Computational and Experimental Studies on the Effects of Monomer Planarity on Covalent Organic Framework Formation

Abstract

We report the synthesis of one new boronate ester-based covalent organic framework (COF) and two new covalent organic polymers (COPs) made with fluoranthene-containing monomers and hexahydroxytriphenylene. The structure of the monomer heavily influences whether this material forms a highly ordered mesoporous material (COF) or an amorphous, microporous material (COP). The synthesis of the fluoranthene monomers was carried out using a divergent strategy that allows for systematic structural variation and the ability to conduct a careful structure-function study. We found that small structural variations in the monomers dramatically affected the crystallinity, surface area, pore structure, and luminescence properties of the polymers. While each of the monomers contains the same fluoranthene core, the resultant pore sizes range from microporous (10 Å) to mesoporous (37 Å), with surface areas ranging from ∼500 to 1200 m/g. To help explain how these small structural differences can have such a large effect, we carried out a series of molecular dynamics simulations on the polymers to obtain information with atomic-scale resolution on how the monomer structure affects non-covalent COF layer stacking.

Fully sp2‐Carbon‐Linked Crystalline Two‐Dimensional Conjugated Polymers: Insight into 2D Poly(phenylenecyanovinylene) Formation and its Optoelectronic Properties

“…2D‐CN‐PPV‐2 with the BPDA spacer only shows two major reflections in the PXRD pattern, indicating moderate crystallinity (Figure b). This observation could be explained by the lower shape persistency of the starting monomers, leading to weaker interlayer π–π stacking and therefore worse alignment in the plane . The structures of all the 2D‐CN‐PPV s were optimized in typical eclipsed (AA), staggered (AB), and slipped eclipsed (slip‐AA) π–π stacking arrangements by using the density functional tight binding method.…”

“…This observation could be explained by the lower shape persistency of the starting monomers, leading to weaker interlayer p-p stacking and therefore worse alignment in the plane. [13] The structures of all the 2D-CN-PPVsw ere optimized in typicale clipsed (AA), staggered (AB), and slipped eclipsed (slip-AA) p-p stacking arrangements by using the density functional tight binding method.I th as been found that the experimental PXRD patterns of all 2D-CN-PPVsa re matched well with the simulated ones derived from the eclipsed (AA) p-p stacking arrangement ( Figures S4-1-S4-3, in the Supporting Information).…”

“…The chemical structures and long-range ordering of the targeted 2D-CN-PPVsh ave been unambiguously confirmed by Fouriert ransformed infrareds pectroscopy (FTIR), 13 Cc ross-polarization magic-angles pinning (CP-MAS) NMR spectroscopy, and powder X-ray diffraction (PXRD). To gain insighti nto the propagation mechanism of the polymerization step, we examined the essentiality of inorganic bases by means of DFTnudged elastic band (NEB) theoretical modeling.…”

The Origin of the Reproduction of Different Nitrogen Uptakes in Covalent Organic Frameworks (COFs)

“…Over the past decade, COFs have been intensively investigated in the fields of gas adsorption and separation, catalysis, energy storage and conversion, and electronic devices . In general, the application region of COFs depends on their textural peculiarity, such as functional units, pore size and surface area . In addition, some anthropogenic factors, including reagent concentrations, reaction conditions, purification procedure, degassing process, and so on, also influence the gas sorption capacity and corresponding functions of COFs .…”

“…[10] In general, the application regiono fC OFs depends on their textural peculiarity,s uch as functional units,p ore size and surface area. [11] In addition, some anthropogenic factors, including reagent concentrations, reactionc onditions, purificationp rocedure, degassingp rocess, and so on, also influence the gas sorption capacitya nd corresponding functions of COFs. [12,13] Therefore, it is reasonable that different gas isotherms were reproduced by different ex-perimental groups for the same material at the same conditions.…”