1 research outputs found
Screening Hofmann Compounds as CO<sub>2</sub> Sorbents: Nontraditional Synthetic Route to Over 40 Different Pore-Functionalized and Flexible Pillared Cyanonickelates
A simple reaction scheme based on
the heterogeneous intercalation
of pillaring ligands (HIPLs) provides a convenient method for systematically
tuning pore size, pore functionality, and network flexibility in an
extended series of pillared cyanonickelates (PICNICs), commonly referred
to as Hofmann compounds. The versatility of the approach is demonstrated
through the preparation of over 40 different PICNICs containing pillar
ligands ranging from ∼4 to ∼15 Å in length and
modified with a wide range of functional groups, including fluoro,
aldehyde, alkylamine, alkyl, aryl, trifluoromethyl, ester, nitro,
ether, and nonmetalated 4,4′-bipyrimidine. The HIPL method
involves reaction of a suspension of preformed polymeric sheets of
powdered anhydrous nickel cyanide with an appropriate pillar ligand
in refluxing organic solvent, resulting in the conversion of the planar
[Ni<sub>2</sub>(CN)<sub>4</sub>]<sub><i>n</i></sub> networks
into polycrystalline three-dimensional porous frameworks containing
the organic pillar ligand. Preliminary investigations indicate that
the HIPL reaction is also amenable to forming Co(L)Ni(CN)<sub>4</sub>, Fe(L)Ni(CN)<sub>4</sub>, and Fe(L)Pd(CN)<sub>4</sub> networks.
The materials show variable adsorption behavior for CO<sub>2</sub> depending on the pillar length and pillar functionalization. Several
compounds show structurally flexible behavior during the adsorption
and desorption of CO<sub>2</sub>. Interestingly, the newly discovered
flexible compounds include two flexible Fe(L)Ni(CN)<sub>4</sub> derivatives
that are structurally related to previously reported porous spin-crossover
compounds. The preparations of 20 pillar ligands based on ring-functionalized
4,4′-dipyridyls, 1,4-bis(4-pyridyl)benzenes, and <i>N</i>-(4-pyridyl)isonicotinamides are also described