Porosity Engineering of Hyper-Cross-Linked Polymers Based on Fine-Tuned Rigidity in Building Blocks and High-Pressure Methane Storage Applications

Abstract

Exploring the effect of the structural rigidity of selected building blocks on the resultant porosity of the desired polymers is crucial for the bottom-up design of hyper-cross-linked polymers. Herein, several novel polymers, based on two series building blocks with stepwise fine-tuned rigidity, were constructed by the low-cost solvent knitting method. Significantly, the porosity of these polymers is highly consistent with the structural rigidity of the basic building blocks, dramatically enhanced from a poor porous state to a micropore-rich framework, with an increase in BET surface areas from 248 to 1276 m2 g–1 for the HCPs based on monomers containing double benzene rings and from 37 to 2368 m2 g–1 for tetraphenyl-like monomer-based HCPs. The best performances, especially concerning methane adsorption capacity, are reached for the rigid 9,9′-spirobifluorene (SBF)-based HCP-SBF framework and flexible tetraphenylmethane (TPM)-based HCP-TPM, showing a 5–100 bar working capacity of 206 cm3 (STP: 273 K, 1 atm) cm–3 (0.296 g g–1) and 199 cm3 (STP) cm–3 (0.112 g g–1) at 273 K, respectively. The bottom-up-designed HCPs with engineered porosity are expected to become novel candidates for onboard methane storage.