Synthetic Routes for a 2D Semiconductive Copper Hexahydroxybenzene Metal–Organic Framework

Abstract

Conductive metal-organic frameworks (c-MOFs) have shown outstanding performance in energy storage and electrocatalysis. Varying the bridging metal species and the coordinating atom are versatile approaches to tune their intrinsic electronic properties in c-MOFs. Herein we report the first synthesis of the oxygen analog of M(CX) (X = NH, S) family using Cu(II) and hexahydroxybenzene (HHB), namely Cu-HHB [Cu(CO)], through a kinetically controlled approach with a competing coordination reagent. We also successfully demonstrate an economical synthetic approach using tetrahydroxyquinone as the starting material. Cu-HHB was found to have a partially eclipsed packing between adjacent 2D layers and a bandgap of approximately 1 eV. The addition of Cu-HHB to the family of synthetically realized M(CX) c-MOFs will enable greater understanding of the influence of the organic linkers and metals, and further broadens the range of applications for these materials.

A Dual‐Ligand Porous Coordination Polymer Chemiresistor with Modulated Conductivity and Porosity

“…Bao and co‐workers reported similar results, the presence of [Cu 3 (C 6 O 6 ) 2 (NH 3 CH 2 CH 2 NH 3 ) 1.36 ], in their study, in which they employed ethylenediamine as a copper‐chelating agent . Ethylenediamine could not be completely removed, even by treatment with hot water or Soxhlet extraction with methanol, possibly because it served as a counterion to neutralize the negatively charged CuO 4 (see Figures S10 and S11) . The corresponding EA results suggested a chemical formula of [Cu 3 (C 18 O 6 H 6 )(C 6 O 6 )(H 2 O) 11.78 (NH 3 CH 2 CH 2 NH 3 ) 1.59 ] for Cu 3 (HHTP)(THQ) (see Table S2).…”

“…We attributed the presence of N to the protonated ethylenediamine (NH 3 CH 2 CH 2 NH 3 2+ ) used in the reaction. Bao and co‐workers reported similar results, the presence of [Cu 3 (C 6 O 6 ) 2 (NH 3 CH 2 CH 2 NH 3 ) 1.36 ], in their study, in which they employed ethylenediamine as a copper‐chelating agent . Ethylenediamine could not be completely removed, even by treatment with hot water or Soxhlet extraction with methanol, possibly because it served as a counterion to neutralize the negatively charged CuO 4 (see Figures S10 and S11) .…”

“…The AB slipped‐parallel model with slightly slipped stacking of every two layers was energetically favored (see Figure S6). The broad (002) peak at 2 θ =14.68° (28.48° for λ =1.54178 Å) indicated short‐range ordering along the c ‐axis as compared with the narrow and sharp (100) peak at 2 θ =3.08° (5.95° for λ =1.54178 Å) of the ab plane, which is commonly observed for 2D π‐conjugated PCP/MOFs . The N 2 sorption isotherm at 77 K of Cu 3 (HHTP)(THQ) shows a BET surface area of approximately 441.2 m 2 g −1 (Figure d), thus revealing an intrinsically high porosity that cannot be achieved simply through a nonporous AB stacking structure with 60° rotations between neighboring layers or a significantly slipped parallel structure (see Figures S7 and S8).…”

“…0.97 nm) ligands in hexagonal Cu 3 (HHTP) 2 and tetrahydroxy‐1,4‐quinone (THQ, molecular size, ca. 0.55 nm) ligands in orthorhombic Cu 3 (THQ) 2 in one material led to a new dual‐ligand‐based 2D π‐conjugated EC‐MOF, Cu 3 (HHTP)(THQ) (Figure a). The uniform hybridization of the EC‐MOF based on two trigonal organic ligands (containing Cu complexes of two sizes) was expected to generate a unique trigonal crystal structure and ordered arrangement of redox‐active ligands on the nanoscale.…”

“…Simply increasing the concentration of THQ merely increases the amount of Cu 3 (THQ) 2 impurities. Therefore, ethylenediamine (en), which can strongly chelate to Cu 2+ and form the soluble coordination complex Cu(en) 2 , was chosen as the base to balance the coordination capability of HHTP and THQ with Cu 2+ through a competing bond‐formation mechanism during the preparation of the Cu 3 (HHTP)(THQ) dual‐ligand semiconductor (Figure ; see the Supporting Information for details). The failure to obtain Cu 3 (HHTP)(THQ) with monoamine bases also indicates the possible template role of ethylenediamine owing to the suitable length of the spacer in the molecule (see Figures S2 and S3).…”