Modulating Pore-Surface Adsorption in Covalent Organic Frameworks for Superior Hydrogen Storage

Three-dimensional covalent organic frameworks (3D COFs) offer high surface areas and diverse microstructures for gas adsorption, yet their hydrogen storage is limited by weak host–guest interactions in physisorption. Here, we report a microstructural tuning strategy using an N–N-containing hydrazine monomer to simultaneously minimize pore size and enhance pore-surface interactions with hydrogen. The resulting HZ-Si-COF features ultramicropores of 0.8 nm and abundant nitrogen sites with excess charges, which induce H2 polarization and yield a high adsorption heat. Consequently, HZ-Si-COF achieves 2.22 wt % H2 uptake at 77 K and 1 bar and 5.00 wt % at 70 bar, with excellent cycling stability under high pressure. This study demonstrates that strengthening pore-surface induction via structural design is an effective route to improving gas adsorption, providing insights for the development of COFs with superior hydrogen storage capabilities.