Negative electrostatic potentials in a Hofmann-type metal-organic framework for efficient acetylene separation

Abstract

Efficient adsorptive separation of acetylene (C2H2) from carbon dioxide (CO2) or ethylene (C2H4) is industrially important but challenging due to the identical dynamic diameter or the trace amount. Here we show an electrostatic potential compatible strategy in a nitroprusside-based Hofmann-type metal-organic framework, Cu(bpy)NP (NP = nitroprusside, bpy = 4,4’-bipyridine), for efficient C2H2 separation. The intruding cyanide and nitrosyl groups in undulating one-dimensional channels induce negative electrostatic potentials for preferential C2H2 recognition instead of open metal sites in traditional Hofmann-type MOFs. As a result, Cu(bpy)NP exhibits a 50/50 C2H2/CO2 selectivity of 47.2, outperforming most rigid MOFs. The dynamic breakthrough experiment demonstrates a 99.9% purity C2H4 productivity of 20.57 mmol g−1 from C2H2/C2H4 (1/99, v/v) gas-mixture. Meanwhile, C2H2 can also be captured and recognized from ternary C2H2/CO2/C2H4 (25/25/50, v/v/v) gas-mixture. Furthermore, computational studies and in-situ infrared spectroscopy reveal that the selective C2H2 binding arises from the compatible pore electro-environment generated by the electron-rich N and O atoms from nitroprusside anions.

An ultramicroporous multi-walled metal–organic framework for efficient C2H2/CO2 separation under humid conditions

“…2b and c). The adsorption capacity of C 2 H 2 at 298 K is lower that of several benchmark MOFs such as SNNU-45 (134.0 cm 3 g −1 ), 36 FJU-90 (180 cm 3 g −1 ), 37 and UTSA-74 (103.5 cm 3 g −1 ) 38 (Table S1†) but is comparable to that of other ultramicroporous MOFs, such as [Co 3 (μ 3 -OH)(tipa)(bpy) 1.5 ]·3DMF·6H 2 O (39.5 cm 3 g −1 ), 39 PCPs-asp (36.7 cm 3 g −1 ), 40 Cu(bpy)NP (50.7 cm 3 g −1 ), 41 and Cu I @UiO-66-(COOH) 2 (51.7 cm 3 g −1 ). 42 It is worth noting that the slope of the C 2 H 2 adsorption isotherm at low pressure is steeper than that of CO 2 , indicating stronger interactions for C 2 H 2 with the framework.…”

Topological Design of Unprecedented Metal‐Organic Frameworks Featuring Multiple Anion Functionalities and Hierarchical Porosity for Benchmark Acetylene Separation

“…Acetylene (C 2 H 2 ) capture from gas mixtures is of grand importance in industry. [1][2][3] As a critical fundamental raw material for the manufacture of various organic chemicals and polymers, C 2 H 2 is generally produced from the cracking of hydrocarbons or partial combustion of natural gas, in which carbon dioxide (CO 2 ) inevitably coexists as a contaminant and needs to be removed to produce C 2 H 2 in high purity. [4,5] However, the separation of C 2 H 2 and CO 2 molecules are challenging because both molecules possess linear configurations with subtle differences in molecular dimensions (3.3 × 3.3 × 5.7 Å 3 for C 2 H 2 and 3.2 × 3.3 × 5.4 Å 3 for CO 2 ) and close similarities in physical properties (Table S1), including dipole moments, boiling point, and polarity.…”

De‐Linker‐Enabled Exceptional Volumetric Acetylene Storage Capacity and Benchmark C2H2/C2H4and C2H2/CO2Separations in Metal–Organic Frameworks

“…Meanwhile, for 1/99 C 2 H 2 /C 2 H 4 mixtures, C 2 H 2 can be retained in the column over 1362 min g À 1 and 701 min g À 1 with a total gas flow rate of 2 mL min À 1 at 273 and 298 K for SNNU-98-Mn (Figures 3c and 3e). Notably, the breakthrough interval time values are superior to all MOF adsorbents up to now under the same conditions (Table S5), such as ZJU-280a [1b] (300 min g À 1 ), Cu(bpy)NP [31] (228 min g À 1 ), Ni-DCPTP [32] (203 min g À 1 ), and NCU-100a [33] (150 min g À 1 ) at 298 K. Since some MOFs were tested with a flow rate of 1.25 mL min À 1 , such as ZU-33 [34] (1570 min g À 1 ), UTSA-200a [35] (1500 min g À 1 ), and SIFSIX-2-Cu-i [24] (800 min g À 1 ) at 298 K, we performed the study under the same conditions, and the results show that C 2 H 2 can be retained in the column over 2325 min g À 1 and 862 min g À 1 with a total gas flow rate of 1.25 mL min À 1 at 273 and 298 K for SNNU-98-Mn (Figure 3f). Also, a high selectivity of 10.1 was obtained from the 1/99 C 2 H 2 /C 2 H 4 mixture breakthrough curves at 298 K with a total gas flow rate of 2 mL min À 1 .…”