Confining Water Nanotubes in a Cu₁₀O₁₃-Based Metal–Organic Framework for Propylene/Propane Separation with Record-High Selectivity

Abstract

Energy-efficient separation of propylene (C 3 H 6 )/ propane (C 3 H 8 ) is in high demand for the chemical industry. However, this process is challenging due to the imperceptible difference in molecular sizes of these gases. Here, we report a continuous water nanotube dedicatedly confined in a Cu 10 O 13based metal−organic framework (MOF) that can exclusively adsorb C 3 H 6 over C 3 H 8 with a record-high selectivity of 1570 (at 1 bar and 298 K) among all the porous materials. Such a high selectivity originates from a new mechanism of initial expansion and subsequent contraction of confined water nanotubes (∼4.5 Å) caused by C 3 H 6 adsorption rather than C 3 H 8 . Such unique response was further confirmed by breakthrough measurements, in which one adsorption/desorption cycle yields each component of the binary mixture high purity (C 3 H 6 : 98.8%; C 3 H 8 : >99.5%) and good C 3 H 6 productivity (1.6 mL mL −1 ). Additionally, benefiting from the high robustness of the framework, the water nanotubes can be facilely recovered by soaking the MOF in water, ensuring long-term use. The molecular insight here demonstrates that the confining strategy opens a new route for expanding the function of MOFs, particularly for the sole recognition from challenging mixtures.

Optimized Pore Nanospace through the Construction of a Cagelike Metal–Organic Framework for CO2/N2 Separation

“…Recently, nonthermal-driven adsorption and separation technology based on porous solid materials has presented great potential in the CCS field due to its cost and energy efficiency, high capture capacity, and high selectivity. − In this respect, metal–organic frameworks (MOFs) have shown tremendous potential for CCS as a result of their structural diversity, function tunability, and high surface area. − Up to now, a great deal of effort has been devoted to improving the CO 2 uptake capacity and separation performance from flue gas via various crystal engineering strategies, in which pore-nanospace engineering represents an effective protocol for CCS achieved by tuning the pore size, volume, shape, and surface. − Generally, a MOF with a small pore size usually shows a high CO 2 selective adsorption performance but adversely leads to a low capture capacity, whereas a high pore volume can bestow the MOF with high uptake capacity but might reduce the adsorptive selectivity. , Therefore, engineering a MOF nanospace with the characteristics of small pore size and large pore volume might be an effective approach for achieving the trade-off between the adsorptive selectivity and uptake capacity, which can be accomplished through the construction of a cagelike MOF featuring a small window size and a large cavity. − Additionally, the window shape and internal cavity environment also play an important role in the selective adsorption process. In this regard, Feng, Zhou, and other groups have made pioneering contributions, demonstrating that pore-nanospace engineering via the construction of a cagelike MOF with suitable pore size/volume/shape/surface is an effective method to enhance the selective adsorption performance. − However, the elaborate design of a cage-based MOF with the appropriate pore volume/surface and precise window size falling between CO 2 and N 2 remains highly challenging.…”

Formation and fine-tuning of metal–organic frameworks with carboxylic pincers for the recognition of a C2H2 tetramer and highly selective separation of C2H2/C2H4

“…Adsorptive separation using porous materials is more environmentally friendly and energy efficient, and is regarded as a promising future separation technology. [6][7][8][9][10][11] As emerging porous materials, metal-organic frameworks (MOFs), derived from the self-assembly of organic ligands and inorganic nodes, demonstrate great opportunities to distinguish these two kinds of gas molecules by dedicated framework regulations, despite they have nearly identical molecular dimensions and physical properties. [12][13][14][15] For example, the MOF materials of SIFSIX-Cu-i 7 and NKMOF-1-Ni 16 exhibit minimal trade-off between adsorption capacity and selectivity, while the flexible UTSA-300 17 demonstrates gating separation of this mixtures.…”

A Robust Squarate-Cobalt Metal–Organic Framework for CO2/N2 Separation

“…Recently, the nonthermal-driven a dsorption and separation using porous solid materials based on physisorption mechanism has drawn tremendous attention due to its cost- and energy-efficiency, high uptake capacity, and selectivity. − Among these, metal–organic frameworks (MOFs) have presented great potential in the CO 2 adsorption and separation field as a result of the customized characteristics involving structural diversity, tunable functions, and high surface area. − So far, extensive research endeavors have been dedicated to developing MOF materials for CO 2 separation, in which the construction of ultra-microporous MOFs (pore diameter < 7 Å) associated with polar pore environment has been proven to be an effective approach for CO 2 separation ascribing from the enhanced confinement effect. − For instance, He and coworkers reported an ultra-microporous squarate-calcium MOF, Ca­(C 4 O 4 ) (H 2 O), for efficient CO 2 /N 2 separation via the molecular sieving effect. Zhang and coworkers developed a robust triazole-based MOF for CO 2 separation from mimic flue gas through the construction of ultra-micropore and the introduction of polar functional groups.…”