Hydrogen adsorption in azolium and metalated N-heterocyclic carbene containing MOFs

Abstract

Azolium and metalated N-heterocyclic carbene (NHC) functionalised metal-organic frameworks (MOFs) have been investigated as adsorbents and heterogenous catalysts. Here we describe the structures of two sets of 1D polymeric structures, {[M 2 (μ 2 -HCOO)(HL) 2 ](NO 3 )•xDMF} n (M = Zn, x = 1, 1; Cu, x = 1.75, 2) and {[M 3 (HL) 4 (H 2 O) 4 ](NO 3 ) 2 •xDMF} n (M = Co, x = 2.75, 3; Mg, x = 0, 4; Mn, x = 1.5, 5), prepared from reactions of 1,3-bis(3-carboxyphenyl)-1H-imidazol-3-ium bromide (H 3 LBr) with M(NO 3 ) 2 •xH 2 O (M = Zn, Cu, Co and Mg)and MnCl 2 •4H 2 O. These pack as porous and non-porous 3D materials, respectively. In the case of the known Zn(II) material 1, which we reveal to be porous, we also report metalation of the NHC precursor concomitant with framework synthesis to give {[Zn 2 (μ 2 -HCOO)(HL) 1.6 (L-Cu-Br) 0.4 ](NO 3 ) 0.6 •0.75DMF} n (1-Cu). Compounds 1, 2, and 1-Cu show H 2 adsorption enthalpies of −9.9, −9.1, and −9.7 kJ mol −1 respectively, and allow the effect of micropores decorated with charged imidazolium moieties, or NHC-CuBr entities, on H 2 adsorption to be probed.

Preparation and Post-Assembly Modification of Metallosupramolecular Assemblies from Poly(N-Heterocyclic Carbene) Ligands

“…When considering the cost of homogeneous organometallic complexes, as well as the environmental issues related to their separation and recovery in industrial processes, the heterogenization of homogeneous NHC-metal catalysts is also of great interest. , Metal–organic frameworks (MOFs), with defined structures and isolated catalytic sites, , have been employed as carriers for the heterogenization of NHC-metal catalysts. − In addition, a number of examples of coordination polymers with pendant poly-NHC units have been described. , …”

Size effects on rhodium nanoparticles related to hydrogen-storage capability

“…The principal findings from these measurements are as follows. (1) In the VB HAXPES spectra, the intensity of peak 1 (the occupied d-DOS) was higher for bulk Rh than for Rh NPs. This indicates that the unoccupied d-DOS of Rh NPs may be more than that of bulk Rh.…”

“…The study of materials enabling the efficient storage and safe transport of fuel gases, particularly hydrogen gas, has mainly focused on areas such as metal-organic frameworks, [1][2][3] carbon materials, 4,5 and hydrogen-storage alloys. [6][7][8] Hydrogen-storage alloys are metallic materials that have a unique ability to store hydrogen compactly and safely as a consequence of the stability of their hydrides.…”

Microporosity Enhancement in a One‐Dimensional Imidazolium Caged Metal‐Organic Framework by Highly Selective Postsynthetic Removal of Inner Yttrium Clusters

“…13 Sumby and coworkers reported five different onedimensional (1D) chained MOFs that consist of various metal ions (Mg, Mn, Co, Zn, and Cu) and a U-shaped imidazolium ligand. 14 Two distinct topologies were generated differing in the coordination geometry and coordination number of the metals: 1D porous undulating chains with a paddle-wheel cluster (Zn and Cu) and nonporous "polymeric caged" structures with a trimeric cluster (Mg, Mn, and Co).…”

“…Herein, we report a new caged 1D polymer MOF (YMOF-Y) of previously unknown topology composed of U-shaped imidazolium linkers and yttrium metal ions with a high coordination number (8 and 10). 14 Cavities in the original YMOF-Y are occupied by Y 4 metal clusters; however, a porous structure could be generated by the postsynthetic leaching out the clusters using alkali metal solutions. To the best of our knowledge, this is the first example of a selective metal cluster removal from a preformed MOF.…”