Tuning Pore Size in Square‐Lattice Coordination Networks for Size‐Selective Sieving of CO₂

Abstract

Porous materials capable of selectively capturing CO 2 from flue-gases or natural gas are of interest in terms of rising atmospheric CO 2 levels and methane purification. Sizeexclusive sieving of CO 2 over CH 4 and N 2 has rarely been achieved. Herein we show that acrystal engineering approach to tuning of pore-size in ac oordination network, [Cu(quinoline-5-carboxyate) 2 ] n (Qc-5-Cu)ena+bles ultra-high selectivity for CO 2 over N 2 (S CN % 40 000) and CH 4 (S CM % 3300). Qc-5-Cu-sql-b,anarrowpore polymorph of the square lattice (sql) coordination network Qc-5-Cu-sql-a, adsorbs CO 2 while excluding both CH 4 and N 2 .E xperimental measurements and molecular modeling validate and explain the performance. Qc-5-Cu-sql-b is stable to moisture and its separation performance is unaffected by humidity.

Metal–Organic Frameworks for Separation

“…With a similar approach, Zhang and co‐workers studied the CO 2 capture on a square lattice type 2D coordination network named Qc‐5‐Cu‐sql . There are two forms of this compound, the solvated form (Qc‐5‐Cu‐sql‐α) with a pore size of ≈3.8 Å and a desolvated one (Qc‐5‐Cu‐sql‐β) with pore size of ≈3.3 Å.…”

A highly stable metal‐organic framework with optimum aperture size for CO2 capture

“…Considering the ultrasmall aperture size and enhanced pore wall polarity brought by the dangling hydroxyl groups, which have been proven to be highly favorable for CO 2 adsorption, 25,26 the low-pressure gas sorption properties of opt-UiO-66(Zr)-(OH) 2 were studied by conducting gas sorption tests at 273 K and 298 K, respectively, with pressures up to 1 bar (Figure 2c and Supporting Information Figure S4). Opt-UiO-66(Zr)-(OH) 2 demonstrates a high CO 2 working capacity [defined as the CO 2 uptake capacity difference between adsorption at $0.15 bar (partial pressure of CO 2 in flue gas) and desorption at $0 bar] of 2.50 mmol g 21 , which is 575 and 38% higher than that of UiO-66(Zr) (0.37 mmol g 21 ) and UiO-66(Hf)-(OH) 2 (1.81 mmol g 21 ), respectively.…”

“…24 Recently, it has been found that adsorbents with appropriate pore size can be suitable candidates for CO 2 capture. For example, Zaworotko and coworkers reported a series of SIFSIX-based MOFs with ultra-small pore size (as low as 3 Å ) and hydrophobic interiors for postcombustion CO 2 capture, 25 direct air CO 2 capture, 26,27 and hydrocarbon separations. 28,29 Vaidhyanathan and coworkers exquisitely designed a MOF, Ni-(4-pyridylcarboxylate) 2 , with an aperture size of 3.5-4.8 Å , which exhibits high CO 2 /H 2 separation performance for precombustion CO 2 capture.…”

An Ultrastable Metal Azolate Framework with Binding Pockets for Optimal Carbon Dioxide Capture

“…[6,7] To satisfy the urge of achieving both high uptake capacity/selectivity and low energy penalty,significant advances are made concerning the development of two important types of MOF adsorbents in the recent decade. [8][9][10][11][12][13][14][15] First, the success of MOF-74 (CPO-27) and related materials brought forward the role of open metal sites in efficient carbon capture. [8][9][10][11] Thestrong interaction with CO 2 molecules is the key to high selectivity in gas separation, especially when the exposed metal sites are appended with amines (as in mmen-Mg 2 (dobpdc)) [10] or hydroxide (as in MAF-X25ox).…”

“…Second, later on, af amily of pillared-square-grid metal-organic materials, namely SIFSIX-n and analogues,w ere developed by taking advantage of pore size selectivity in gas separation. [12][13][14][15] In the cases of SIFSIX-3-Cu [13] and Qc-5-Cu-sql-b, [15] the pore sizes were judiciously engineered to achieve ultrahigh selectivity and also lower the energy costs for regeneration, but ac ompromise in uptake capacity is inevitable.F urthermore, the related NbOFFIVE-1-Ni was demonstrated to be stable toward moisture and highly efficient for CO 2 capture under fuel gas stream [7] and direct air capture conditions. [14] At hird, sporadic type of MOF adsorbents also exhibited excellent ability for carbon dioxide capture,which was mainly attributed to their collective binding sites,a sexemplified by Zn 2 (Atz) 2 (ox), [16] NOTT-300, [17] UTSA-16, [18] and MAF-23.…”