Tuning interfacial interactions for bottom-up assembly of surface-anchored metal-organic frameworks to tailor film morphology and pattern surface features: Nanoscience: Special Issue Dedicated to Professor Paul S. Weiss

Abstract

Surface-anchored metal-organic frameworks (surMOFs) integrate nanoporous supramolecular MOF materials directly into architectures for applications such as gas storage, chemical sensing, and energy storage. Layer-by-layer solution-phase deposition of the MOF-14 components (1,3,5-tris(4-carboxyphenyl)benzene and copper (II) dimers, respectively) produces a porous and conformal film on carboxyl-terminated self-assembled monolayers (SAMs). In this research, the formation of ultrathin (less than 25 nm) surMOF films on codeposited bicomponent SAMs and microcontact printed SAMs is investigated by atomic force microscopy, ellipsometry, infrared spectroscopy, and contact angle goniometry. SAMs composed of methyl-terminated alkanethiols assembled on gold substrates inhibit surMOF formation, whereas carboxyl-terminated alkanethiols promote MOF-14-based film growth. To tune the density of carboxyl groups that anchor the film, methyl- and carboxyl-terminated alkanethiols of varying concentrations are codeposited on gold. This systematic study demonstrates how surMOF film formation and morphology are impacted by these SAMs with mixed surface functionalities. Chemical patterning methods for SAMs, such as microcontact printing (μCP), commonly have mixed chemical functionalities within certain regions of the pattern. Insights gained regarding how mixed surface functionalities affect surMOF film formation are applied herein to optimize the μCP method to produce chemically patterned SAMs that selectively direct surMOF assembly to produce high-quality surMOF film features.