Simultaneous interlayer and intralayer space control in two-dimensional metal−organic frameworks for acetylene/ethylene separation

Abstract

Three-dimensional metal−organic frameworks (MOFs) are cutting-edge materials in the adsorptive removal of trace gases due to the availability of abundant pores with specific chemistry. However, the development of ideal adsorbents combining high adsorption capacity with high selectivity and stability remains challenging. Here we demonstrate a strategy to design adsorbents that utilizes the tunability of interlayer and intralayer space of two-dimensional fluorinated MOFs for capturing acetylene from ethylene. Validated by X-ray diffraction and modeling, a systematic variation of linker atom oxidation state enables fine regulation of layer stacking pattern and linker conformation, which affords a strong interlayer trapping of molecules along with cooperative intralayer binding. The resultant robust materials (ZUL-100 and ZUL-200) exhibit benchmark capacity in the pressure range of 0.001–0.05 bar with high selectivity. Their efficiency in acetylene/ethylene separation is confirmed by breakthrough experiments, giving excellent ethylene productivities (121 mmol/g from 1/99 mixture, 99.9999%), even when cycled under moist conditions.

Breaking the trade-off between selectivity and adsorption capacity for gas separation

“…Eluted gaseous components were continuously monitored through GC analysis (see supplemental information for details, Figure S56). Figure 3 58,59 ; these values are consistent with the respective isotherm-based uptakes at 0. S1).…”

Benchmark Acetylene Binding Affinity and Separation through Induced Fit in a Flexible Hybrid Ultramicroporous Material

“…The observed interaction energy for C 2 H 2 exceeds previously reported materials as detailed in Figure 4 d and Table S4, for example, SIFIX‐3‐Ni ( Q st , 36.7 kJ mol −1 ), [26] SIFSIX‐2‐Cu‐i ( Q st , 52.7 kJ mol −1 ), [30] TIFSIX‐2‐Cu‐i ( Q st , 46.3 kJ mol −1 )[ 26 , 30 ] and UTSA‐300a ( Q st , 57.6 kJ mol −1 ), [20e] Ni 3 (pzdc) 2 (7Hade) 2 ( Q st , 44.5 kJ mol −1 ), [23] Fe(pyz)Ni(CN) 4 ( Q st , 32.8 kJ mol −1 ), [31] Co(pyz)Ni(CN) 4 ( Q st , 45–65 kJ mol −1 ), [32] ZUL‐100 Q st , 65.3 kJ mol −1 ) and ZUL‐200 ( Q st , 57.6 kJ mol −1 ). [20b] Other approaches that focus upon chemisorption can exhibit higher energies such as the nano‐trap MOF ATC‐Cu, for which a Q st of 79.1 kJ mol −1 driven by coordination between two metal centres was reported. [33] To further verify the energy of C 2 H 2 sorption, we conducted in situ pressure gradient differential scanning calorimetry (PG‐DSC) measurements.…”

Benchmark Acetylene Binding Affinity and Separation through Induced Fit in a Flexible Hybrid Ultramicroporous Material

“…Conversely, C 2 H 4 , CH 4 , and CO 2 exhibits low affinity with Q st values of 38.4, 11, and 33.6 kJ mol −1 , respectively (Figures 4 c and S23). The observed interaction energy for C 2 H 2 exceeds previously reported materials as detailed in Figure 4 d and Table S4, for example, SIFIX‐3‐Ni ( Q st , 36.7 kJ mol −1 ), [26] SIFSIX‐2‐Cu‐i ( Q st , 52.7 kJ mol −1 ), [30] TIFSIX‐2‐Cu‐i ( Q st , 46.3 kJ mol −1 ) [26, 30] and UTSA‐300a ( Q st , 57.6 kJ mol −1 ), [20e] Ni 3 (pzdc) 2 (7Hade) 2 ( Q st , 44.5 kJ mol −1 ), [23] Fe(pyz)Ni(CN) 4 ( Q st , 32.8 kJ mol −1 ), [31] Co(pyz)Ni(CN) 4 ( Q st , 45–65 kJ mol −1 ), [32] ZUL‐100 Q st , 65.3 kJ mol −1 ) and ZUL‐200 ( Q st , 57.6 kJ mol −1 ) [20b] . Other approaches that focus upon chemisorption can exhibit higher energies such as the nano‐trap MOF ATC‐Cu, for which a Q st of 79.1 kJ mol −1 driven by coordination between two metal centres was reported [33] .…”