![]() ![]() #Best mspe noteworthy characteristics reddit seriesHerein, we report our efforts to synthesize a series of crystalline and highly dispersive 2D CPs with 3D trifunctional triptycene monomers ( Figure 1). On the basis of continuing interests in exploring the unique influence of isomerism on the properties of polymers, (49,50) we envision that the distinct linking group arrangements of trifunctionalized 3D monomers would have a profound influence on the orientation of polymer growth, which in turn allows the manipulation of the crystallinity and the morphology of COFs/CPs via regioisomerism. However, the limited persistence of these boronate ester-based materials hampers their potential for long-term utility. (47) There is only one example of crystalline 2D layered COF built with triptycene monomers that benefits from the superior reversibility of the boronate ester linkage. (43−45) Recently, the triptycene-based linkers were utilized to construct covalently bonded porous organic nanotubes (CONTs), wherein interesting self-assembly properties were observed. demonstrated that the use of triptycene-based building blocks could lead to 3D COFs with remarkable gas adsorption capabilities. The successful examples usually require highly symmetric hexafunctionalized monomers and afford 3D COFs with diverse topologies. (42) In contrast, the use of triptycene-based building blocks to prepare highly crystalline COFs/CPs is rare. (39−41) Although the concaved shape of triptycene is supposed to prevent condensed packing, imparting high surface areas, triptycene-derived porous materials are often amorphous and are lacking well-defined pore structures. (33−38) A structural inquiry in Cambridge Crystallographic Database on the triptycene-based molecular crystals disclosed that the packings with C–H bonding pointing toward the interlayer space are not unusual ( Figures S1 and S2 in the Supporting Information). Owing to their unique rigid 3D scaffolds, triptycenes have been extensively explored in a variety of porous polymeric material platforms, such as polymers of intrinsic microporosity (PIMs), conjugated microporous polymers (CMPs), porous aromatic frameworks (PAFs), and covalent triazine frameworks (CTFs). The triptycene-based monomers are ideal candidates to prepare the above-mentioned 2D COFs/CPs with C–H bonds facing the (100) planes. More recently, Loh et al demonstrated that the self-exfoliation of COFs can be achieved via the formation of backbone pseudorotaxanes, which allows the controllable partition of the interlayer space. This robust approach also offers opportunities to introduce in-pore functionalities that are essential for superior gas separation and catalysis. (28,29) The molecular engineering of building blocks is another appealing strategy to modulate the interaction between layers, where the charge, steric hindrance, and dipole moments of the incorporated side chains influence the tendency of COFs to aggregate. However, these methods are destructive and often lead to COFs of reduced structural integrity and crystallinity. (21−27) The treatment of COFs with strong acids, bases, or high-energy ultrasound is a viable way to destroy the interlayer interactions, affording dispersed COF nanosheets in solution. As a consequence, there has been a growing interest in new strategies for accessing exfoliated COF nanosheets with a few layers ( n < 10). (18−20) However, the strong π–π stacking interactions between layers often lead to severe aggregation and poor dispersibility, which are detrimental to processibility and efficient substrate/molecule translocation within the material. (8−17) As the π–π stacking between the transient oligomeric intermediates is beneficial to self-correction and the formation of highly ordered assembly, highly crystalline layered two-dimensional (2D) COFs built solely with planar monomers are usually considered more accessible than those composed of three-dimensional (3D) structural units. To ensure a high crystallinity, COFs are usually constructed with planar building blocks of high symmetry. (1−7) Among various CPs, covalent organic frameworks (COFs) have attracted increasing attention owing to their tailorable pore sizes and the ease of structural elaboration for applications ranging from gas adsorption, separation, catalysis, and optoelectronics to energy storage. Crystalline polymers (CPs) assembled with covalent bonds often possess tunable chemical structures and large surface areas. ![]()
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