Anatomy of On-Surface Synthesized Boroxine Two-Dimensional Polymers

Abstract

Synthetic 2D polymers (2DPs) obtained from well-defined monomers via bottom up fabrication strategies are promising materials that can extend the realm of inorganic 2D materials. The on-surface synthesis of such 2DPs is particularly popular, however the pathway complexity in the growth of such films formed on solid surfaces is poorly understood. In this contribution, we present a straightforward experimental protocol which allows the synthesis of large area, defect-free 2DPs based on boroxine linkages at room temperature. We focus on unravelling the multiple pathways available to the polymerizing system for the spatial extension of the covalent bonds. Besides the anticipated 2DP, the system can evolve into self-assembled monolayers of partially fused monodisperse reaction products that are difficult to isolate by conventional synthetic methods, or remain in the monomeric state. The access to each pathway can be controlled via monomer concentration and the choice of the solvent. Most importantly, the unpolymerized systems do not evolve into the corresponding 2DP upon annealing, indicating the presence of strong kinetic traps. Using high resolution scanning tunneling microscopy (STM), we show reversibility in the polymerization process where the attachment and the detachment of monomers to 2DP crystallites could be monitored as a function of time. Finally, we show that the way the 2DP grows depends on the choice of the solvent. Using UV-Vis absorption and emission spectroscopy, we reveal that the dominant pathway for 2DP growth is via in-plane self-condensation of the monomers whereas in the case of an aprotic solvent the favored growth mode is via π stacking of the monomers.

Controllable Synthesis and Performance Modulation of 2D Covalent–Organic Frameworks

“…[23] Since then, large areas of interests have been put on towards developing B-COFs with long-range ordered, tunable structures, and easy to functionalize. [111][112][113] In the view of these promising applications, microcrystal B-COFs are quite desirable for the construction of highly emissive materials as their tunable photophysical properties. Jiang made a first move on the exploration of emissive B-COFs through installing aromatic fluorescent chromophores pyrene and triphenylene into 2D frameworks.…”

Assessment of the Latrine Facilities and the Health Condition in IDP Camps in Borno State

“…According to Family Health International (FHI), 360 (2015) all the camps have reported cases of trauma, skin infection, anemia, measles, chicken pox, vomiting, fever, diarrhea, cholera, and malnutrition. About 64% of the camps have reported HIV cases [12][13][14][15][16][17][18]. All these diseases can be because of inadequate or non-functional sanitation facilities thereby questioning the operational efficiencies of the sanitary facilities provided in the camps.…”

Mass Transfer in Boronate Ester 2D COF Single Crystals

“…Although 2D COFs could be exfoliated from polymerized monomer crystals, the size of the flakes obtained was typically limited to a few hundreds of nanometers. [ 10,11 ] The bottom‐up polymerization on solid surfaces also yielded too small crystallites of the same scale, [ 12 ] while reactions at gas–liquid and liquid–liquid interfaces gave rise to macroscopic films with a low degree of long‐range order. [ 13 ] Only recently, Feng and co‐workers developed surfactant‐monolayer‐assisted interfacial synthesis (SMAIS) of centimeter‐sized single‐ and few‐layer 2D polymers with crystalline domains as large as several micrometers.…”