Emerging Chemical Functionalization of g-C₃N₄: Covalent/Noncovalent Modifications and Applications

Abstract

Atomically 2D thin-layered structures, such as graphene nanosheets, graphitic carbon nitride nanosheets (g-C3N4), hexagonal boron nitride, and transition metal dichalcogenides are emerging as fascinating materials for a good array of domains owing to their rare physicochemical characteristics. In particular, graphitic carbon nitride has turned into a hot subject in the scientific community due to numerous qualities such as simple preparation, electrochemical properties, high adsorption capacity, good photochemical properties, thermal stability, and acid-alkali chemical resistance, etc. Basically, g-C3N4 is considered as a polymeric material consisting of N and C atoms forming a tri-s-triazine network connected by planar amino groups. In comparison with most C-based materials, g-C3N4 possesses electron-rich characteristics, basic moieties, and hydrogen-bonding groups owing to the presence of hydrogen and nitrogen atoms; therefore, it is taken into account as an interesting nominee to further complement carbon in applications of functional materials. Nevertheless, g-C3N4 has some intrinsic limitations and drawbacks mainly related to a relatively poor specific surface area, rapid charge recombination, a limited light absorption range, and a poor dispersibility in both aqueous and organic mediums. To overcome these shortcomings, numerous chemical modification approaches have been conducted with the aim of expanding the range of application of g-C3N4 and enhancing its properties. In the current review, the comprehensive survey is conducted on g-C3N4 chemical functionalization strategies including covalent and noncovalent approaches. Covalent approaches consist of establishing covalent linkage between the g-C3N4 structure and the chemical modifier such as oxidation/carboxylation, amidation, polymer grafting, etc., whereas the noncovalent approaches mainly consist of physical bonding and intermolecular interaction such as van der Waals interactions, electrostatic interactions, π–π interactions, and so on. Furthermore, the preparation, characterization, and diverse applications of functionalized g-C3N4 in various domains are described and recapped. We believe that this work will inspire scientists and readers to conduct research with the aim of exploring other functionalization strategies for this material in numerous applications.

Upgrading poly(styrene‐co‐divinylbenzene) beads: Incorporation of organomodified metal‐free semiconductor graphitic carbon nitride through suspension photopolymerization to generate photoactive resins

“…As a heterogeneous photocatalyst, it has been used in many applications such as water splitting, hydrogen evolution, CO 2 reduction and degradation of aqueous contaminants 3,7–10 . Moreover, tunable morphology and composition along with the facile functionalization brings a rich chemical diversity 11–13 . Very recent review by Zhang and colleagues nicely describes the synthesis of diverse carbon nitride materials and their corresponding electronic properties and applications, thus underlining the emergent interest on g‐CN family 14 .…”

Oxidative Photopolymerization of 3,4‐Ethylenedioxythiophene (EDOT) via Graphitic Carbon Nitride: A Modular Toolbox for Attaining PEDOT**

“…Graphitic carbon nitride (g‐CN, g‐C 3 N 4 ) is a semiconductor polymer that is mainly composed of nitrogen and carbon atoms in a conjugated framework, such as tri‐s‐triazine [15] . g‐CN represents a family of materials with facile tunability such as bandgap, work function, surface properties and elemental doping in the framework [16,17] . Furthermore, its non‐toxic and highly stable character together with the synthesis from low cost and abundant precursors (i. e. melamine, urea, dicyandiamide) place g‐CN as a new generation semiconductor to be investigated in fields such as photocatalytic water splitting, CO 2 reduction, pollutant degradation and light‐induced sanitization [18–23] .…”

In‐depth Understanding of the Effects of Intramolecular Charge Transfer on Carbon Nitride Based Photocatalysts†

“…As a polymeric visible‐light responsive photocatalyst, graphitic carbon nitride (GCN) attracts a lot of attention with facile preparation, high thermo‐/chemical stability, and high photocatalytic efficiency. [ 13‐15 ] Unfortunately, the majority of GCN materials still suffer from some drawbacks, including limited light harvesting, poor charge mobility, low crystallinity, surface defects, etc . Though numerous methods have been discovered to overcome the aforementioned shortcomings, the state of the art provides a plethora of performed GCN modifications including constructing heterojunctions between the interface of GCN and other semiconductors, [ 16‐18 ] morphology control and porosity introduction by template synthesis, [ 19‐20 ] elemental doping, [ 21‐23 ] etc .…”

“…In the community of modification engineering, lots of reviews and surveys on the latest advances from various aspects are indispensable for the promotion of GCN, such as structure and property control via liquid precursor polymerization, [ 24‐25 ] GCN based heterogeneous catalysts, [ 26‐27 ] the advancements in different domains, [ 28‐30 ] polymer/GCN hybrid materials with advanced applications [ 31 ] and covalent/noncovalent modifications. [ 13 ] However, there is a lack of in‐depth understanding of the changes in ICT induced electronic structure in GCN materials at molecular level after the molecular coupling/modification. In this regard, it is urgent to establish a timely, comprehensive, in‐depth review focusing on the ICT mediated light absorption and charge separation of GCN, aiming to enrich the recognition of GCN based photocatalysts’ modification in all‐round dimension.…”