Polymorphism and orientation control of copper-dicarboxylate metal–organic framework thin films through vapour- and liquid-phase growth

Precise control over the crystalline phase and crystallographic orientation within thin films of metal–organic frameworks (MOFs) is highly desirable. Here, we report a comparison of the liquid- and vapour-phase film deposition of two copper-dicarboxylate MOFs starting from an oriented metal hydroxide precursor. X-ray diffraction revealed that the vapour- or liquid-phase reaction of the linker with this precursor results in different crystalline phases, morphologies, and orientations. Pole figure analysis showed that solution-based growth of the MOFs follows the axial texture of the metal hydroxide precursor, resulting in heteroepitaxy. In contrast, the vapour-phase method results in non-epitaxial growth with uniplanar texture only.

Electronic Supplementary Material (ESI) for CrystEngComm.This journal is © The Royal Society of Chemistry 2024 integrating the reciprocal space maps in terms of the length of the scatting vector.The data treatment was performed using GIDVis software. 2anning electron microscopy (SEM) images were acquired using a Philips XL30 FEG SEM microscope operating at an accelerating voltage of 10 keV.Samples were cleaved and sputter-coated with 2 nm of Pt before inspection using a Quorum Q150 sputter coater.and SIWGUB, 7 respectively) onto Cu(OH)2 nanobelts, showcasing the (100) orientation with respect to the substrate and the nanobelts.Thus, in both cases, the pore channels lay perpendicular to the surface.Crystallographic axes correspond to the MOF structure only.

SI5. Results and Discussion
Figure S7.a) Geometry of a rotating GIXRD experiment with k0 and k as the wavevectors of the primary and the diffracted X-ray beam, respectively.The beams enclose an angle of  i and  f relative to the substrate surface.The resulting scattering vector q (q = k -k0) is separated in two in-plane components (qx, qy) and in an out-of-plane component (qz).The sample is rotated during the measurement around the surface normal, and a diffraction pattern is taken by integrating a certain range of φ rotation.b) Two detector images measured at different φ angles converted into reciprocal space.

Figure S1 .
Figure S1.Crystal structure of the Cu(OH)2 nanobelts with orthorhombic symmetry and lattice constants a = 2.947 Å, b = 10.593Å and c = 5.2564 Å 3 with the crystallographic a-axis along the long axes of the nanobelts.

Figure S2 .
Figure S2.Pole figures of Cu(OH)2 nanobelt substrates recorded at q = 1.19 Å -1 (a) for the 020 peak and at 2.52 Å -1 (b) for the 111 peak.(c) Stereographic projection of Cu(OH)2 crystals according to an axial texture: crystals with the crystallographic a-axis along the substrate surface (these directions are represented by full black circles); an in-plane mosaicity of 10° is considered.

Figure S3 .
Figure S3.Schematic illustrations of the liquid-(a) and vapour-phase (b) conversion procedures and reaction set-ups.The liquid-phase conversion was performed by immersing Si substrates coated with Cu(OH)2 nanobelts in a saturated ligand solution for 30 min.For the vapour-phase conversion Si substrates coated with Cu(OH)2 nanobelts are positioned approximately in the middle of a 100 mL Schlenk tube together with linker powder in an open glass boat at the opposite end.After evacuating under dynamic vacuum (~10 -2 mbar) for 20 min, the evacuated tube stopcock is closed and placed in a forced convection oven preheated at 200 ºC for 16 hours.Created with BioRender.com

Figure S5 .
Figure S5.Reciprocal space maps obtained from synchrotron GIXRD data for a) Cu-BDC crystalline film converted under liquid-phase conditions b) Cu-BDC crystalline film converted under vapour-phase conditions; c) Cu-CDC crystalline film converted under liquid-phase conditions; d) Cu-CDC crystalline film converted under vapour-phase conditions.

Figure S6 .
Figure S6.Crystalline structures of vapour converted (a, b) Cu-BDC and (c, d) Cu-CDC (ZUBKEO4 and SIWGUB, 7 respectively) onto Cu(OH)2 nanobelts, showcasing the (100) orientation with respect to the substrate and the nanobelts.Thus, in both cases, the pore channels lay perpendicular to the surface.Crystallographic axes correspond to the MOF structure only.

Table S1 .
Previously reported Cu-BDC and Cu-CDC crystalline structures, detailing lattice parameters and data from the CCDC database, Cambridge, UK.