Recently, researchers have focused on preparing and studying proton exchange membranes. Metal−organic frameworks (MOFs) are candidates for composite membrane fillers due to their high crystallinity and structural characteristics, and Hf-based MOFs have attracted our attention with their high porosity and high stability. Therefore, in this study, Hf-based MOFs were doped into a costeffective chitosan matrix as fillers to fabricate composite films having excellent proton conductivity (σ). First, the nanoscale MOFs Hf-UiO-66-(OH) 2 (1) and Hf-UiO-66-NH 2 (2) were chemically modified by a ligand design strategy to obtain SA-1 and CBD-2 bearing free −COOH units. The proton conductivities of SA-1 and CBD-2 under optimal test conditions reached 1.23 × 10 −2 and 0.71 × 10 −2 S cm −1 . After that, we prepared composite membranes CS/SA-1 and CS/ CBD-2 by the casting method; tests revealed that the introduction of MOFs improved the stabilities and σ values of the membranes, and their best σ could reach above 10 −2 S cm −1 under 100 °C/98% RH. Further structural characterization and activation energy calculation revealed the conductive mechanism of the composite films. This investigation not only proposes a novel chemical modification method for optimizing the σ of MOFs but also promotes the development of MOF-doped composite membranes and provides a basis for future applications of MOFs in fuel cells.

Assembling crystalline materials with high stability and high proton conductivity as a potential alternative to the Nafion membrane is a challenging topic in the field of energy materials. Herein, we concentrated on the creation and preparation of hydrazone-linked COFs with super-high stability to explore their proton conduction. Fortunately, two hydrazone-linked COFs, TpBth and TaBth, were solvothermally prepared by using benzene-1,3,5-tricarbohydrazide (Bth), 2,4,6-trihydroxy-benzene-1,3,5tricarbaldehyde (Tp), and 2,4,6-tris(4-formylphenyl)-1,3,5-triazine (Ta) as monomers. Their structures were simulated by Material Studio 8.0 software and confirmed by the PXRD pattern, demonstrating a two-dimensional framework with AA packing. The presence of a large number of carbonyl groups as well as −NH−NH 2 − groups on the backbone is responsible for their super-high water stability as well as high water absorption capacity. AC impedance tests demonstrated a positive correlation between the waterassisted proton conductivity (σ) of the two COFs and the temperature and humidity. Under 100 °C/98% RH, the highest σ values of TpBth and TaBth can reach 2.11 × 10 −4 and 0.62 × 10 −5 S•cm −1 , which are among the high σ values of the reported COFs. Their proton-conductive mechanisms were highlighted by structural analyses as well as N 2 and H 2 O vapor adsorption data and activation energy values. Our systematic research affords ideas for the synthesis of proton-conducting COFs with high σ values.

This work elucidates the potential impact of intramolecular H‐bonds within the pore walls of covalent organic frameworks (COFs) on proton conductivity. Employing DaTta and TaTta as representative hosts, it was observed that their innate proton conductivities (σ) are both unsatisfactory and σ(DaTta) < σ(TaTta). Intriguingly, the performance of both imidazole‐loaded products, Im@DaTta and Im@TaTta is greatly improved, and the σ of Im@DaTta (0.91 × 10‐2 S·cm‐1) even surpasses that of Im@TaTta (3.73 × 10‐3 S·cm‐1) under 100 °C and 98% relative humidity. The structural analysis, gas adsorption tests, and activation energy calculations forecast the influence of imidazole on the H‐bonded system within the framework, leading to observed changes in proton conductivity. It is hypothesized that intramolecular H‐bonds within the COF framework impede efficient proton transmission. Nevertheless, the inclusion of an imidazole group disrupts these intramolecular bonds, leading to the formation of an abundance of intermolecular H‐bonds within the pore channels, thus contributing to a dramatic increase in proton conductivity. The related calculation of Density Functional Theory (DFT) provides further evidence for this inference.

Fluid-solid coupling simulation experiment is an important method for studying water inrush from the coal seam floor. However, the experiment involves seepage-stress coupling problems, and most existing fluid-solid coupling model experiment systems do not meet sealing requirements. To address this issue and to successfully conduct the model experiment, a novel similitude experimental model with excellent sealing was developed for studying fluid-solid coupling during water inrush from the floor of the coal seam. Similitude relationships were also derived using mathematical models for fluid-solid coupling in homogeneous continuum media, and non-hydrophilic fluid-solid coupling similitude materials were prepared. Results show that the experimental system can be used to analyse the variation characteristics of the floor stress and the water pressure, and the mining-induced floor stresses can be divided into three distinct stages, such as the pre-mining stress-increasing stage, the post-mining stress-decreasing stage, and the stress recovery stage. The conclusions obtained in the study have important theoretical value to direct the similar engineering practice.