Design of Pore Properties of an Al-Based Metal-Organic Framework for the Separation of an Ethane/Ethylene Gas Mixture via Ethane-Selective Adsorption

Insights into the Imprinting and Rebinding Performance of Molecularly Imprinted Hybrids for Bisphenol A and Bisphenol F

This study investigates the factors influencing the imprinting performance of molecularly imprinted hybrids (MIHs) with various template/monomer associations and their corresponding adsorption ability for three bisphenol analogues, bisphenol A (BPA), 2,2'-bisphenol F (2BPF), and 4,4'-bisphenol F (4BPF). Styrene (St) and methacrylic acid (MAA) were selected as the primary functional monomers for template complexation. Compared with hydrophilic MAA monomers, hydrophobic St monomers were more favorable for BPA imprinting, despite the lower binding energy of π-π interactions compared to hydrogen bonds. However, St monomers were unsuitable for 4BPF imprinting, while 2BPF exhibited limited complexation with MAA monomers. Among the bisphenols, BPA demonstrated the strongest imprinting capability, leading MIHs to exhibit the highest imprinting factor (IF = 14-18), adsorption capacity (Qmax = 43.7-47.6 mg/g), binding affinity (KL = 4.52-6.74 L/mg, ΔHads° = -35.2 to -38.9 kJ/mol, and ΔSads° = -40.5 to -50.6 J mol-1 K-1), and selectivity over 2BPF and 4BPF (2.0-3.5). In contrast, 2BPF- and 4BPF-imprinted hybrids exhibited significantly lower adsorption capacities (Qmax = 19.4-26.7 mg/g) and binding affinities (KL = 1.22-4.35 L/mg) for their respective templates. In competitive adsorption systems, bisphenol rebinding followed the trend BPA > 2BPF > 4BPF, regardless of which template was used for imprinting. Based on NMR analysis, the superior structure-directing and competitive rebinding abilities of BPA are attributed to the restricted rotation of its two phenyl groups, p-OH groups, and additional -CH3 groups on the bridged carbon, which enhance π-π stacking, H-bond, CH-π, and hydrophobic interactions within the imprinted cavities. In contrast, the o-OH groups of 2BPF and the rotational phenyl groups of 4BPF hinder their imprinting and rebinding via H-bond and π-π interactions, respectively.

A Stable Layered Microporous MOF Assembled with Y-O Chains for Separation of MTO Products

Benefiting from highly tunable pore environments, some metal-organic frameworks (MOFs) have recently shown promising prospects in the separation of methanol-to-olefin (MTO) products (mainly C3H6 and C2H4). However, the "trade-off" between gas storage capacity and selectivity always results in inefficient separation. In addition, poor stability of MOFs also limits practical separation applications. Herein, we have successfully assembled a layered Y-MOF (FJI-W9) with bent diisophthalate ligands (H4L), Y-O chains, and 2-fluorobenzoic acids. As expected, FJI-W9 not only exhibits good chemical stability but also shows significant potential for C3H6/C2H4 separation. For FJI-W9, the C3H6 uptake at 298 K and 10 kPa is 63 cm3/g, and the IAST selectivity of FJI-W9 for C3H6/C2H4 (V/V = 50/50) is calculated to be 20.5. To the best of our knowledge, both C3H6 uptake and selectivity of FJI-W9 surpass most porous materials. GCMC simulation indicates that the special supramolecular binding sites in FJI-W9 have much stronger interactions with C3H6 than C2H4 molecules. More importantly, practical breakthrough experiments demonstrate that FJI-W9 can effectively separate C3H6/C2H4 (50/50) mixtures, thus obtaining high-purity C2H4 and C3H6, respectively.

Separation of High-Purity C2H2 from Binary C2H2/CO2 Using Robust Al-Based MOFs Comprising Nitrogen-Containing Heterocyclic Dicarboxylate

In this study, three nitrogen-containing aluminum-based metal-organic frameworks (Al-MOFs), namely, CAU-10pydc, MOF-303, and KMF-1, were investigated for the efficient separation of a C2H2/CO2 gas mixture. Among these three Al-MOFs, KMF-1 demonstrated the highest selectivity for C2H2/CO2 separation (6.31), primarily owing to its superior C2H2 uptake (7.90 mmol g-1) and lower CO2 uptake (2.82 mmol g-1) compared to that of the other two Al-MOFs. Dynamic breakthrough experiments, using an equimolar binary C2H2/CO2 gas mixture, demonstrated that KMF-1 achieved the highest separation performance. It yielded 3.42 mmol g-1 of high-purity C2H2 (>99.95%) through a straightforward desorption process under He purging at 298 K and 1 bar. To gain insights into the distinctive characteristics of the pore surfaces of structurally similar CAU-10pydc and KMF-1, we conducted computational simulations using canonical Monte Carlo and dispersion-corrected density functional theory methods. These simulations revealed that the secondary amine (C2N-H) groups in KMF-1 played a more significant role in differentiating between C2H2 and CO2 compared to that of the N atoms in CAU-10pydc and MOF-303. Consequently, KMF-1 emerged as a promising adsorbent for the separation of high-purity C2H2 from binary C2H2/CO2 gas mixtures.