Landscaping Covalent Organic Framework Nanomorphologies

Abstract

The practical utilization of covalent organic frameworks (COFs) with manipulation at the atomic and molecular scale often demands their assembly on the nano-, meso-, and macroscale with precise control. Consequently, synthetic approaches that establish the ability to control the nucleation and growth of COF crystallites and their self-assembly to desired COF nanomorphologies have drawn substantial attention from researchers. On the basis of the dimensionality of the COF morphologies, we can categorize them into zero- (0-D), one- (1-D), two- (2-D), and three-dimensional (3-D) nanomorphologies. In this perspective, we summarize the reported synthetic strategies that enable precise control of the COF nanomorphologies’ size, shape, and dimensionality and reveal the impact of the dimensionalities in their physicochemical properties and applications. The aim is to establish a synergistic optimization of the morphological dimensionality while keeping the micro- or mesoporosity, crystallinity, and chemical functionalities of the COFs in perspective. A detailed knowledge along the way should help us to enrich the performance of COFs in a variety of applications like catalysis, separation, sensing, drug delivery, energy storage, etc. We have discussed the interlinking between the COF nanomorphologies via the transmutation of the dimensionalities. Such dimensionality transmutation could lead to variation in their properties during the transition. Finally, the concept of constructing COF superstructures through the combination of two or more COF nanomorphologies has been explored, and it could bring up opportunities for developing next-generation innovative materials for multidisciplinary applications.

Metal–Organic Framework Accelerated One-Step Capture and Reduction of Palladium to Catalytically Active Nanoparticles

“…Herein, we report a rapid and facile approach for one-step, in situ growing uniform and clean Pd NPs from a complicated matrix (Scheme ), where metal–organic frameworks (MOFs) act not only as the supports but also as accelerators to the adsorption and reduction of Pd. MOFs, a class of crystalline porous materials, have been extensively explored as adsorbents and supports for various species ranging from gases, metals, to biomolecules. − Due to their large surface area and uniform pore space, MOFs provide inherent advantages to achieve high capacity and good spatial distribution of guest molecules, which thus can synergistically boost the performance in catalysis, sensing, and biomedical applications. − The emergence of frameworks with high chemical stability promotes the efficacy and expands the areas of application further. − In this work, the variable chemical microenvironments created by the inorganic–organic hybrid composition of MOFs were exploited to tune the metal–support interactions, thus establishing an integrated strategy for not only binding but also directly reducing the noble metal to functional nanoparticles. Assisted by sonic waves and alcoholic solvent, selective capture of Pd­(II) from a complicated matrix to directly afford Pd NPs in MOFs was achieved under a mild condition (25 °C, 5 min) without the use of extra reducing or capping agents.…”

Soft 2D Covalent Organic Framework with Compacted Honeycomb Topology

“…Two-dimensional covalent organic frameworks (COFs) as a class of unique organic porous polymers have attracted significant interests in materials chemistry because of their signature topological structures as well as their important applications in catalysis, optoelectronics, separation, adsorption, , and so on. − Significantly, the topological structures of 2D COFs represent highly ordered and predictable crystalline features because their skeleton topologies originate from the geometry of the linker units, which can be represented by a topological model in mathematics. − By utilizing the combination of linear, triangular, tetragonal, hexagonal, and other more complex linkers, the resulting 2D COF structures enable topological diversity including honeycomb (hcb), square (sql), kagome (kg m), hexagon (hxl), kagome-dual (kgd), and more. − In order to expand the complexity and diversity of topologic structures of 2D COFs, an efficient method is to eliminate the structural symmetry of linker units without changing their linking mode. , In general, 2D COFs need to be constructed with rigid linker units so as to maintain their highly ordered, predictable, porous, and periodic structure. It is noteworthy that flexible monomer-based COFs have been reported recently, which still retains all the structural and property characteristics that have been well-established in rigid monomer-based COFs ( R-COFs ). − By contrast with these well-studied R-COFs reported to date, truly soft COFs ( S-COFs ) will program the structural blueprint for the other half of COFs, possibly leading to the emergence of novel topological structures and unique properties, which will significantly boost the development of COF materials.…”

Weaving microscale wool ball-like hollow covalent organic polymers from nanorods for efficient adsorption and sensing

“…Covalent organic polymers (COPs) showcase extensive applications in the fields of adsorption, catalysis and sensing because of their outstanding merits, such as large surface area and easy tailor-made functionalization. 1,2 It is generally recognized that the function of COPs is dependent not only on their physicochemical properties but also on structural morphologies. 2,3 Thus, some reaction parameters have been optimized to synthesize COPs with various morphologies in nanoscale (e.g., sphere, rod and sheet).…”

“…1,2 It is generally recognized that the function of COPs is dependent not only on their physicochemical properties but also on structural morphologies. 2,3 Thus, some reaction parameters have been optimized to synthesize COPs with various morphologies in nanoscale (e.g., sphere, rod and sheet). 4 Recently, growing interest has focused on assembly of nanoscale materials to well-defined and highorder 3D microarchitectures owing to the new exotic functions from advanced architectures.…”

“…1,2 It is generally recognized that the function of COPs is dependent not only on their physicochemical properties but also on structural morphologies. 2,3 Thus, some reaction parameters have been optimized to synthesize COPs with various morphologies in nanoscale ( e.g. , sphere, rod and sheet).…”