Electron Beam-Induced Surface Activation of Metal–Organic Framework HKUST-1: Unraveling the Underlying Chemistry

Abstract

The local chemical activation of surfaceanchored metal−organic frameworks is a novel electron beam-based lithographic technique with a high potential for the fabrication of chemically and spatially well-defined nanostructures in the sub-10 nm regime. In this context, we have performed a detailed investigation of electron beaminduced surface activation (EBISA) on the surface-anchored layers of HKUST-1 and copper(II) oxalate with the subsequent autocatalytic growth (AG) of deposits from the precursors Fe(CO) 5 and Co(CO) 3 NO. We use reflection absorption infrared spectroscopy and measurements on electron-stimulated desorption to identify the chemical species that trigger decomposition of the precursors on the activated surfaces. EBISA on HKUST-1 works for Fe(CO) 5 but not for Co(CO) 3 NO and is therefore chemical selective. On the other hand, we demonstrate that copper(II) oxalate is not susceptible to EBISA for both precursors, ruling out that Cu nanoparticles are active sites for initiating AG. A detailed discussion and comparison of the experimental results for both substrates and precursors is supported by a review of the current state of knowledge regarding the electron-induced chemistry of the investigated materials and on the precursor reactivity. On the basis of this analysis, we discuss specific species that are likely to trigger AG following EBISA of HKUST-1.

Probing the dynamics of Cu nanoparticle growth inside metal-organic frameworks upon electron beam irradiation

“…This observation is confirmed by the fact that measured interplanar distances (<dhkl> = 0.207 ± 0.004 nm) are in excellent agreement with the (111) interplanar distance of Cu (d111 = 0.2087 nm). Based on the previous results on the effect of e-beam on the chemi cal bounding of MOFs [15][16][17][18] and similar reason for growth of Pt and Au NPs from organometallic precursors [30,31], the possibility of the growth of the NPs from the constituent parts of HKUST-1 is due to breaking of bonds between copper and organic part. Moreover, the growth of pure Cu NPs instead of its oxide form is explained by a lower oxidation potential of Cu and relatively weak Cu COO bond energy, which promote the metallic state [15].…”

“…HKUST-1 is also a representative class of MOFs that are easy to grow on different surfaces following a layer-by-layer approach [26], which makes it promising for applied research. Moreover, the compound has been recently investigated to reveal the mechanism of electron-induced decomposition and the reason for NPs formation [15][16][17][18].…”

“…On the one hand, the compatibility of MOFs with chemical vapour deposition technology [9], plasma synthesis [10], and thin film growth [11] supports their integration into microelectronic devices. On the other hand, the post-processing of MOFs by heat [12], light [13,14] and electron irradiation [15][16][17][18] highlights their application as optical glasses and active optical elements in nanophotonics. Indeed, such post-processing initiates the deformation of framework backbone and breaking of chemical bonds [19] leading to formation of amorphous glassy compounds [12], nanocomposites [20] and nanoparticles (NPs) with different optial properties [13,14,21].…”

Exploring the fabrication and transfer mechanism of metallic nanostructures on carbon nanomembranes via focused electron beam induced processing

“…Of course, for EBISA a suitable combination of substrate and precursor is a prerequisite, that is, the substrate must be chemically altered by the electron beam and the precursor molecule must be susceptible to the altered site. Substrates that are known to fulfill the prerequisite are silicon oxide [ 10 , 12 ], rutile TiO 2 (110) [ 13 ], thin layers of porphyrin molecules [ 14 – 15 ], and surface-anchored metal-organic frameworks (SURMOFs) [ 16 – 17 ]. For oxide surfaces it is known that the activation mechanism is based on reactive oxygen vacancies, which are locally created by electron-stimulated oxygen desorption [ 18 – 19 ].…”

Additive Nano-Lithography with Focused Soft X-rays: Basics, Challenges, and Opportunities

“…Several recent studies have demonstrated that focused electron beam induced processing (FEBIP) has high potential for the controlled bottom-up fabrication of metallic 3D nanostructures [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. Furthermore, the basic processes during FEBIP are understood to more and more detail leading to developments towards more diverse, cleaner and more defined deposits for various potential applications [7,[15][16][17][18]. The method employs a focused electron beam to induce local dissociation of surface-absorbed metal organic precursor molecules supplied from the gas-phase.…”