Synthesis, structure and hydrogen sorption properties of a pyrazine-bridged copper(I) nitrate metal-organic framework

Abstract

A new copper(I) pyrazine-bridged coordination polymer [Cu2(pyz)3(NO3)2]·2DMF] (pyz = pyrazine) (1) has been synthesized and characterized by FT-IR, TG/DTG, DSC and single crystal X-ray diffraction techniques. The X-ray crystallographic result reveals a two-dimensional network structure containing hexagonal pores. Thermal analysis of compound 1 reveals it is stable to 380 °C, and gas sorption studies showed that it adsorbs 1.04 wt% hydrogen at 1 atm and 77 K. Compound 1 crystallizes in a triclinic system, space group P-1 (no. 2), a = 7.9550(2) Å, b = 7.9810(2) Å, c = 11.0660(3) Å, α = 76.328(1)°, β = 71.115(1)°, γ = 84.577(1)°, V = 645.79(3) Å3, Z = 2, T = 150(2) K, μ(MoKα) = 1.709 mm-1, Dcalc = 1.639 g/cm3, 11111 reflections measured (7° ≤ 2Θ ≤ 54.96°), 2951 unique (Rint = 0.0539) which were used in all calculations. The final R1 was 0.0346 (>2σ(I)) and wR2 was 0.0727 (all data).

Intrinsic Specific Activity Enhancement for Bifunctional Electrocatalytic Activity toward Oxygen and Hydrogen Evolution Reactions via Structural Modification of Nickel Organophosphonates

“…In addition, the FT-IR measurement results demonstrate that the presence of the characteristic bands corresponds to the functional groups and solvent molecules present in the title compounds (Figures S7). The observed absorption band in the region of 3650–3500 cm –1 corresponds to the stretching vibration of the hydroxyl group present in the form of free water and OH group attached to the diphosphonate ligand (H 4 hedp unit). − Besides, the peaks in the region of 3200–2800 cm –1 can be attributed to the stretching vibrations of C–H bonds present in the pyrazine ring and the methyl group of the phosphonate unit. − The peaks in the region from 1645 to 1420 cm –1 can be attributed to the symmetric and asymmetric modes of C–H and C–C bonds in both the compounds. − Notably, the sharp characteristic absorption peaks appeared in the region of 1550–1350 cm –1 correspond to the CN and CC stretching vibrations of the pyrazine moieties present in compound II, though such characteristic peaks are absent in the case of compound I , further confirming that no amine molecules are bound to the structure. − Substantially, the peaks in the region of 1150–1000 cm –1 in both the compounds can be assigned to the stretching vibrations of the C–O bond accompanied by the CPO 3 group of diphosphonate moieties; however, in the case of compound II , deformation of pyrazine ring can also be observed in the band of 800–600 cm –1 . − Additionally, the peaks present in the region of 750–400 cm –1 can be ascribed to the P–O, P–C, and Ni–O stretching modes in the compounds I and II . ,,− …”

“…In today’s scenario, dual-ligand approach has been taken into consideration for the synthesis of novel hybrid frameworks. − In general, metal phosphonates incorporated with different types of auxiliary ligands have given rise to distinct novel architectures of the hybrid frameworks. − Earlier, various N-containing aliphatic or aromatic ligands were utilized to form metal phosphonate hybrid structures. Such auxiliary ligands in hybrid framework structures can act as templates or structure-directing agents, and they can also coordinate with different metal centers to generate various molecular structures to 3D hybrid metal phosphonate frameworks. − ,− Among various N-containing auxiliary ligands, pyrazine-based metal phosphonate hybrid structures are very less explored until date. − The diverse alignment of the pyrazine ligand, which often binds with different metal centers, as well as the flexible coordination of phosphonate moieties not only provides new metal phosphonate architectures but also offers a versatile platform for designing active electrocatalysts to promote water-splitting reactions. However, it is evident that most of the metal phosphonate structures possess marginally less porosity compared to CPs and MOFs due to the incorporation of template agents within their pore channels. ,, Despite the low porosity of hybrid metal phosphonate frameworks, the specific role of the incorporated auxiliary ligands in metal phosphonate frameworks toward energy-related applications has not been examined so far, though a very few metal phosphonate structures have been introduced as efficient electrocatalysts for water-splitting technologies. ,,, …”