Pillar Modularity in fsc Topology Hybrid Ultramicroporous Materials Based upon Tetra(4-pyridyl)benzene

Abstract

Hybrid ultramicroporous materials (HUMs) are porous coordination networks composed of combinations of organic and inorganic linker ligands with a pore diameter of <7 Å. Despite their benchmark gas sorption selectivity for several industrially relevant gas separations and their inherent modularity, the structural and compositional diversity of HUMs remains underexplored. In this contribution, we report a family of six HUMs ( SIFSIX-22-Zn , TIFSIX-6-Zn , SNFSIX-2-Zn , GEFSIX-4-Zn , ZRFSIX-3-Zn , and TAFSEVEN-1-Zn ) based on Zn metal centers and the tetratopic N-donor organic ligand tetra(4-pyridyl)benzene ( tepb ). The incorporation of fluorinated inorganic pillars (SiF 6 2– , TiF 6 2– , SnF 6 2– , GeF 6 2– , ZrF 6 2– , and TaF 7 2– , respectively) resulted in (4,6)-connected fsc topology as verified using single-crystal X-ray diffraction. Pure-component gas sorption studies with N 2 , CO 2 , C 2 H 2 , C 2 H 4 , and C 2 H 6 revealed that the large voids and narrow pore windows common to all six HUMs can be leveraged to afford high C 2 H 2 uptakes while retaining high ideal adsorbed solution theory (IAST) selectivities for industrially relevant gas mixtures: >10 for 1:99 C 2 H 2 /C 2 H 4 and >5 for 1:1 C 2 H 2 /CO 2 . The approach taken, systematic variation of pillars with retention of structure, enables differences in selectivity to be attributed directly to the choice of the inorganic pillar. This study introduces fsc topology HUMs as a modular platform that is amenable to fine-tuning of structure and properties.

Does the Central Nitrogen Atom Make a Difference? A Comparison of Non‐Coordinating Pyridine and Benzene Spacers in Multitopic Ligands

“…[123] Zaworotko and coworkers demonstrated selectivity in gas uptake as a function of the choice of the inorganic pillar in members of the above zinc(II)-containing series; high C 2 H 2 uptakes were reported. [122] The effective separation of C 2 À C 3 alkyne/alkene mixtures has been confirmed using the pillared network [Cu 3 (58) 4 (SiF 6 ) 3 ] n which comprises interconnected 2D-{Cu(58)} n 2n + sheets containing the tritopic ligand 58 (see Scheme 17). [124]…”

“…[Fe( 45 ){Pt(CN) 4 }] n crystallizes with guest molecules of 45 in the cavities, and solvent guests may be reversibly varied; these materials exhibit spin‐crossover behavior [119] . Structurally related pillared materials include [Zn( 45 )(SiF 6 )] n , [120,121] [Zn( 45 )(GeF 6 )] n , [Zn( 45 )(SnF 6 )] n , [Zn( 45 )(TiF 6 )] n , [Zn( 45 )(TaF 7 )] n , and [Zn( 45 )(ZrF 6 )] n , [122] in addition to [Fe( 45 ){Au(CN) 2 }] n n + with linear Au(I), and [Fe( 45 ){Au(CN) 2 X 2 }] n n + (X=Br, I) with square‐planar Au(III) [123] . Zaworotko and coworkers demonstrated selectivity in gas uptake as a function of the choice of the inorganic pillar in members of the above zinc(II)‐containing series; high C 2 H 2 uptakes were reported [122] .…”

Dinuclear Copper Sulfate-Based Square Lattice Topology Network with High Alkyne Selectivity

“…HUMs are exemplified by hexafluorosilicate (SIFSIX) PCNs such as the microporous PCNs SIFSIX-1-Zn and SIFSIX-1-Cu (1 = 4,4′-bipyridine), reported in 1995 and 2000, respectively. HUMs have since been expanded to include a range of fluorinated inorganic anions , comprising metal centers such as Ti, , Nb, Ge, Zr, Al, and Ta . Such sorbents are of particular note because they can exhibit exceptional trace gas separation properties. , Unfortunately, the use of fluoride-based anions can be a cause for concern due to the risk of HF exposure during inorganic anion synthesis, or upon thermal decomposition of the PCN, or otherwise pose health and environmental risks due to the use of toxic heavy metal ions.…”

Enhanced CO2 sorption properties in a polarizable [WO2F4]2−-pillared physisorbent under direct air capture conditions

“…17 Herein, we probe the properties of a hybrid ultramicroporous material that is pillared by a WO 2 F 4 2À anion. Most hybrid ultramicroporous materials studied to date have consisted of hexafluoro anions (O h , e.g., SiF 6 , TiF 6 , SnF 6 , 18,19 and GeF 6 ), 20 pentafluoro (D 3h , e.g. AlF 5 , FeF 5 ), 21,22 or oxyfluoro-anions (C 4v , e.g.…”

“…Most hybrid ultramicroporous materials studied to date have consisted of hexafluoro anions ( O h , e.g. , SiF 6 , TiF 6 , SnF 6 , 18,19 and GeF 6 ), 20 pentafluoro ( D 3h , e.g. AlF 5 , FeF 5 ), 21,22 or oxyfluoro-anions ( C 4v , e.g.…”