The exfoliation of covalent organic frameworks into covalent organic nanosheets (CONs) not only helps to reduce fluorescence turn-off phenomena but also provides well-exposed active sites for fast response and recovery for various applications. The present work is an example of rational designing of a structure constructed by condensing triaminoguanidinium chloride (TG Cl ), an intrinsic ionic linker, with a fluorophore, 2, 5dimethoxyterephthalaldehyde (DA), to produce highly fluorescent selfexfoliable ionic CONs (DATG Cl -iCONs). These fluorescent iCONs are able to sense fluoride ions selectively down to the ppb level via the fluorescence turn-off mechanism. A closer look at the quenching mechanism via NMR, zeta potential measurement, lifetime measurement, and density functional theory calculations reveals unique proton-triggered fluorescence switching behavior of newly synthesized DATG Cl -iCONs.

Herein, we have reported two benzothiazole-linked covalent organic framework nanostructures (BTZ-BCA-COF and BTZ-TPA-COF), which have been prepared via a highly efficient one-pot, multicomponent transition-metal-free C−H functionalization and oxidative annulation synthetic strategy and employing elemental sulfur as one of the key components. These prepared COFs are highly crystalline in nature, have high surface area, and are chemically stable. These COFs exhibit light-harvesting capacity as a photosensitizer for visible-light-assisted "carbon−boron" bond cleavage with a high functional group tolerance of the substrates. In order to acquire in-depth understanding about the mechanistic pathway involved and for comparison in photocatalytic performance, we have performed in situ electron paramagnetic resonance and studies. Our contribution sheds light on exploration of elemental sulfur to extended π-conjugation network-based photocatalysts, followed by instigating their structural uniqueness− photocatalytic activity relationship.

Covalent organic frameworks (COFs) offer great potential for various advanced applications such as photocatalysis, sensing, etc., because of their fully conjugated, porous, and chemically stable unique structural architecture. In this work, we have designed and developed a truxene based ultrastable COF (Tx-COF-2) by Schiff-base condensation between 1,3,5-Tris(4-aminophenyl)benzene (TAPB) and 5,5,10,10,15,15-hexamethyl-10,15-dihydro-5H-diindeno(1,2-a:1',2'-c)fluorene-2,7,12-tricarbaldehyde (Tx-CHO) for the first time. The resulting COF possesses excellent crystallinity, permanent porosity, and high Brunauer-Emmett-Teller (BET) surface areas (up to 1137 m 2 g -1 ). The COF was found to be a heterogeneous, recyclable photocatalyst for efficient conversion of arylboronic acids to phenols under visible-light irradiation, an environmentally friendly alternative approach to conventional metalbased photocatalysis. Besides, Tx-COF-2 provides an immediate naked-eye color change (<1s) and fluorescence 'turn-on' phenomena upon exposure to HCl. The response is highly sensitive, with an ultra-low detection limit of up to 4.5 nmol L -1 .

Luminescent conjugated microporous polymers (CMPs) are one of the important class of porous organic materials that possess a fully π-conjugated skeleton and high surface area and have been utilized as light-emitting materials. In this work, we have designed and developed three luminescent CMPs based on truxene core (Tx-CMPs) via Suzuki−Miyaura cross-coupling reaction in one step. The flexible aryl linker in Tx-CMPs prevents the possibility of aggregation-caused quenching (ACQ) due to π−π stacking of layers and thus offers a high luminescence in the synthesized Tx-CMPs. All Tx-CMPs possess a high BET surface area (S BET = 788−915 m 2 g −1 ) and excellent thermal stability. Utilizing the fluorescent nature and electron-rich property of the Tx-CMPs, we exploited them as a sensor for the selective and sensitive detection of picric acid (PA) among various nitroaromatic explosives. The Stern−Volmer constant (K SV ) for PA was estimated as 3.97 × 10 4 , 7.35 × 10 4 , and 2.39 × 10 4 M −1 for Tx-CMP-1, Tx-CMP-2, and Tx-CMP-3, respectively, indicating that PA can quench the fluorescence intensity of Tx-CMP-2 most efficiently. The detection limits of Tx-CMPs toward PA were found in the nanomolar range.

The rational synthesis of durable, earth-abundant efficient electrocatalysts for the oxygen evolution reaction (OER) from water is one of the most significant routes for storing renewable energy and minimizing fossil...

Covalent organic frameworks (COFs) are the emerging smart materials that can be designed and synthesized by tuning their structural diversity and topology for various applications. Despite vast advancements in the design of COFs, the synthetic methodologies to construct COFs are always a significant challenge. Herein, we demonstrate a fast crystallization in hydrazone-based Bth-Tp-COF, synthesized via a Schiff-base reaction between benzene-1,3,5-tricarbohydrazide (Bth) and triformylphloroglucinol (Tp) linkers under stirred conditions. The growth of the COF was typically completed in 30 min and likely driven by intra- and interlayer hydrogen bonding in COF layers, leading to the fast crystallization. Here, the intralayer hydrogen bonding prevented in-plane bond rotation, while the interlayer hydrogen bonding provided rigidity to the COF layers favoring the antiparallel stacking model. The synthesized Bth-Tp-COF was found to be highly stable in harsh chemicals such as 12 M HCl, 12 M NaOH, TFA, and water for 5 days. Moreover, when we doped palladium (Pd) in Bth-Tp-COF, the resulting Pd/Bth-Tp-COF was found to be a highly efficient heterogeneous catalyst for the Suzuki–Miyaura cross-coupling reaction that completed in a quick reaction time of only 20 min with excellent yields. In addition, Pd/Bth-Tp-COF displayed high activity in the recycling experiment with a slight decrease in its crystallinity up to five catalytic cycles. The fast crystallization and metal doping strategy in COFs open up several opportunities to develop excellent heterogeneous catalysts for various chemical transformations.

Nanoscale assemblies of amphiphiles have been vividly explored in pharmaceutical formulations as drug nanocarriers. Aqueous interfaces of liquid crystals (LCs) are known to direct the self-assembly of a range of...