Syamantak Roy

Highly Luminescent Microporous Organic Polymer with Lewis Acidic Boron Sites on the Pore Surface: Ratiometric Sensing and Capture of F− Ions

Reversible and selective capture/detection of F(-) ions in water is of the utmost importance, as excess intake leads to adverse effects on human health. Highly robust Lewis acidic luminescent porous organic materials have potential for efficient sequestration and detection of F(-) ions. Herein, the rational design and synthesis of a boron-based, Lewis acidic microporous organic polymer (BMOP) derived from tris(4-bromo-2,3,5,6-tetramethylphenyl)boron nodes and diethynylbiphenyl linkers with a pore size of 1.08 nm for selective turn-on sensing and capture of F(-) ion are reported. The presence of a vacant pπ orbital on the boron center of BMOP results in intramolecular charge transfer (ICT) from the linker to boron. BMOP shows selective turn-on blue emission for F(-) ions in aqueous mixtures with a detection limit of 2.6 μM. Strong B-F interactions facilitate rapid sequestration of F(-) by BMOP. The ICT emission of BMOP can be reversibly regenerated by addition of an excess of water, and the polymer can be reused several times.

Flexible MOF–aminoclay nanocomposites showing tunable stepwise/gated sorption for C2H2, CO2 and separation for CO2/N2 and CO2/CH4

Miniaturization of flexible metal–organic frameworks (F-MOFs) to nanoscale is expected to show interesting structural dynamics and serve numerous applications from separation and drug delivery to sensing. However, nanoscale F-MOFs or their composites have remained largely unexplored to date. Here, we present a new and facile method to stabilize F-MOF nanocrystals on an aminoclay (AC) template and study their tunable, enhanced gas adsorption and separation properties. We demonstrate miniaturization of two different 2D F-MOFs, {[Cu(pyrdc)(bpp)](5H2O)}n (F-MOF1) with a pillared-bilayer structure and {[Cu(dhbc)2(4,4′-bpy)]·H2O} (F-MOF2) with an interdigitated network, on AC that acts as a functional template to grow and stabilize MOF nanocrystals. Different F-MOF1@AC composites were synthesized where the gate/step pressure for specific adsorbate molecules (CO2/C2H2) could be tuned by varying the AC content. Enhanced guest adsorption with stepwise behaviour has also been realized in a certain composite. Breakthrough column experiments with the F-MOF2@AC composite show its capability to separate CO2/N2 and CO2/CH4 gas mixtures under ambient conditions.

Redox-active and semi-conducting donor–acceptor conjugated microporous polymers as metal-free ORR catalysts

Metal-free pristine conjugated microporous polymers (CMPs) catalyzing electrochemical oxygen reduction reaction (ORR) are still rare. We therefore put forward a design strategy to fabricate electrochemically active CMPs by linking donor nodes and acceptor spacers. The two new CMPs have been structurally well characterized and show semi-conduction and redox-activity. As a proof of concept, we show that both the CMPs have appreciable ORR activity and catalytic stability over time. Further, DFT calculations reveal the origin of the semi-conducting property and also the mode of oxygen binding to the catalytic centres. This work shows the potential application of pristine metal-free CMPs in energy conversion processes.

Two 3D supramolecular frameworks assembled from the dinuclear building block: A crystallographic evidence of carboxylate(O)…π interaction

AbstractFigure. In two new complexes of Mn(II) and Zn(II), it has been observed that carboxylate (O)…π interactions played a crucial role in the organization of supramolecular structure and that carboxylate (O)…π interactions also somehow controlled by the C-H…π interactions, which is achieved by proper modulation of the linkers. Graphical AbstractIn two new complexes of Mn(II) and Zn(II), it has been observed that carboxylate (O)…π interactions played a crucial role in the organization of supramolecular structure and that carboxylate (O)…π interactions also somehow controlled by the C-H…π interactions, which is achieved by proper modulation of the linkers.

Solvent-Modulated Emission Properties in a Superhydrophobic Oligo(p-phenyleneethynylene)-Based 3D Porous Supramolecular Framework

A chromophoric oligo( p-phenyleneethynylene) (OPE) bola-amphiphile with dioxyoctyl side chains (H2OPE-C8) has been self-assembled with CdII to form a 1D coordination polymer, {Cd(OPE-C8)(DMF)2(H2O)} (1), which is further interdigitated to form a 2D network. Such 2D networks are further interwoven to form a 3D supramolecular framework with surface-projected alkyl chains. The desolvated framework showed permanent porosity, as realized from the CO2 adsorption profile. 1 showed high water contact angles, portraying its superhydrophobic nature. 1 also showed a linker-based cyan luminescence. Solvent removal led to a bathochromic shift in emission into the green region. Resolvation with N, N-dimethylformamide brought back the original cyan emission, whereas for tetrahydrofuran, ethanol, and methanol, it persisted at an intermediate state. Density functional theory calculations unraveled that, twisting of the OPE phenyl rings generated the red shift in emission.

Nanovesicular MOF with Omniphilic Porosity: Bimodal Functionality for White-Light Emission and Photocatalysis by Dye Encapsulation

A new π-chromophoric and asymmetric bola-amphiphilic oligo-( p-phenylene ethynylene)-based tetracarboxylate (OPE-TC1) linker was designed, synthesized, and self-assembled with Zn(OAc)2. The resulting nanoscale metal-organic framework (MOF) {Zn2(OPE-TC1)} n (NMOF-1) showed a vesicular morphology and permanent porosity with omniphilic pore surface. NMOF-1 showed cyan emission with high quantum efficiency (49%). The omniphilicity of the pore was utilized to incorporate ambipolar dye sulforhodamine G (SRG) to tune the band gap as well as to get pure white-light emission. Furthermore, the polar pore surface of NMOF-1 allowed facile diffusion of the substrate for efficient photocatalytic activity. The dye-encapsulated framework further showed enhanced dihydrogen production by 1.75-fold compared to that from the as-synthesized NMOF-1 because of the modulated band gap and high excited state lifetime. As a control experiment, we have synthesized a MOF (MOF-OMe) with an OPE-TC2 linker having -OMe functional groups that did not show nanoscale architecture. This suggested the important role of unsymmetrical bola-amphiphilicity in nanostructuring. This rational design of a chromophoric linker resulted in a nanoscale MOF with omniphilic porosity to achieve bimodal functionality in clean energy applications.