# Synergistic Gas-Bubbling and Oxidative Exfoliation for the Reproducible Synthesis of Mesoporous g‑C3N4 2D Nanosheets with Enhanced Physicochemical Properties

## TL;DR

A new method for making mesoporous g-C3N4 nanosheets improves their photocatalytic performance by enhancing their structure and properties.

## Contribution

A synergistic gas-bubbling and oxidative exfoliation method enables reproducible synthesis of mesoporous g-C3N4 nanosheets with enhanced photocatalytic activity.

## Key findings

- The new method produces thin g-C3N4 nanosheets with increased band gap and surface area.
- The nanosheets show 4 times higher photoactivity compared to pristine g-C3N4.
- Charge carrier lifetimes and nitrogen vacancies are enhanced through the proposed synthesis protocol.

## Abstract

2D nanosheets of graphitic carbon nitride (g-C3N4) have emerged as promising metal-free photocatalyst.
However,
their reproducible preparation with a control of physiochemical properties
is challenging, and the commonly used thermal polymerization method
often leads to the formation of bulk g-C3N4 with
faster e––h+ recombination and
low surface area, which hinder its full photocatalytic potential.
To address these limitations and obtain highly exfoliated and mesoporous
2D nanosheets of g-C3N4 (EmNs) with desirable
physiochemical properties, we propose a facile and reproducible collaborative
strategy, based on the synergistic use of ammonium salts as a dynamic
gas template and oxidative exfoliation (OE). The prepared EmNs were
characterized by an array of complementary analytical techniques including
XRD, DRS, EPR, NMR, TEM, SEM-EDX, Raman Spectroscopy, LC-DAD-MS, and
time-resolved photoluminescence (PL) measurements and their photoactivity
was evaluated through photodegradation of rhodamine B (RhB) dye and
2,4-D herbicide as model pollutants. The proposed one-pot, two-steps
thermochemical synthesis protocol not only leads to the preparation
of thin (12 ± 3 nm) EmNs but also allows the tuning of their
electronic structure, band gap, textural properties, nitrogen vacancies
(N-vacancies), and photocatalytic response. Importantly, the band
gap energy (E
g), specific surface area,
number of N-vacancies, and lifetimes of charge carriers (63–69
ns in EmNs vs 47 ns in pristine g-C3N4) were
all found to increase with increasing NH4Cl/melamine ratio
and after OE treatment in a synergistic manner. Resultantly, the prepared
g-C3N4 EmNs exhibited 4 times higher photoactivity
(k
obs. = 0.09 min–1)
than pristine g-C3N4 (k
obs. = 0.023 min–1). This one-pot, two-step
collaborative strategy can be used as an optimized protocol for the
reproducible preparation of thin, highly photoactive, and mesoporous
g-C3N4 nanosheets with tailored and enhanced
physicochemical properties for desired applications.