Selective Modification of Hierarchical Pores and Surfaces in Nanoporous Materials

Abstract

Tailor‐made ordered mesoporous materials bear great potential in numerous fields of application where large interfaces are required. However, the inherent surfacechemical properties of conventional materials, such as silica, carbon or organosilica, poses some limitations with respect to their application. Surface manipulation by functionalization with chemically more reactive groups is one way to improve materials for their desired purpose. Another approach is the design of high surface‐area composite materials. The surface manipulation, either by functionalization or by introducing guest species, can be performed selectively. This means that when several distinct, i.e. , hierarchical, types of surfaces or pore systems exist in a material, each of them may be chosen for manipulation. Several strategies can be identified to achieve this goal. Molecules or molecule assemblies can be utilized to temporarily protect pores or surfaces (soft protection), while manipulation occurs at the accessible sites. This approach is a recurring motive in this review and can also be applied to rigid template matrices (hard protection). Furthermore, the size of functionalization agents (size protection) and their reactivity/diffusion (kinetic protection) into the pores can also be utilized to achieve selectivity. In addition, challenges in the synthesis and characterization of selectively manipulated ordered mesoporous materials are discussed.

Functionalized Mesoporous Thin Films for Biotechnology

“…As summarized recently by Tiemann and Weinberger [ 77 ], when different hierarchical surfaces of mesoporous materials are present, each of them can be selectively functionalized for applications in, e.g., sensing, cancer cell targeting, or drug delivery. For example, pores and surfaces can be protected with temporary ligands, or the dimension, reactivity and diffusion properties of the functionalizing agents can be used to selectively modify the material.…”

Synthesis of Amphiphilic Silica with High Exposure of Surface Groups and Its Utilization in Efficient Removal of Organic Dyes from Aqueous Solution

“…Post-graft method is efficient to modulate the composition of the surface groups through the substitution of hydrophilic hydroxyl with hydrophobic organic group, but it could not increase the total amount of the surface groups. [20] In this manuscript, a novel amphiphilic silica nanosphere was designed with the introduction of two kinds of organic groups with different polarity on its surface through a onestep condensation route: one is 3-aminopropyl being used as the polar and hydrophilic active sites, and the other one is n-propyl being used as the weakly polar and lipophilic active sites. With the introduction of organic groups, the surface hydrophilic silanol increased obviously as an uncommon accompanying result, and then caused a dramatic increase of the total surface groups' amount.…”

Simultaneous Nanolocal Polymer and In Situ Readout Unit Placement in Mesoporous Separation Layers

“… 16 Selective functionalization of the inner or outer surface of mesoporous materials has been demonstrated by applying several approaches, for example, soft template protection, kinetic protection, or size protection as, for example, recently summarized in a review article of Tiemann and Weinberger. 17 Functionalization of the outer surface of mesoporous materials allows capping of the mesopores enabling gating/switching of ionic transport 18 or controlled release of guest molecules entrapped inside the mesopores, 19 for instance. Such porous architectures can result in Janus-type multilayer porous materials and membranes, and several studies have been published, showing side-selective transport or oil–water separation.…”