Two Isostructural URJC-4 Materials: From Hydrogen Physisorption to Heterogeneous Reductive Amination through Hydrogen Molecule Activation at Low Pressure

Herein, two novel isostructural metal-organic frameworks (MOFs) M-URJC-4 (M = Co, Ni; URJC = "Universidad Rey Juan Carlos") with open metal sites, permanent microposity, and large surface areas and pore volumes have been developed. These novel MOFs, with polyhedral morphology, crystallize in the monoclinic P2₁/c space group, exhibiting a three-dimensional structure with microporous channels along the c axis. Initially, they were fully characterized and tested in hydrogen (H₂) adsorption at different conditions of temperature and pressure. The physisorption capacities of both materials surpassed the gravimetric H₂ uptake shown by most MOF materials under the same conditions. On the basis of the outstanding adsorption properties, the Ni-URJC-4 material was used as a catalyst in a one-pot reductive amination reaction using various carbonyl compounds and primary amines. A possible chemical pathway to obtain secondary amines was proposed via imine formation, and remarkable performances were accomplished. This work evidences the dual ability of M-URJC-4 materials to be used as a H₂ adsorbent and a catalyst in reductive amination reactions, activating molecular H₂ at low pressures for the reduction of C═N double bonds and providing reference structural features for the design of new versatile heterogeneous materials for industrial application.

Crystal structures of dimethyl 5-iodo-iso-phthal-ate and dimethyl 5-ethynyl-iso-phthal-ate

In dimethyl 5-iodo-isophthalate, C10H9IO4, (I), the planes through the methyl carboxyl-ate moieties are tilted with respect to the benzene ring, whereas the mol-ecular framework of dimethyl 5-ethynylisophthalate, C12H10O4, (II), is perfectly planar. The crystal structure of (I) is stabilized by a three-dimensional supra-molecular network comprising C-H⋯O=C hydrogen bonds, as well as I⋯O=C inter-actions. In the crystal of (II), the mol-ecules are connected via C-Hethyn-yl⋯O=C hydrogen bonds to infinite strands. Moreover, π-π arene stacking inter-actions connect the mol-ecular chains into two-dimensional supra-molecular aggregates.

5,5′-(Ethyne-1,2-diyl)diisophthalic acid dimethyl sulfoxide tetrasolvate

In the title compound, C₁₈H₁₀O₈·4C₂H₆OS, the mid-point of the triple bond of the main mol­ecule is located on a special position, i.e. about an inversion center. The carboxyl groups are twisted slightly out of the planes of the aromatic rings to which they are attached, making dihedral angles of 24.89 (1) and 7.40 (2)°. The cystal packing features strong O—H⋯O hydrogen bonds, weaker C—H⋯O inter­actions and O⋯S contacts [3.0981 (11) Å] and displays channel-like voids extending along the a-axis direction which contain the dimethyl sulfoxide solvent mol­ecules.