Rigid Ladder-Type Porous Polymer Networks for Entropically Favorable Gas Adsorption

To improve methane storage capacity of porous organic materials, this work demonstrates that a rigid ladder-type backbone is more entropically favorable for gas adsorption and leads to a high gas uptake per unit surface area. A porous ladder polymer network was designed and synthesized as the model material via cross-coupling polymerization and subsequent ring-closing olefin metathesis, followed by characterization by solid-state nuclear magnetic resonance (NMR) spectroscopy. This material exhibited a remarkable methane uptake per unit surface area, which outperformed those of most reported porous organic materials. Variable-temperature thermodynamic adsorption measurements corroborated the significantly less negative entropy penalty during high-pressure gas adsorption, compared to its non-ladder-type counterpart. This method provides an orthogonal strategy for multiplying volumetric methane uptake capacity of porous materials. The entropic approach also offers the opportunity to increase deliverable gas ...