Bin Wang

The separation of ethane (C₂H₆) from methane (CH₄) is a pivotal process for increasing the calorific value of natural gas, but technically challenging due to their similar physical properties. Adsorbent-based gas separation methods utilizing metal-organic frameworks (MOFs) offer distinct advantages, yet their insufficient efficiency and stability limit their practical applications. Herein, we present a novel stable hafnium-based MOF (Hf-MOF), Hf-H₃CTTA-3COOH, constructed from a tritopic carboxylic acid ligand that incorporates high-density uncoordinated carboxylic groups attached to the central benzene ring, and further investigate its adsorption separation properties and mechanisms for C₂H₆/CH₄ mixtures. Featuring abundant aromatic rings and uncoordinated carboxyl oxygen atoms in its octahedral cages, Hf-H₃CTTA-3COOH exhibits denser and stronger C-H···π and C-H···O interactions with C₂H₆ than with CH₄. This results in an outstanding selectivity of Hf-H₃CTTA-3COOH for C₂H₆/CH₄, reaching 11.8, which is superior to many reported materials. Breakthrough experiments verified the excellent reusability and practical C₂H₆/CH₄ separation feasibility of Hf-H₃CTTA-3COOH. The mechanisms are investigated through the GCMC analysis. The results of this study underscore the promising utility of Hf-H₃CTTA-3COOH as an effective adsorbent for producing high-purity CH₄.

Two Zn-triazolate frameworks, DZU-109 and DZU-110, where DZU-110 exhibits excellent I₃⁻ adsorption in water due to its open Zn²⁺ sites.

There is an urgent need for highly efficient sorbents capable of selectively removing ⁹⁹TcO₄^- from concentrated alkaline nuclear wastes, which has long been a significant challenge. In this study, we present the design and synthesis of a high-performance adsorbent, CPN-3 (CPN denotes cationic polymeric nanotrap), which achieves excellent ⁹⁹TcO₄^- capture under strong alkaline conditions by incorporating branched alkyl chains on the N3 position of imidazolium units and optimizing the framework anion density within the pores of a cationic polymeric nanotrap. CPN-3 features exceptional stability in harsh alkaline and radioactive environments as well as exhibits fast kinetics, high adsorption capacity, and outstanding selectivity with full reusability and great potential for the cost-effective removal of ⁹⁹TcO₄^-/ReO₄^- from contaminated water. Notably, CPN-3 marks a record-high adsorption capacity of 1052 mg/g for ReO₄^- after treatment with 1 M NaOH aqueous solutions for 24 h and demonstrates a rapid removal rate for ⁹⁹TcO₄^- from simulated Hanford and Savannah River Site waste streams. The mechanisms for the superior alkaline stability and ⁹⁹TcO₄^- capture performances of CPN-3 are investigated through combined experimental and computational studies. This work suggests an alternative perspective for designing functional materials to address nuclear waste management.

Highly efficient adsorptive separation of propylene from propane offers an ideal alternative method to replace the energy-intensive cryogenic distillation technology. Molecular sieving-type separation via high-performance adsorbents is targeted for superior selectivity, but the limit in adsorption capacity remains a great challenge. Here, we report an oxyfluoride-based ultramicroporous metal-organic framework UTSA-400, [Ni(WO₂F₄)(pyz)₂] (pyz = pyrazine), featuring one-dimensional pore channels that can accommodate the propylene molecules with optimal binding affinity while specifically excluding the propane molecules. The exposed oxide/fluoride pairs in UTSA-400 serve as strong functional sites for strengthened propylene-host interactions, accounting for a significantly enhanced propylene uptake, while the propane molecules are excluded due to the regulated host framework dynamics. The strong propylene binding enables near-saturation of propylene in the pore confinement at ambient conditions, leading to full utilization of pore space and superior packing density. Combined in situ infrared spectroscopy measurements and dispersion-corrected density functional theory calculations clearly unveil the nature of boosted host-guest binding. Direct production of polymer-grade (>99.5%) propylene with remarkable dynamic productivity is demonstrated by column breakthrough experiments. This work presents an example of pore engineering with atomic precision to break the trade-off in adsorptive separation through guest binding optimization.

A novel microporous indium-based MOF material with unique 3-way rod-shaped secondary building units (SBUs), UTSA-22, was reported and exhibited high methane (CH₄) and hydrogen (H₂) storage. At 298 K and 65 bar, the total CH₄ volumetric uptake of UTSA-22 is 174 cm³(STP) cm⁻³. Moreover, UTSA-22 shows a high CH₄ working capacity of 146 cm³(STP) cm⁻³ in a pressure range of 5–65 bar at 298 K. In addition, UTSA-22 shows a high H₂ gravimetric storage capacity (1.2 wt%) at 298 K and 100 bar.

A copper-based metal–organic framework, [Cu₂(PBTDA)(H₂O)₂] (UTSA-98, UTSA = the University of Texas at San Antonio; H₄PBTDA = 5′,5′′′′-(1,4-phenylene)bis([1,1′:3′,1″-terphenyl]-4,4″-dicarboxylic acid)), has been solvothermally synthesized. The alternative connection of classical dicopper secondary building units and deprotonated four-branched PBTDA^4– ligands led to the formation of the three-dimensional framework of UTSA-98 with one-dimensional rhombic channels. Its guest-free phase, UTSA-98a, uptakes much more C₂H₂ (82.6 cm³/g) than CO₂ (40.3 cm³/g) at 298 K and 100 kPa, resulting in a high adsorption selectivity of 5.2. Furthermore, the efficient separation ability of UTSA-98a toward the C₂H₂/CO₂ gas mixture was further verified by laboratory-scale fixed-bed breakthrough experiments.