Molecular engineering of carbon nitride towards photocatalytic H2 evolution and dye degradation.

The development of superior heterogeneous catalyst for hydrogen (H2) evolution is a significant feature and challenging for determining the energy and environmental crises. However, the dumping of numerous lethal colorants (dye) as of textile manufacturing has fascinated widespread devotion-aimed water pollution anticipation and treatment. In this regard, a photocatalytic H2 evolution by visible light using low-dimensional semiconducting materials having pollutant degradable capacity for Rhodamine B dyes (RhB) has been anticipated as a route towards environmental aspect. Here we fabricated the incorporation of organic electron-rich heterocyclic monomer 2,6-dimethylmorpholine (MP), inside electron-poor graphitic carbon nitride (g-CN) semiconductor by solid-state co-polymerization. The supremacy of copolymerization process was successfully examined via absorbent, calculated band gap, and migration of electrons on the photocatalytic performance of as-constructed CN-MP copolymer. The density functional theory (DFT) calculation provides extra support as evident for the successful integration of MP into the g-CN framework by this means-reduced band gap upon co-polymerization. The hydrogen evolution rate (HER) for g-CN was found as 115.2 µmol/h, whereas for CN-PM0.1was estimated at 641.2 µmol/h (six times higher). In particular, the pseudo-order kinetic constant of CN-MP0.1 for photodegradation of RhB was two times higher than that ofg-CN. Results show an important step toward tailor-designed and explain the vital role of the D-A system for the rational motifs of productive photocatalysts with effective pollutant degradable capability for future demand.

Molecular engineering of polymeric carbon nitride based Donor-Acceptor conjugated copolymers for enhanced photocatalytic full water splitting.

Research based on the full water splitting via heterogenous semiconducting photocatalyst is a significant characteristic nevertheless challenging for determining the energy and environmental crises. With respect to this, a photocatalytic water splitting by visible light through heterojunction semiconductors has been anticipated as a route to the sustainable energy. For the first time, we integrate a potential conjugated donor-acceptor (DA) co-monomer such as 2, 3-dichloroquinoxaline (DCQ) within the structure of polymeric carbon nitride (PCN) by a facile one-pot co-polymerization process. The DCQ which is acting as an organic motif that simulates a nucleophilic attack on the hosting PCN semiconductor which extends into a long chain of the polymer having enormous surface area and remarkable photocatalytic activity for H2 and O2 evolution as compared to the parental CNU. The supremacy of molecular geometry with DA ratio is effectively studied by absorbent, calculated band gap and migration of electrons on the photocatalytic performance of as-synthesized CNU-DCQx co-polymer. The density functional theory (DFT) calculation deliver supplementary evidence for the positive incorporation of DCQ in to the PCN matrix with reduced band gap upon copolymerization. Further, the hydrogen evolution rate (HER) for pure CNU with 14.2 µmol/h while for CNU-DCQ18.0 it is estimated at 124.9 µmol/h which remarkably fueled almost eight times more than blank sample. Similarly, the oxygen evolution rate (OER) analysis indicates the production 0.2 µmol/h (visible) and 1.5 µmol/h (non-visible) for CNU. However, the OER of copolymerized CNU-DCQ18.0 is found to be 1.9 µmol/h (visible) and 12.8 µmol/h (non-visible) which almost nine times higher than parental CNU. Hence, the output of this work reflects as an important step on the way to tailor-designed and elucidate the promising role of D-π-A system for the rational motifs of productive photocatalysts for forthcoming request.

Rational Ionothermal Copolymerization of TCNQ with PCN Semiconductor for Enhanced Photocatalytic Full Water Splitting.

Photocatalytic full water splitting remains the perfect way to generate oxygen (O2) and hydrogen (H2) gases driven by sunlight to address the future environmental issues as well as energy demands. Owing to its exceptional properties, polymeric carbon nitride (PCN) has been one of the most widely investigated semiconductor photocatalysts. Nevertheless, blank PCN characteristically displays restrained photocatalytic performance due to high-density defects in its framework that may perhaps perform the part of the recombination midpoint for photoproduced electron-hole pairs. Therefore, to overcome this problem, a simple approach to introduce 7,7,8,8-tetracyanoquinodimethane (TCNQ) with an electron-withdrawing characteristic modifier into the pristine PCN framework by the ionothermal method to enhance its optical, conductive, and photocatalytic properties has been undertaken. Results show that such integration of TCNQ results in the delocalization of the π-conjugated structure; significant changes in its chemical electronic configuration, band gap, and surface area; and enhanced production of electrons under visible light. As a result of this facile integration, our best sample (CNU-TCNQ9.0) produced a hydrogen evolution rate (HER) of 164.6 µmol h-1 for H2 and an oxygen evolution rate (OER) of 14.8 µmol h-1 for O2, which were found to be 2.4- and 2.6-fold greater than those produced with pure carbon nitride (CNU) sample, respectively. Hence, this work provides a reasonable alternative method to synthesize and design novel CNU-TCNQ backbone photocatalyst for organic photosynthesis, CO2 reduction, hydrogen evolution, etc.

Synthesis and optimization of the trimesic acid modified polymeric carbon nitride for enhanced photocatalytic reduction of CO2.

The conjugated co-monomer, trimesic acid (TMA) was integrated into the triazine framework of polymeric carbon nitride (PCN), synthesized through chemical condensation of urea. The TMA-modified carbon nitride samples obtained were named as CNU-TMA and it was utilized for the photocatalytic reduction of carbon dioxide (CO2) under visible light illumination. The induction of such electron donor-acceptor co-monomer (TMA) dominates the intramolecular structure of PCN by acting as a nucleophilic substitution substrate to facilitate the electron density in the π-electron conjugated system of PCN and thus elevate its photocatalytic activity. Also, this process of copolymerization with TMA, not only cause a significant diversion in the specific area, band gap, chemical composition, and structure of PCN but also promote efficient charge transport from ground state (HOMO) to the excited state (LUMO) of the PCN. For comparison, CNU samples modified with other co-monomers were prepared by the same method and were named as CNU-FDA (2,5-Furandicarboxylic acid), CNU-PDA (2,6-pyridinedicarboxylic acid), CNU-PTA (Phthalic acid). Similarly, co-monomer TMA was incorporated in other PCN precursors such as dyandicyanamide (DCDA), thiourea (SCN) and ammonium thiocyanate (NH2SCN) and was named as CND-TMA13.0, CNT-TMA13.0, and CNA-TMA13.0, respectively. Besides, the average weight ratio between urea and TMA was well tuned and also CNU-TMA13.0 gain a fabulous 16 fold-enhanced photocatalytic performance than blank CNU.