Toward Ideal Metal–Organic Framework Thin-Film Growth via Automated Layer-by-Layer Deposition: Examples Based on Perylene Diimide Linkers

Abstract

Photoactive metal–organic framework (MOF) thin films offer an opportunity for translating the advantages of periodic, crystalline, and tailorable light-harvesting materials directly into devices such as those for photoelectrochemical solar energy conversion. In this study, we report the fabrication of light-absorbing perylene-diimide-containing pillared-paddlewheel MOF thin films using an automated layer-by-layer (LbL) deposition technique. Our focus here is on optimizing the growth of representative chromophoric MOFs as oriented films of uniform and predefined thickness. Growth was examined as a function of metal identity, pillaring ligand composition, and supporting-surface chemical functionality. Application of atomic force microscopy (AFM) and complementary techniques revealed that the surface-supported MOFs initially display island-type film growth (Volmer–Weber growth), resulting in comparatively rough films. Further growth is accompanied by the merging of islands, resulting in films that, depending on experimental details, can be remarkably smooth (i.e., roughness on the order of ±1 nm (one structural repeat unit in the pillaring direction)). These details include the use of 1,4-diazabicyclo[2.2.2]octane (DABCO) as a MOF pillar and ALD-grown zinc oxide as a film support (ALD = atomic layer deposition). Also helpful for mitigating island-type growth, at least in part, is the replacement of Zn2+ by Cu2+ as the metal component of the MOF. Notably, each of these adjustments entails replacing weaker chemical bonds with stronger ones.

Efficient and Rapid Synthesis of a Solvent and Ion-Responsive Luminescent Copper 2-Aminoterephthalate Thin Film

“…Furthermore, with the emergence of smart phone spectrometers, even simpler and cheaper designs could be envisioned in which qualitative Al detection could be realized simply using a smart phone and UV lamp. Moreover, the fabrication approach described here should be amenable to scale up and automated processes, , which should improve batch-to-batch consistency in film quality and properties.…”

Impact of Surface Functionalization and Deposition Method on Cu-BDC surMOF Formation, Morphology, Crystallinity, and Stability

“…SAMs with different functional groups can act as templates for oriented crystal growth by altering the anchoring ability of metal and organic linkers to the surface. This has been reported in the literature for other MOF materials deposited on MHDA and MUD SAMs. − The carboxyl-terminated functional groups for MHDA SAMs mimic the organic linker of the MOF coordinated equatorially to the copper paddle-wheel inorganic node, whereas hydroxyl-terminated groups for MUD SAMs imitate coordinated water molecules typically bound at the axial position of the copper paddle-wheel unit. This difference in the terminal functional group of the SAM alters how the copper dimers bind to the substrate and impact the crystal growth direction. , …”

“…For surMOF deposition by the LBL approach, substrates are functionalized with self-assembled monolayers (SAMs) such that the terminal surface functional groups anchor the surMOF film and can direct film morphology, crystallographic orientation, and roughness. − SurMOF films are LBL deposited by alternating immersion of these chemically modified substrates in solutions of the metal and organic components. Between metal and organic deposition steps, the substrates are rinsed by immersing in a solvent to remove excess unreacted starting materials on the surface.…”

Chemistry of Materials Nanoarchitectonics for Two-Dimensional Films: Langmuir–Blodgett, Layer-by-Layer Assembly, and Newcomers

“…Stupp and co-workers reported the preparation of columnar paddlewheel MOF films containing perylene diimide using an automated LbL deposition method. 119 The growth depends on the metal species, columnar ligand composition, and support surface chemistry. For example, island growth is suppressed by replacing Zn 2+ with Cu 2+ as the metal component.…”

“…With a metal-supplying precursor, this technique is expected to be a potential adversary for the preparation of high-quality LbL films for various MOFs. Stupp and co-workers reported the preparation of columnar paddlewheel MOF films containing perylene diimide using an automated LbL deposition method . The growth depends on the metal species, columnar ligand composition, and support surface chemistry.…”