Search

Adsorptive separation of Xe and Kr is an industrially promising but challenging process because of their identical shape and similar physicochemical properties. Herein, we demonstrate a strategy through rationally designing the linkers of anionic functional ultramicroporous materials (FUMs) to finely regulate the pore chemistry and architecture, which creates unique stepped channels incorporating dense polar nanotraps to generate a larger effective pore space and enables dense packing of Xe. A new hydrolytically stable FUM (ZUL-530) was prepared, which for the first time achieves a Xe packing density exceeding the liquid Xe density at atmospheric conditions in metal−organic frameworks (MOFs) (based on experimental data), resulting in both excellent Xe uptake (2.55 mmol g–1at 0.2 bar) and high IAST selectivity (20.5). GCMC and DFT-D calculations reveal the essential role of the stepped traps in the dense packing of Xe. Breakthrough experiments demonstrate remarkable productivities of both high-purity Kr (6.70 mmol g–1) and Xe (1.78 mmol g–1) for the Xe/Kr (20:80) mixture. In a model nuclear industry exhaust gas, ZUL-530 exhibits a top-class Xe dynamic capacity (28.8 mmol kg–1) for trace Xe, which proves it is one of the best candidates for Xe/Kr separation.

Developing adsorbents with multiple merits in capacity, selectivity, mass transfer, and stability toward C2H2/CO2separation is crucial and challenging for producing high-purity C2H2for advanced polymers and the electronic industry. Here, we demonstrate a vertex strategy to create adsorbents combining these merits through rationally designing the vertex groups of a wavy-shaped framework in layered 2D metal–organic frameworks (MOFs) to finely regulate the local conformation and stacking interactions, which creates the optimal inter- and intralayer space to realize simultaneous improvement of adsorption thermodynamics and kinetics. Two new hydrolytically stable MOFs, ZUL-330 and ZUL-430, were prepared, and diverse experiments and modeling on both adsorption equilibrium and diffusion were performed. Record separation selectivities coupled with extraordinary dynamic C2H2capacities were achieved for C2H2/CO2mixtures with different proportions (50/50 or 10/5, v/v), along with a small diffusion barrier and fast mass transfer. Consequently, polymer-grade (99.9%) and electronic-grade (99.99%) C2H2were obtained with excellent productivities of up to ∼6 mmol cm–3.

Selective elimination of sulfur dioxide is significant in flue gas desulfurization and natural gas purification, yet developing adsorbents with high capture capacity especially at low partial pressure as well as excellent cycling stability remains a challenge. Herein, a family of isostructural gallate-based MOFs with abundant hydrogen bond donors decorating the pore channel was reported for selective recognition and dense packing of sulfur dioxide via multiple hydrogen bonding interactions. Multiple O···H–O hydrogen bonds and O···H–C hydrogen bonds guarantee SO2molecules are firmly grasped within the framework, and appropriate pore apertures afford dense packing of SO2with high uptake and density up to 1.86 g cm–3, which is evidenced by dispersion-corrected density functional theory calculations and X-ray diffraction resolution of a SO2-loaded single crystal. Ultrahigh adsorption uptake of SO2at extremely low pressure (0.002 bar) was achieved on Co-gallate (6.13 mmol cm–3), outperforming all reported state-of-the-art MOFs. Record-high IAST selectivity of SO2/CO2(325 for Mg-gallate) and ultrahigh selectivity of SO2/N2(>1.0 × 104) and SO2/CH4(>1.0 × 104) were also realized. Breakthrough experiments further demonstrate the excellent removal performance of trace amounts of SO2in a deep desulfurization process. More importantly, M-gallate shows almost unchanged breakthrough performance after five cycles, indicating the robust cycling stability of these MOFs.

The adsorptive separation of propylene and propane offers an energy-efficient alternative to the conventional cryogenic distillation technology. However, developing porous adsorbents with both high equilibrium and kinetic selectivity remains extremely challenging due to the similar size and physical properties of these gases. Herein, this work reports a ligand racemization strategy to construct quasi-discrete pores in MOFs for a synergistically enhanced thermodynamic and kinetic separation performance. The use of enantiopure l-malic acid versus racemic dl-malic acid as ligands afforded isoreticular Ni-based MOFs with contrasting one-dimensional channels (l-mal-MOF) and quasi-discrete cavities connected by small windows (dl-mal-MOF). The periodic pore constrictions in dl-mal-MOF significantly increased the differentiation in diffusion rates and binding energies between propylene and propane. dl-mal-MOF exhibited an exceptional propylene uptake of 1.82 mmol/g at 0.05 bar and 298 K along with an ultrahigh equilibrium–kinetic combined selectivity of 62.6. DFT calculations and MD simulations provided insights into the synergistic mechanism of preferential propylene adsorption and diffusion. Breakthrough column experiments demonstrated the excellent separation and high-purity recovery of propylene over propane on dl-mal-MOF. The robust stability and facile regeneration highlight its potential for propylene purification applications.