Gas-phase loading of [Zn4O(btb)2] (MOF-177) with organometallic CVD-precursors: inclusion compounds of the type [LnM]a@MOF-177 and the formation of Cu and Pd nanoparticles inside MOF-177

Abstract

The highly porous and desolvated (activated) coordination polymer [Zn₄O(btb)₂] (btb = benzene-1,3,5-tribenzoate; MOF-177) was loaded with the organometallic compounds [Cp₂Fe], [Cp*₂Zn], [Cu(OCHMeCH₂NMe₂)₂], [CpCuL] (L = PMe₃, CNtBu) and [CpPd(η³-C₃H₅)] via solvent-free adsorption from the gas-phase. The inclusion compounds of the type [L_nM]_a@MOF-177, where [L_nM] indicates the respective compound and the parameter a denotes the number of molecules per formula unit of the MOF-177, were characterised by elemental analysis, FT-IR, solid-state NMR spectroscopy and by powder X-ray diffraction (PXRD). Remarkably high effective loadings of up to 11 molecules [Cp₂Fe] and 10 molecules [CpPd(η³-C₃H₅)] per cavity were determined. The analytical data prove that the host lattice and the guest molecules interact only by weak van-der-Waals forces without any significant change of the framework or the chemical nature of the included molecules. Cu nanoparticles showing the typical surface plasmon resonance at 580 nm and Pd nanoparticles of about 2.6 nm in size were formed inside the cavities of MOF-177 by the thermally activated hydrogenolysis of the inclusion compounds [CpCuCNtBu]₂@MOF-177 and by photolysis of [CpPd(η³-C₃H₅)]₁₀@MOF-177 in an inert atmosphere (Ar). PXRD, FT-IR and NMR studies revealed that the MOF-177 matrix remained unchanged during the decomposition process of the precursors. N₂ adsorption studies of the obtained materials Cu@MOF-177 (e.g. 10.6 wt.% Cu, 2309 m² g⁻¹) and Pd@MOF-177 (e.g. 32.5 wt.%, 1063 m² g⁻¹) reveal high remaining specific surface areas (Langmuir model).