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.

High Pore Volume Hyper-Cross-Linked Polymers via Mixed-Solvent Knitting: A Route to Superior Hierarchical Porosity for Methane Storage and Delivery

“…The elemental composition and content of the polymers were investigated by elemental analysis of HCPs-MS. As shown in Table S2, all HCPs were composed primarily of the elements carbon (C) and hydrogen (H), in agreement with previous literature findings . Notably, the elemental carbon content increased from 80.86% in HCP-MS-1 to 92.17% in HCP-MS-5, while the hydrogen content increased from 5.64 to 6.72% in the same polymers.…”

“…This variation can be related to the significant presence of methylene (−CH 2 −) and S2, all HCPs were composed primarily of the elements carbon (C) and hydrogen (H), in agreement with previous literature findings. 10 Notably, the elemental carbon content increased from 80.86% in HCP-MS-1 to 92.17% in HCP-MS-5, while the hydrogen content increased from 5.64 to 6.72% in the same polymers. This gradual shift in hydrogen content (5.64−6.72%) correlated with the increase in the volumetric ratio of DCE in the mixed solvents.…”

“…Additionally, the smaller peaks around 3028 cm −1 are indicative of the C−H stretching vibrations within the benzene ring, and peaks at 1633, 1450, and 1382 cm −1 represent the stretching vibrations of the aryl ring skeleton, which can be observed in both polymers and their building block (Figure S1). Moreover, distinct absorption peaks only observed in the polymers at 2966, 2925, and 2860 cm The chemical structure of HCPs-MS was meticulously analyzed through solid-state 13 C CP/MAS NMR spectroscopy. Figure 1b illustrates that these spectra with three predominant resonance peaks located at approximately 140, 131, and 36 ppm.…”

“…34 Instead, HCPs exhibit better structural stability than MOFs due to their highly robust covalent bonding via the irreversible Friedel−Crafts alkylation reaction, making them more conducive to high-pressure methane storage and delivery in long-term practical applications. 13 Despite limited work that has explored HCPs as methane adsorbents, there is an ongoing focus on optimizing surface areas and achieving high pore volumes. Cooper et al 35 synthesized a series of powder and bulk HCPs by self-condensation of dichloromethyl monomers, in which bulk HCP-4 with a micropore volume of 0.54 cm 3 g −1 exhibited a methane adsorption capacity of 0.106 g g −1 at 298 K and 100 bar.…”

Fabrication of dianthracene-based hyper-cross-linked polymers for selective photocatalytic oxidation of organic sulfides

“…Generally speaking, larger monomers may provide more reactant sites, and the introduction of lightweight elements (C, H, and N) can also increase the BET surface area of HCPs. 50 However, HCP-DiBrAn is more porous than HCP-DiAn despite the addition of Br, which prompts us to explore the structural difference caused by monomer solubility. In general, the porosity of HCPs depends on the expansion of methylene groups (linkage), which is determined using the degree of cross-linking.…”