Structural Diversity and Selective CO₂ Adsorption of Metal– Organic Frameworks Built with a Flexible Dipyridyl Ligand and Different Carboxylates

Abstract

A flexible dipyridyl ligand 1,2‐bis(4‐pyridylmethylamino)ethane (L) was synthesized and its diverse coordination mode with Zn(II) and Cd(II) in presence of different dicarboxylate renders five novel Metal–Organic Frameworks, namely, {[Zn(L)(BDC)]⋅6.5H2O}n (1), {[Zn(L)(NH2‐BDC)]⋅6.5H2O}n (2), {[Cd(L)(NH2‐BDC)]⋅7H2O}n (3), {[Cd(L)(OH‐BDC)]⋅H2O}n (4), and {[Cd(L)(diOH‐BDC)]⋅2H2O}n (5) (where, L= 1,2‐bis(4‐pyridylmethylamino)ethane and BDC=benzene‐1,4‐dicatboxylic acid). Crystal structural analysis reveals that compound 1 and 2 are 3D porous networks with open channels while compounds 3–5 are 2D MOFs. Complex 3 contains hydrogen bonded water molecules in between the 2D layers while 4 and 5 are highly dense compounds. The ligand L adopts different conformations which directed the final topology in these complexes. Complex 1–2 have a rare topology, gra, while 3–5 have four connected uninodal net with sql topology. The solvent accessible void volume for 1–3 comes out to be 51.2%, 52.3%, and 27% respectively. The gas adsorption studies reveal that 1–3 exhibit permanent porosity having type I isotherm and selectively adsorb CO2 gas over nitrogen and methane at low temperature with final uptake of 24.18 cc, 22.35 cc and 14.64 cc g−1 at STP, respectively. Vapour sorption study reveals that all the complexes selectively adsorb water vapour than methanol or ethanol vapours with final amount reached to 182.44 cc, 219.29 cc, 189.21 cc, 81.79 cc and 66.48 cc g−1 at room temperature. Solid‐state photoluminescence studies have been performed for all the complexes at room temperature (RT) and emission maximum for each complex are red shifted.

Deciphering the Weak CO2···Framework Interactions in Microporous MOFs Functionalized with Strong Adsorption Sites—A Ubiquitous Observation

“…In recent years, several classes of porous materials have been explored for their CO 2 capture capacity, and metal organic framework compounds stand out. − Some of the major molecular-level features responsible for these high CO 2 capture capacities of the MOFs include bare-metal or open-coordination sites and basic functional groups such as amines, pyridyls, or azoles. , Another feature which can be seen as a functionality on its own is the shape and size of the pores in the framework. Bare-metal sites interact with the oxygen of the CO 2 in a head-on mode.…”

High proton conductivity behavior in a 2D metal sulfite constructed from a histidine ligand

“…The reason is that the coordination between histidine and zinc ions effectively increases the rigidity of the ligand and reduces the energy loss through non-radiative thermal vibration. [58][59][60][61]…”

Design and synthesis of a turn-off fluorescent sensor based on a multifunctional Zn(ii) coordination polymer for the detection of Fe3+, Hg2+ and 4-nitrophenol

“…In the ligand, the deprotonated carboxyl groups can bond strongly with metal centers, facilitating the construction of CP materials. [25][26][27] Meanwhile, according to the principle of soft and hard acids and bases in coordination chemistry, the alkynyl functional group easily interacts with soft acid metal ions such as Hg 2+ , which makes such ligands attractive as luminescent sensors. [28][29][30][31] In combination with d 10 transition metals (e.g.…”