Flexible Hyper-Cross-Linked Polymers Knitted by OTs-Based Cross-Linkers and Their Pressure-Induced Gate-Opening Methane Adsorption

Flexible hyper-cross-linked polymers (HCPs) exhibit unique dynamic properties compared to their rigid counterparts, yet their synthesis remains challenging due to the inherent reactivity limitations of long-chain cross-linkers. In this work, we address the critical gaps in the synthetic difficulty in incorporating flexibility into HCPs and poorly understood structure–property relationships in flexible HCP systems. We report a novel strategy employing highly active p-toluenesulfonate (OTs)-terminated long-chain aliphatic cross-linkers to construct flexible HCPs with tunable dynamic behavior. Comprehensive characterization revealed two distinctive phenomena: pore collapse at ambient pressure and the pressure-induced gate-opening effect, as demonstrated through nitrogen sorption and methane storage experiments (measured up to 100 bar). The flexible HCPs exhibit pressure-responsive pore expansion, transitioning from contracted or even closed states at low pressure to expanded states at elevated pressures, achieving an exceptional methane working capacity of 251 cm3 (STP) cm–3 at 273 K and 5–100 bar, surpassing most reported rigid porous polymers. This study establishes a universal design principle for flexibility control in HCPs through OTs-based cross-linker length variation based on various building blocks and provides fundamental insights into dynamic structure–property relationships, paving the way for advanced applications of stimuli-responsive porous polymers.