Robust Ultramicroporous Metal–Organic Frameworks with Benchmark Affinity for Acetylene

Abstract

Highly selective separation and/or purification of acetylene from various gas mixtures is a relevant and difficult challenge that currently requires costly and energy-intensive chemisorption processes. Two ultramicroporous metal-organic framework physisorbents, NKMOF-1-M (M=Cu or Ni), offer high hydrolytic stability and benchmark selectivity towards acetylene versus several gases at ambient temperature. The performance of NKMOF-1-M is attributed to their exceptional acetylene binding affinity as revealed by modelling and several experimental studies: in situ single-crystal X-ray diffraction, FTIR, and gas mixture breakthrough tests. NKMOF-1-M exhibit better low-pressure uptake than existing physisorbents and possesses the highest selectivities yet reported for C H /CO and C H /CH . The performance of NKMOF-1-M is not driven by the same mechanism as current benchmark physisorbents that rely on pore walls lined by inorganic anions.

Adsorptive Separation of Acetylene from Ethylene in Isostructural Gallate‐Based Metal–Organic Frameworks

“…As shown in Figure a–c, all M‐gallates exhibited perpendicular C 2 H 2 uptake (80.4, 98.4, 87.1 cm 3 g −1 for Ni‐, Mg‐, Co‐gallate, respectively) at 298 K and 1.0 bar. The capacities of C 2 H 2 at 298 K and 1.0 bar of M‐gallate, for example, Ni‐gallate (80.4 cm 3 g −1 ), compared with UTSA‐200 (81.9 cm 3 g −1 ), SIFSIX‐2‐Cu‐i (90.0 cm 3 g −1 ), M′MOF‐3 (42.6 cm 3 g −1 ), UTSA‐100 (88.6 cm 3 g −1 ), NKMOF‐1‐Ni (61.0 cm 3 g −1 ), and NKMOF‐1‐Cu (51.0 cm 3 g −1 ) showed an excellent capacity and predictable selective capturing of C 2 H 2 over C 2 H 4 . After careful comparison, it could be found that the slight enlargement of the pore sizes (≈0.3 Å) from Co‐gallate to Ni‐gallate also enabled higher C 2 H 2 uptakes at low pressure within 0.05 bar (Figure d), that is, 59.6 cm 3 g −1 , 70.6 cm 3 g −1 , and 69.9 cm 3 g −1 for Ni‐, Mg‐, and Co‐gallate materials, respectively.…”

Ultramicroporous Building Units as a Path to Bi‐microporous Metal–Organic Frameworks with High Acetylene Storage and Separation Performance

“…[8f] However the OMS affinity for both C 2 H 2 and CO 2 is not helpful for C 2 H 2 /CO 2 selectivity.H igh C 2 H 2 /CO 2 -selective MOFs include those with anionic groups such as MF 6 2À (M = Si, Ti,a nd so on) created by Eddaoudi, [2] Zaworotko, [9a] and Chen [9b] because of their strong interactions (such as CH···F) with C 2 H 2 .B ut compared with the best C 2 H 2 -storage MOFs, their uptake capacity is relatively low. [10] Also,t he tailored ultramicropore can endow MOFs with as ieving effect, leading to highly selective adsorption of C 2 H 2 over CO 2 . [11] However,s uch materials usually exhibit much lower C 2 H 2 adsorption capacity owing to low surface area.…”

Robust Microporous Metal–Organic Frameworks for Highly Efficient and Simultaneous Removal of Propyne and Propadiene from Propylene

“…However, the use of traditional porous materials,s uch as zeolites, [5,6] and activated carbon [7] to separate ternary propyne/propadiene/ propylene gas mixtures has not been realized yet, possibly because of the similar physical properties,s tructure,a nd molecular sizes of propyne,p ropadiene,a nd propylene (Scheme 1). [9][10][11][12][13] Much effort has been devoted to the use of MOFs for the separation of binary gas mixtures, such as acetylene/ethylene, [14][15][16][17][18][19] ethylene/ethane, [14,[20][21][22] carbon dioxide/methane, [23,24] carbon dioxide/nitrogen, [25,26] acetylene/carbon dioxide, [27,28] krypton/xenon, [29] propyne/ propylene, [30,31] and propylene/propane. monotonous structure,l ack of specific binding sites) owing to their welldefined structure,f ine-tunable pore size,a nd customdesigned functional groups.…”

“…[19] NKMOF-1-M exhibits at hree-dimensional (3D) framework constructed by four-connected [M(pdt) 2 ] À building blocks (Figure 1). [19] NKMOF-1-M exhibits at hree-dimensional (3D) framework constructed by four-connected [M(pdt) 2 ] À building blocks (Figure 1).…”

“…[19] NKMOF-1-M exhibits at hree-dimensional (3D) framework constructed by four-connected [M(pdt) 2 ] À building blocks (Figure 1). [19] Notably, NKMOF-1-M (M = Ni or Cu) can still retain its porosity and crystallinity after soaking in water for more than 1year at room temperature,a sverified by powder X-ray diffractometry (PXRD) and BET surface-area measurements (see Figures S1-S3 in the Supporting Information). Interestingly,c onjugated pyrazines and metal centers (Cu or Ni)l ocated on the wall of the 1D channels can provide two distinct binding sites for gas molecules (Figure 1), which could be beneficial for gas capture or separation applications.…”