Engineering Pore Environments of Sulfate‐Pillared Metal‐Organic Framework for Efficient C₂H₂/CO₂ Separation with Record Selectivity

Abstract

Engineering pore environments exhibit great potential in improving gas adsorption and separation performances but require specific means for acetylene/carbon dioxide (C2H2/CO2) separation due to their identical dynamic diameters and similar properties. Herein, a novel sulfate‐pillared MOF adsorbent (SOFOUR‐TEPE‐Zn) using 1,1,2,2‐tetra(pyridin‐4‐yl) ethene (TEPE) ligand with dense electronegative pore surfaces is reported. Compared to the prototype SOFOUR‐1‐Zn, SOFOUR‐TEPE‐Zn exhibits a higher C2H2 uptake (89.1 cm3 g−1), meanwhile the CO2 uptake reduces to 14.1 cm3 g−1, only 17.4% of that on SOFOUR‐1‐Zn (81.0 cm3 g−1). The high affinity toward C2H2 than CO2 is demonstrated by the benchmark C2H2/CO2 selectivity (16 833). Furthermore, dynamic breakthrough experiments confirm its application feasibility and good cyclability at various flow rates. During the desorption cycle, 60.1 cm3 g−1 C2H2 of 99.5% purity or 33.2 cm3 g−1 C2H2 of 99.99% purity can be recovered by stepped purging and mild heating. The simulated pressure swing adsorption processes reveal that 75.5 cm3 g−1 C2H2 of 99.5+% purity with a high gas recovery of 99.82% can be produced in a counter‐current blowdown process. Modeling studies disclose four favorable adsorption sites and dense packing for C2H2.

Recent progress in metal–organic frameworks for the separation of gaseous hydrocarbons

“…Although CO 2 and C 2 H 2 have similar sizes (CO 2 : 3.18 × 3.33 × 5.36 Å 3 , and C 2 H 2 : 3.32 × 3.34 × 5.7 Å 3 ) and physical properties (boiling point of CO 2 = 194.7 K and of C 2 H 2 = 189.3 K), the opposite quadrupole moments and slightly discrepant polarizabilities between C 2 H 2 and CO 2 , as well as the stronger π-bonding ability with metal sites and hydrogen-bonding donor ability of C 2 H 2 , allow the realization of their separation by means of rational design of pore surfaces and flexible framework amplification. 72,95–98…”

“…It is well known that pore size and shape play an important role in the separation process, as an appropriate pore size can enhance the strength of interactions between the pore surface and adsorbate, as well as among adsorbates themselves. 97,100,112,117–123 MOFs can be designed and modified to alter the pore sizes, even at the sub-nanometer scale, through substitutions of metal ions, organic ligands, or inorganic anions. Strategies such as building self-interpenetrated networks and pore space partition (PSP) can also be used for the pore size or space modulation.…”

“…10). 97 SOFOUR-TEPE-Zn is an isostructural framework with SOFOUR-1-Zn, 128 but with more electron-rich pore surfaces due to the higher electronegative ethylene groups in the TEPE ligand in contrast to the phenyl ring in the TEPB ligand. Single-component sorption results of SOFOUR-TEPE-Zn reveled a higher C 2 H 2 uptake (89.1 cm 3 g −1 , 3.98 mmol g −1 ) than SOFOUR-1-Zn (69.4 cm 3 g −1 , 3.10 mmol g −1 ) at 1 bar and 298 K, but a much lower CO 2 uptake (14.1 cm 3 g −1 , 0.63 mmol g −1 ), resulting in a very high IAST selectivity of 16833 for 50/50 C 2 H 2 /CO 2 .…”

Synthesis and up-to-date applications of 2D microporous g-C3N4 nanomaterials for sustainable development

“…[17][18][19][20][21] Specifically, as shown in the Fig. 1, the main 2D materials are graphene, 22 graphene oxide (GO), 23 boron nitride (BNs), 24 metal organic frameworks (MOFs), 25 covalent organic frameworks (COFs), 26 transition metal carbides and nitrides (MXenes) 6 and g-C 3 N 4 , etc. 27 These materials are playing an increasingly important role in sustainable research.…”

Computational Simulation of CO2/CH4 Separation on a Three-Dimensional Cd-Based Metal–Organic Framework

“…MOFs are porous inorganic materials that have received much attention recently owing to their outstanding characteristics, such as significant surface area and porosity, thermal/chemical stability, and tunability. − MOFs are considered promising materials for a variety of potential applications across various fields, including gas storage and separation, chemical sensing, biomedical applications, adsorption, and heterogeneous catalysis. − They are considered as one of the most promising physical adsorbent materials in the process of separating CO 2 /CH 4 . The engineering design of MOFs for gas separation applications is currently a rapidly growing area of research. − Numerous experimental and simulation-based studies have been documented involving the separation of CO 2 from CH 4 through the use of MOFs. − Considering the quadrupole moment and polarizability of CO 2 , current research efforts to enhance CO 2 uptake and selectivity primarily involves strategies aimed at improving the interaction between CO 2 and the frameworks. These include, but are not limited to, the utilization of various open metal sites, the insertion of functional groups, , the development of smart adsorbents, and ligand shortening in MOFs. , An investigation showed that MOF-801­(Ce) displayed improved separation performance for CO 2 /N 2 and CO 2 /CH 4 compared to MOF-801­(Zr/Hf) .…”