Tuning interfacial interactions for bottom-up assembly of surface-anchored metal-organic frameworks to tailor film morphology and pattern surface features

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 carboxylterminated 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 carboxylterminated 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 theμCP method to produce chemically patterned SAMs that selectively direct surMOF assembly to produce high-quality surMOF film features.

Advanced Surfaces by Anchoring Thin Hydrogel Layers of Functional Polymers

Surface design and engineering is a critical tool to improve the interaction of materials with their surroundings. Immobilization of soft hydrogels is one of the attractive strategies to achieve surface modification. The goal of this review is to provide a comprehensive overview of the different strategies used for surface tethering of hydrogel layers via crosslinking immobilization of pre-fabricated functional polymers. In this strategy, crosslinkable polymers are first prepared via various polymerization techniques or post-functionalization of polymers. Afterwards, the crosslinkable polymers are attached or tethered on the surfaces of substrates using a variety of approaches including photo-crosslinking, click reactions, reversible linkages, etc. For each case, the principles of hydrogel tethering have been explained in detail with representative examples.Moreover, the potential applications of the as-modified substrates in specific cases have also been addressed and overviewed.

Hierarchical assemblies of molecular frameworks—MOF-on-MOF epitaxial heterostructures

Functional,porous metal-organic frameworks(MOFs)have attracted much attention as a very flexible class of crystalline,porous materials.For more advanced applications that exploit photophysical properties,the fabrication of hierarchical assemblies,including the creation of MOF/MOF heterointerfaces,is important.For the manufacturing of superstructures with length scales well beyond that of the MOF pore size,layer-by-layer(Ibl)methods are particularly attractive.These allow the isoreticular approach to be extended to superstructures with micrometer length scales,a range that is not accessible using conventional MOF design.The Ibl approach further substantially extends the compositional diversity in MOFs.At the same time,the favorable elastic properties of MOFs allow for heteroepitaxial growth,even in the case of lattice misfits as large as 20%.While the MOF-on-MOF approach to designing multicomponent superstructures with synergistic multifunctionality can also be realized with sophisticated solvothermal synthesis schemes,the Ibl(or liquid-phase epitaxy)approach carries substantial advantages,in particular when it comes to the integration of such MOF superstructures into optical or electronic devices.While the structure vertical to the substrate can be adjusted using the Ibl method,photolithographic methods can be used for lateral structuring.In this review,we will discuss the Ibl liquid-phase epitaxy approach to growing surface-anchored MOF thins films(SURMOFs)as well as other relevant one-pot synthesis methods for constructing such hierarchically designed structures and their emerging applications.