Step-by-step growth of highly oriented and continuous seeding layers of [Cu2(ndc)2(dabco)] on bare oxide and nitride substrates

Abstract

The step-by-step growth of highly oriented and continuous thin films of [Cu 2 (ndc) 2 (dabco)] (1) at 50 C was studied and compared with growth directly from solvothermal mother solution at 120 C. The substrates were bare unmodified SiO 2 , Al 2 O 3 grown by atomic layer deposition (ALD), Ta 2 O 5 and Si 3 N 4 . The deposited layers of 1 were characterized via in-plane and out-of-plane X-ray powder diffraction (PXRD) and Scanning Electron Microscopy (SEM). The stepwise film formation process was studied by the variation of the reaction conditions and washing procedures indicating an island growth mode and the importance of storage effects. The highly oriented layers obtained by the step-bystep method were used as seeds for the deposition of thicker films of 500-700 nm with the same orientation directly from solvothermal mother solution.

Enantiopure Metal–Organic Framework Thin Films: Oriented SURMOF Growth and Enantioselective Adsorption

“…[6] Our test case, [{Zn 2 (cam) 2 (dabco)} n ] (+)-1 for (+)cam and (À)-1 for (À)cam) with an anisotropic tetragonal crystal system is such a layer-based MOF containing the binuclear "paddle wheel" zinc carboxylate unit {Zn 2 (COO) 4 N 2 } with distorted octahedral geometry, in which chiral camphorate bridge the dimeric zinc units into infinite planar layers {Zn 2 cam 2 } n . Linear N-donor ligands dabco occupy the axial Zn sites, perpendicularly to these {Zn 2 cam 2 } n layers, leading to a scaffold-like 3D structure.…”

“…The crystallite orientation of the samples can be controlled by applying self-assembled monolayer (SAM) modified QCM substrates with different functional head groups (pyridyl or carboxylate) and appropriate growth conditions. [6] As examined by surface X-ray diffraction in an out of plane mode (Figure 2), SURMOF (+)-1 was grown in (110) and (001) orientation on SAMs of MHDA and PPMT (MHDA = 16-mercaptohexadecanoic acid; PPMT = (4,(4-pyridyl)phenyl)methanethiol)) on Au-coated QCM substrates. The (110) and (001) X-ray diffraction (XRD) peak positions are very close to each other at 9.288 and 9.228 which is in accord with the corresponding single-crystal X-ray diffraction data.…”

“…Typically, the enantiopure SURMOFs (+)-1 or (À)-1 are grown (20-40 cycles) by dipping the QCM substrate alternately in ethanol solutions of Zn(Ac) 2 ·H 2 O and equimolar (AE)cam/dabco mixtures, each step followed by immediately rinsing with pure ethanol, according to the procedure developed in our group (Figure 1). [6] The growth process was monitored in situ by QCM as shown in Figure S1 in the Supporting Information. The crystallite orientation of the samples can be controlled by applying self-assembled monolayer (SAM) modified QCM substrates with different functional head groups (pyridyl or carboxylate) and appropriate growth conditions.…”

“…[5] LPE is also well suited for deposition of MOF (hetero-)structures, [6] for suppressing interpenetration, [7] and for tailoring the chemical functionality of the external SURMOF surface, [8] tasks which are quite difficult to achieve for MOF thin films grown by other deposition techniques. In particular SURMOFs of HKUST-1 allow the monitoring of adsorption/desorption of guest molecules at ultra thin and very homogeneous coatings and allow the determination of the corresponding diffusion constants.…”

“…[3][4][5][6][7][8][9] Once exposed to Zn(Ac) 2 ·H 2 O, carboxylate groups on the MHDA SAM will fix the paddle-wheel structured zinc dimer on the surface by replacing acetate groups from equatorial plane, which regulates SURMOF growth in the (110) orientation. Subsequent deposition of a mixture of (+)cam/dabco leads to occupation of axial sites by dabco and equatorial plane sites by (+)cam.…”