Assembly of Carbon Nanotube into Graphene Aerogel with "Cabbagelike" Hierarchical Porous Structure for Highly Efficient Organic Pollutants Cleanup.

Nowadays, physical absorption has become a feasible method offering an efficient and green route to remove organic pollutants from the industrial wastewater. Inspired by polydopamine (PDA) chemistry, one-dimensional PDA-functionalized multiwalled carbon nanotubes (MWCNT-PDA) were creatively introduced into graphene aerogel framework to synthesize a robust graphene/MWCNT-PDA composite aerogel (GCPCA). The whole forming process needed no additional reducing agents, significantly reducing the contamination emissions to the environment. The GCPCA exhibited outstanding repeatable compressibility, ultralight weight, as well as hydrophobic nature, which were crucial for highly efficient organic pollution absorption. The MWCNTs in moderate amounts can provide the composite aerogels with desirable structure stability and extra specific surface area. Meanwhile, the eventual absorption performance of GCPCAs can be improved by optimizing the microporous structure. In particular, a novel "cabbagelike" hierarchical porous structure was obtained as the prefreezing temperature was decreased to -80 °C. The miniaturization of pore size around the periphery of GCPCA enhanced the capillary flow in aerogel channels, and the super-absorption capacity for organic solvents was up to 501 times (chloroform) its own mass. Besides, the GCPCAs exhibited excellent reusable performance in absorption-squeezing, absorption-combustion, and absorption-distillation cycles according to the characteristic of different organic solvents. Because of the viable synthesis method, the resulting GCPCAs with unique performance possess broad and important application prospects, such as oil pollution cleanup and treatment of chemical industrial wastewater.