Multifaced Generation of MOF Coatings via Vapor-Phase Sublimation and Deposition Reactions

TL;DR

A new vapor-phase method is developed to create MOF coatings with controlled properties, showing good stability and cell compatibility.

Contribution

A general vapor sublimation and deposition method for MOF coatings with tunable morphology and properties is introduced.

Findings

MOF coatings with surface area of 1250 m²/g and thicknesses from 200 nm to 5 μm were successfully fabricated.

The coatings showed high adhesion (ASTM D3359 standard) and promoted cell viability and osteointegration.

The fabrication process allows pore size control, crystalline orientation customization, and cargo encapsulation.

Abstract

A general fabrication method for metal–organic
framework
(MOF) coatings through a vapor sublimation and deposition process
is reported. The vapor-phase fabrication mechanism relies on the interplay
between thermodynamic properties and the solid–vapor interface
reaction. The processing parameters of ion concentration, vapor pressure,
and system temperature enable control of the sublimation rate, and
ion–linker nucleation and coordination reactions occur at the
dynamic solid–vapor interface to form the proposed MOF coatings.
The reaction rate is controllable and is proportional to the sublimation
rate during the fabrication process. On the basis of the proposed
fabrication mechanism, experiments are facilitated to obtain combinations
of multiple metal cores and a variety of functionalized linkers for
vapor deposition from solid solution sublimation. The fabrication
process involves pore size control, crystalline orientation customization,
and encapsulation of cargo to form composite coatings, and these processes
are implemented during the same one coating fabrication process. The
initiation and manipulation of the nucleation radius and thus the
nucleation rate are easy to control and are related to the fabricated
MOF coatings with tunable crystalline morphologies. Moreover, the
MOF coating thickness is a time-dependent process that is proportional
to the sublimation rate and deposition time. In the present study,
the surface area of the fabricated MOF coatings was 1250 m2/g, the Young’s modulus was 2.8 GPa, the surface roughness
was 238.7 ± 17.3 nm, and thicknesses ranging from 200 nm to 5
μm were prepared. Maximized compatibility is also discussed
through the exploitation of solid solutions that are free of organic
solvents and a purely dry process, and the final MOF coatings are
conformal with high fidelity regardless of the substrate material
type and the complexity of the geometries in both 2D and 3D. The stability
of the MOF coating is inspected by an adhesion test that reveals the
highest adhesion standard in the ASTM D3359 classification. The cell
culture on this coating verified high cell viability with promoted
cell attachment, proliferation, and increased osteointegration activities.

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