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As a class of crystalline porous polymers, covalent organic frameworks (COFs) have shown great application potential in electrochemical energy storage due to their high specific surface area, porous structure, and multiple redox-active sites. However, there are some challenges for practical application of COFs, such as low electrical conductivity, easy stacking, weak mechanical strength, and poor processability. In this study, 2,6-diaminoanthraquinone (DAAQ)-1,3,5-triformylphloroglucinol (TFP) COF is synthesized on dialdehyde cellulose fibers (DACF) with hyperbranched polyamide-amine (HPAMAM) as a stabilizer. After carbonization, the COF is uniformly and stably supported on the conductive carbon fibers (CCF) for preparing composite paper electrode (CCF/HPAMAM/COF paper). The carbonized fibers provide mechanical support for COF and improve the electron transfer efficiency. While the COF layers shorten the ion diffusion path for high utilization of redox-active sites due to its porous structure. The CCF/HPAMAM/COF paper exhibits high volume specific capacitance (66.7 F cm-3at 0.5 mA cm-2), good rate capability (capacitance retention of 82% with 10 times current density), and long lifetime (charge-discharge stability of 93.7% after 10000 cycles). This work develops a carbonized paper-supported electrode with stable loading of COFs on carbonized fibers for new generation sustainable supercapacitors.

The present paper aims to establish a versatile strength theory suitable for elasto-plastic analysis of underground tunnel surrounding rock. In order to analyze the effects of intermediate principal stress and the rock properties on its deformation and failure of rock mass, the generalized nonlinear unified strength theory and elasto-plastic mechanics are used to deduce analytic solution of the radius and stress of tunnel plastic zone and the periphery displacement of tunnel under uniform ground stress field. The results show that: intermediate principal stress coefficient bhas significant effect on the plastic range, the magnitude of stress and surrounding rock pressure. Then, the results are compared with the unified strength criterion solution and Mohr–Coulomb criterion solution, and concluded that the generalized nonlinear unified strength criterion is more applicable to elasto-plastic analysis of underground tunnel surrounding rock.