Nickel(ii) and copper(i,ii)-based metal-organic frameworks incorporating an extended tris-pyrazolate linker

Abstract

Solvothermal reactions between the tritopic pyrazole-based ligand 1,3,5-tris((1H-pyrazol-4-yl)phenyl)benzene (H₃BTPP) and nickel(II) perchlorate or copper(II) nitrate afforded two new metal-organic frameworks, Ni₃(BTPP)₂·solvent (Ni-BTPP) and Cu^I₄Cu^II₂(OH)₂(BTPP)₂·solvent (Cu-BTPP). Powder diffraction structure determination methods were employed to determine the crystal and molecular structure of the copper(I,II) derivative: triangular [Cu₃N₆(μ₃-OH)] nodes are connected to six nearby ones by the pyrazolate ligands, thus constructing flat two-dimensional layers that stack to form slit-like one-dimensional channels. Thermogravimetric analyses highlighted both the thermal stability and the permanent porosity of these two materials. Porosity was confirmed by N₂ adsorption at 77 K, yielding Langmuir specific surface areas of 1923(3) m² g⁻¹ and 874(8) m² g⁻¹ for Ni-BTPP and Cu-BTPP, respectively. Additionally, Ni-BTPP adsorbed 1.73 mmol g⁻¹ (7.6 wt%) of CO₂ at the mild conditions of 298 K and 1 bar.