Sorting of C₄Olefins with Interpenetrated Hybrid Ultramicroporous Materials by Combining Molecular Recognition and Size‐Sieving

Abstract

C 4 olefin separations present one of the great challenges in hydrocarbon purifications owing to their similar structures,t hus as ingle separation mechanism often met with limited success.H erein we report as eries of anion-pillared interpenetrated copper coordination for whicht he cavity and functional site disposition can be varied in 0.2 scale increments by altering the anion pillars and organic linkers (GeFSIX-2-Cu-i (ZU-32), NbFSIX-2-Cu-i (ZU-52), GeFSIX-14-Cu-i (ZU-33)), whichenable selective recognition of different C 4 olefins.I nt hese materials the rotation of the organic linkers is controlled to create acontracted flexible pore window that enables the size-exclusion of specific C 4 olefins, while still adsorbing significant amounts of 1,3-butadiene (C 4 H 6 )o r1 -butene (n-C 4 H 8 ). Combining the molecular recognition and size-sieving effect, these materials unexpectedly realized the sieving of C 4 H 6 /n-C 4 H 8 ,C 4 H 6 /iso-C 4 H 8 ,a nd n-C 4 H 8 /iso-C 4 H 8 with high capacity.C 4 olefins including 1,3-butadiene (C 4 H 6 ), 1-butene (n-C 4 H 8 ), and isobutene (iso-C 4 H 8 )a re basic organic raw materials for the production of avariety of synthetic rubbers and chemicals.[1] C 4 olefins are mainly produced from the C 4 fraction of cracking gases of petroleum and the high-purity of each C 4 olefin is desired for its downstream processes. [2] However,t hese C 4 olefins have similar molecular shapes and physical properties,s uch as close boiling points and polarizability (Scheme S1 and Table S1 in the Supporting Information). Currently,i ndustrial separation of C 4 H 6 , n-C 4 H 8 ,a nd iso-C 4 H 8 is performed by extractive distillations and cryogenic distillations, [3] which are highly energy-intensive and environmentally unfriendly processes.Physisorption using porous materials [4] is ap romising energy-saving technology for hydrocarbon separations. [5] Many attempts have been made to investigate the potential of porous materials such as zeolites, [2b, 6] metal-organic frameworks (MOFs) and/or porous coordination polymers (PCPs), [1b,2a, 7] for C 4 separations through the favorable enthalpic interaction, [7c] kinetic separation, [2b] controlling gas conformation, [1b] and guest-responsive mechanism. [2a, 7d-f] MOFs functionalized by open metal sites and hydrophobic surface exhibited high uptake of C 4 olefins, [7b,c] thanks to their strong binding energies;h owever they generally have low or even negligible selectivity owing to the highly structural similarity of C 4 isomers.U ltramicroporous materials that exhibit the size-exclusive sieving effect can reach high selectivity for C 4 H 6 /n-C 4 H 8 ,b ut have low uptake of C 4 H 6 (ca. 0.83 mmol g À1 on all-silica dica-dodecasil 3R (DD3R) at 303 Ka nd 1bar). [2d] Additionally,m olecular sieving is really hard to achieve,a st hat requires precise control on pore aperture size.V ery few zeolites have demonstrated sizeexclusive sieving effect for partial C 4 isomers. [2d, 6a] Clearly, individual strong binding or molecular sieving mecha...

Highly efficient separation of linear and branched C4 isomers with a tailor‐made metal–organic framework

“…In particular, it is highly desirable to design advanced porous materials with hyperfine‐tuned pore aperture dimensions that can block branched isomers from normal paraffins and/or olefins. With respect to the separation of molecules with different sizes and/or length, MOFs containing cages interconnected via small windows or size were shown to possess interesting properties leading to remarkable separation efficiencies 32‐38 . Such a conceivable selective molecular exclusion in MOFs would be ideal for gas/vapor separation of isomers with similar physical–chemical properties.…”

High Yield, Low-Waste Synthesis of a Family of Pyridyl and Imidazolyl-Substituted Schiff Base Linker Ligands

“…The modularity of SIFSIX-1-Zn enables facile linker ligand and/or metal substitution and can offer exquisite control over pore size, especially in the ultramicropore (<0.7 nm) range, and pore chemistry. Tight fitting pores and strong electrostatics have enabled HUMs to set new performance benchmarks for challenging trace separations such as CO 2 /N 2 , C 2 H 2 /C 2 H 4 , − C 2 H 2 /CO 2 , , Xe/Kr, , C 3 H 6 /C 3 H 8 , C 4 H 6 / n -C 4 H 8 / iso -C 4 H 8 , H 2 O/CH 4 and SO 2 /CO 2 . In this context, we have recently shown how HUMs with closely related organic linkers can exhibit significant differences in their structures and properties. ,, Such linker ligands are also known to afford different network structures from the same molecular building blocks, i.e., supramolecular isomers. , Hence, there is motivation to investigate how subtle changes in the structure of a library of related organic linker ligands can influence coordination network structure and properties.…”

Recent Progress on Microfine Design of Metal–Organic Frameworks: Structure Regulation and Gas Sorption and Separation

“…(SiF 6 ) 2− and other related fluorinated pillar-based MOFs have generated a great interest recently and have shown potential for many applications, especially for gas sorption/separation. [58][59][60][61] The platform is based on a simple pcu net, where four nitrogen-based ligands (pyrazine, bipyridine, etc.) coordinate with transition metals (Zn, Cu, Ni, etc.)…”