Interfacially synthesized 2D COF thin film photocatalyst: efficient photocatalyst for solar formic acid production from CO2and fine chemical synthesis

Article abstract of DOI:10.1039/d1ta00802a

The targeted synthesis of an efficient, visible light active, recyclable, freestanding covalent organic framework thin film photocatalyst for multi-faceted photocatalysis is the essence of the proposed work. A simple, scalable, reagent free synthesis of a thin film at the interface of 5,10,15,20-tetra-(4-aminophenyl)porphyrin, 2-vinylbenzene-1,4-dicarbaldehyde in nitrobenzene and aqueous glyoxal affords centimetre sized continuous 2D thin film with substantial stability, flexibility and efficient visible light activity. Strikingly different from the regular imine based COF, the incorporation of the glyoxal unit as a modulator helps in band gap tuning and induces flexibility within the thin film. An interplay between time and concentration helps in achieving a thin film photocatalyst with efficient photocatalytic activity for 1,4-NADH regeneration and selective formic acid formation from CO₂. The optimum band edge position of the thin film photocatalyst also enables solar fine chemical synthesisviareductive dehalogenation under visible light illumination with excellent recyclability. The present work gives insight into visible light active thin film formation en route to metal-free sustainable photocatalysis.

Full text of DOI:10.1039/d1ta00802a

Volume 9
Number 15
21 April 2021
Pages 9373–9962
Journal of
Materials Chemistry A
Materials for energy and sustainability
rsc.li/materials-a
ISSN 2050-7488
PAPER
Jin-Ook Baeg et al.
Interfacially synthesized 2D COF thin film photocatalyst:
efficient photocatalyst for solar formic acid production
from CO2 and fine chemical synthesis

Journal of
Materials Chemistry A
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PAPER
Interfacially synthesized 2D COF thin film
photocatalyst: efficient photocatalyst for solar
formic acid production from CO2 and fine chemical
synthesis†
Cite this: J. Mater. Chem. A, 2021, 9,
9573
a
b
a
a
Dolly Yadav,
Abhishek Kumar,
Jae Young Kim,
No-Joong Park
a
*
and Jin-Ook Baeg
The targeted synthesis of an efficient, visible light active, recyclable, freestanding covalent organic
framework thin film photocatalyst for multi-faceted photocatalysis is the essence of the proposed work.
A simple, scalable, reagent free synthesis of a thin film at the interface of 5,10,15,20-tetra-(4-
aminophenyl)porphyrin, 2-vinylbenzene-1,4-dicarbaldehyde in nitrobenzene and aqueous glyoxal affords
centimetre sized continuous 2D thin film with substantial stability, flexibility and efficient visible light
activity. Strikingly different from the regular imine based COF, the incorporation of the glyoxal unit as
a modulator helps in band gap tuning and induces flexibility within the thin film. An interplay between
time and concentration helps in achieving a thin film photocatalyst with efficient photocatalytic activity
for 1,4-NADH regeneration and selective formic acid formation from CO2. The optimum band edge
position of the thin film photocatalyst also enables solar fine chemical synthesis via reductive
dehalogenation under visible light illumination with excellent recyclability. The present work gives insight
into visible light active thin film formation en route to metal-free sustainable photocatalysis.
Received 28th January 2021
Accepted 29th March 2021
DOI: 10.1039/d1ta00802a
rsc.li/materials-a
thickness of the synthesized thin lm. And between various
plausible combinations, the liquid–liquid interface is consid-
ered to be the best for obtaining 2D materials9–12 as it provides
Introduction
Thin lms are highly sought aer materials for industrial and
academic purpose due to their wide application in the elds of
optics and electronics, as nanosensors and in nanoltration
devices.1,2 Although inorganic semiconductor thin lms have
been successfully commercialized analogous examples of
organic thin lms are extremely rare. Among organic materials,
COF thin lms are most promising due to the vast variety of
systems that can be synthesized depending on the targeted
application. However, the processability of COFs into thin lms
is highly challenging, as once synthesized the COFs have
negligible solubility in common organic solvents. As a result,
the fabrication of COFs into stable, self-standing, crystalline,
and porous thin lms remains a major challenge that has yet to
be overcome.3
excellent mobility to the reactants and induces 2D conned
reaction even under mild synthetic conditions. Moreover, the
liquid interface allows the formation of free-standing lms,
which can be transferred onto other desired surfaces, for
structural characterization or device fabrication. Due to the
exibility of liquid surfaces, the lms produced on a liquid
surface can be folded, bent, stretched, and compressed. What-
soever, such high motional freedom of lms is extremely chal-
lenging to achieve with solid materials. Therefore the use of
liquid–liquid interfacial polycondensation could be an ideal
fabrication methodology to obtain 2D COF thin lm for pho-
tocatalytic applications.13
For the targeted development of a robust 2D COF based thin
lm photocatalyst with excellent photocatalytic activity and
durability, the choice of components for lm fabrication is also
crucial. In this regard, porphyrins which have been widely
explored for biomimetic light-harvesting applications could be
an ideal starting point.14 It is interesting to note that in supra-
molecular structures the porphyrins are arranged parallel to
one other leading to the overlap of the p-orbitals, forming
eclipsed stacked 2D layers. Such a stacking phenomenon can
induce a strong electrophilic couple between the overlapped p-
orbitals to form p-electron channel thus facilitating smooth
Amongst various techniques to synthesize thin lms4–8
interfacial synthesis gives precise control over the size and
aArticial Photosynthesis Research Group, Korea Research Institute of Chemical
Technology (KRICT), 100 Jang-dong, Yuseong, Daejeon 34114, Republic of Korea.
E-mail: jobaeg@krict.re.kr
bDepartment of Chemistry, Institute of Science, Banaras Hindu University, Varanasi-
221005, India
† Electronic supplementary information (ESI) available: Synthesis, experimental
and characterization details. The NMR data and table for literature survey,
recyclability and stability data. See DOI: 10.1039/d1ta00802a
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transportation of photoinduced carriers upon illumination with efficiently catalyze the reductive dehalogenation of a-bromoa-
visible light. Indeed, porphyrins are well known to catalyze cetophenones under mild reaction conditions in presence of
numerous catalytic reactions including light assisted reac- visible light. To the best of our knowledge, this is the rst
tions.15,16 Hence designed synthesis of porphyrin based thin example of porphyrin based 2D COF freestanding thin lm to be
lms with considerable robustness and recyclable efficiency used as photocatalyst for photobiocatalytic production of for-
would prove to be a boon for attaining sustainability in the mic acid from CO2 as well as visible light driven organic
elds of photocatalysis.
transformation reaction. It is to be noted that the proposed
Keeping in view these points, we now herein report the work can also prove to be a candidate of interest for the devel-
designed synthesis of free standing porphyrin-based 2D COF opment of lm based devices for sustainable production of ne
thin lm (PTF) as an articial leaf utilizing 5,10,15,20-tetra-(4- chemicals driven by solar light.17
aminophenyl)
porphyrin
(TAPP),
2-vinylbenzene-1,4-
dicarbaldehyde (VBD) and aqueous glyoxal via liquid–liquid
interfacial synthesis (Scheme 1). By adjusting the synthetic
parameters like concentration of reactants and reaction time,
a continuous lm of desired size and thickness could be
synthesized and was transferable to any surface. The as
synthesized PTF was used as thin lm photocatalyst exhibiting
excellent reduced nicotinamide adenine dinucleotide (1,4-
NADH) regeneration up to 98.54% and selective formic acid
formation 334.1 mmol from CO2 in presence of formate dehy-
drogenase (FDH) enzyme under visible light illumination.
Besides, the PTF photocatalyst also showed efficient NADH
regeneration efficiency up to six cycles with negligible loss in
photocatalytic activity. Interestingly, the optimum band edge
position of the synthesized PTF thin lm, it was also found to
Results and discussions
The porphyrin based thin lm was synthesized via interfacial
condensation reaction between TAPP and VBD in nitrobenzene
ꢀ
and aqueous glyoxal at 51 C. In this process aqueous glyoxal
was layered onto a solution of TAPP and VBD in nitrobenzene
(Scheme S1, ESI†). The formation of thin lm was observed aer
a minute of layering. A gradual increase in thickness of the thin
lm was observed with time. The PTF lm was designated as
PTF-1min, PTF-15min, PTF-1h and PTF-12h for 1 min, 15 min,
1 h and 12 h interfacial reaction time respectively. The PTF lm
could be transferred by pipetting out the top aqueous layer and
shing out the lm on the desired substrate. The lm could also
be transferred to a solid substrate by placing the substrate
Scheme 1 (a) Synthetic scheme (b) interfacial synthesis of PTF (c) PTF photocatalyst transferred on PET substrate with tentative ball and stick
stacking diagram of PTF photocatalyst.
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under the oating lm and slowly removing the solvent until
the lm fell on to the substrate (Scheme S1, ESI†).
The effect of time on the thickness of PTF was very prom-
inent as shown in Fig. 1a–h and Table S1 in the ESI.† A gradual
increase in the thickness of the lm was observed with increase
in interfacial crystallization time. The eld emission scanning
electron microscope (FE-SEM) images of PTF (Fig. 1e–h) showed
a thickness of 97 nm obtained aer one min of interfacial
synthesis (Fig. 1e), which gradually increased to 215.6 nm in 15
minutes (Fig. 1f), 1.45 mm in 1 h (Fig. 1g) and a maximum
thickness of 8.45 mm was observed aer 12 h of interfacial
synthesis (Fig. 1h). Similar trend in the increase in thickness
with reaction time was also evident from the atomic force
microscopy (AFM) images of PTF photocatalyst. A gradual
increase in the roughness of the lm surface was observed from
9.5 nm for 1 min to 120 nm for 12 h of reaction time (Fig. 1a–d).
The high-resolution transmission electron microscope
(HRTEM) data for PTF is depicted in Fig. 2b–f. The optical
image of PTF on TEM grid shows formation of stable free
standing thin lm. Considerable difference in the morphology
of the PTF thin lm with respect to their interfacial reaction
time was observed. In one minute interfacial reaction time
(Fig. 2c, inset) development of fringes is observed which
becomes more prominent as the reaction time was increased to
15 min indicating an increase in crystallinity with reaction time.
The X-ray diffraction analysis (XRD) for PTF photocatalyst
The growth process of PTF photocatalys
The interfacial synthesis of thin lm was observed with varying
different reaction conditions. The concentration of the reac-
tants and the span for interfacial synthesis were the major
factors determining the morphology of thin lm. The area of
thin lm varied according to the area of the reaction ask. A
concentration gradient of 0.1 M to 1 M for TAPP was screened
for the lm formation, where 0.5 M was found to be an
optimum concentration for facile free standing thin lm
formation. A concentration lower than 0.5 M resulted in the
formation of a very fragile lm which developed multiple cracks
while transferring onto the desired substrate. A concentration
higher than 0.5 M resulted in thicker lm formation with lots of
spherical depositions as shown by its (Fig. S1a–c, ESI†) very
similar to the powder PTF sample (Fig. S1d, ESI†). Aer
screening the optimum concentration, the effect of time on
interfacial synthesis was monitored until 12 h.
Fig. 2 (a) Optical image of PTF photocatalyst on TEM grid. HR-TEM
images of PTF photocatalyst synthesized with difference of interfacial
Fig. 1 AFM images of PTF interfacial synthesis time (a) 1 min, (b) 15 min, reaction time. (b and c) 1 min interfacial reaction time under different
(c) 1 h and (d) 12 h. FE-SEM images of PTF interfacial synthesis time (e) magnifications. (d) 15 min interfacial reaction time. (e) 1 h interfacial
1 min, (f) 15 min, (g) 1 h and (h) 12 h.
reaction time, and (f) 12 h interfacial reaction time.
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displayed prominent diffraction peak at 21ꢀ, commonly entire visible region with Soret band and Q-bands typical of
observed for the porphyrin based COFs (Fig. S2, ESI†).16b,c
porphyrins. The diffuse reectance spectra obtained for PTF
The Fourier-transform infrared spectra (FT-IR) of PTF pho- freestanding thin lm samples on glass coverslip displayed
tocatalyst (Fig. S3, ESI†) revealed new vibrational bands at the considerable broadening in their Soret and Q-bands with
1600 cmꢁ1, that was assigned to the stretching mode of imine a slight red shi in the Soret bands.19 The UV-visible absorption
(–C]N) bonds.16a,b The X-ray photoelectron spectroscopy (XPS) spectra of VBD and TAPP (Fig. S6, ESI†) are shown for
also supported the presence of three different N 1s species comparison. The optical band gap was calculated from the Tauc
(Fig. S5, ESI†) in the PTF photocatalyst corresponding to the plot as shown in the inset of Fig. 3a–d) with values of 2.43 eV,
pyrolic (N1) and iminic (N2) nitrogen of porphyrin and the COF 2.40 eV, 2.45 eV and 2.31 eV for PTF photocatalyst (PTF-1min,
imine –C]N– (N3) respectively. The absence of N 1s signal PTF-15min, PTF-1h and PTF-12h respectively). The UPS spectra
ꢂ400–405 eV indicated successful imine bond formation in PTF for all the four PTF photocatalyst (Fig. 3 was used to determine
photocatalyst.17,18
their energy level of valance band maxima (EVB). The EVB (vs.
The optical properties of PTF photocatalyst was investigated vacuum level) was calculated by subtracting the UPS width from
through UV-diffuse reectance spectroscopy and (UV-DRS), excitation energy (He I, 21.22 eV). The EVB of ꢁ5.27, ꢁ5.47 and
ultraviolet photoelectron spectroscopy (UPS) and photo- ꢁ5.14 eV was calculated for PTF-1min, PTF-15min and PTF-1h,
luminescence studies. The UV-DRS spectra of PTF photocatalyst respectively. Further, upon combining the aforementioned
as shown in Fig. 3a, displayed panchromic absorption in the optical band gap, the conduction band minimum (ECB) could be
Fig. 3 DRS-UV absorbance spectra of PTF photocatalyst synthesized with difference of interfacial reaction time (a) PTF-1min (b) PTF-15min (c)
PTF-1h and (d) PTF-12h. The UPS spectra of (e) PTF-1min (f) PTF-15min and (g) PTF-1h. (h) Time resolved PL decay spectra (lex ¼ 505 nm) and (i)
transient photocurrent of the PTF photocatalyst.
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calculated as ꢁ2.84, ꢁ3.07 and ꢁ2.69 eV for PTF-1min, PTF-
15min and PTF-1h, respectively. For comparison all the data for
the four PTFs were collected in Table S2 in ESI.†
A longer lifetime is essentially required for enhanced sepa-
ration of charges in order to have a higher probability of
participation of photogenerated charges in the photocatalytic
reactions and hence, for enhanced photocatalytic activity.20 The
time-resolved uorescence decay spectroscopy was performed
to get information about the average lifetime of photo-excited
electrons. The time-resolved uorescence decay curves of all
four PTF photocatalyst were tted and a bi-exponential lifetime
decay curve were obtained for PTF-1min, PTF-15min, PTF-1h
and PTF-12h with the average lifetimes of 2.99, 7.9, 1.68 and
0.96 ns, respectively (Fig. 3h and Table S3, ESI†). The photo-
electrochemical measurements were conducted using three-
electrode set-up comprising of Ag/AgCl as reference, platinum
electrodes as counter and PTF thin lm as working electrode
using phosphate buffer solution as electrolyte solution. The PTF
thin lm photo-electrode was prepared by layering PTF thin lm
on FTO glass glued to copper wire via silver paste and masked
by conducting adhesive. A noticeable photoanode current could
be observed from the chopped photocurrent prole (25 s each)
of PTF thin lm (Fig. 3i), the generation of electron–hole pairs
Fig. 4 Reaction conditions: photocatalyst film, a-bromoacetophe-
in PTF thin lm upon light irradiation. The positive photocur- none (0.4 mmol), hantzsch ester (0.44 mmol), DIEPA (0.9 mmol),
anhydrous acetonitrile (3 mL) under visible light.
rent suggests that the material behaves as an n-type semi-
conductor under visible light irradiation. The measure of
photocurrent was highest for PTF-15min with an intensity of 15
detailed mechanism is depicted in Scheme S4, ESI.† A
comparative literature survey for the current performance of
reductive dehalogenation of a-bromoacetophenones is given in
Table S5, ESI.†
mA which was nearly 15 times higher than PTF-12h. The higher
photocurrent in PTF-15min is indicative of the fact that it is
most efficient in generating charge carriers upon light illumi-
nation with enhanced electron–hole separation.
Similarly, the photocatalytic reduction of CO2 to formate
requires a formal transfer of a hydride (two electrons, one
proton) via biochemical, electrochemical, thermal or photo/
photo-biochemical process.24–29 In either of the cases, the over-
all selectivity, efficiency and sustainability of the process
depends upon the reaction conditions and the nature of the
photocatalyst. The natural way of photo-biochemical reduction
of CO2 is the most preferred way of selectively and efficiently
reducing CO2. The efficiency of the photo-biochemical process
majorly depends upon the regeneration of co-factor 1,4-NAD(P)
H which is also of signicant importance for numerous other
biotransformation reactions.27 In quest of developing photo-
catalyst for repeat cycles for NADH regeneration, we scanned all
the four PTF photocatalyst for NADH regeneration (Fig. 5a). A 1
ꢃ 3 cm2 dimension of the PTF thin lm layered on polyimide
substrate was used as order of 53.65%, 98.75%, 35.25% and
25.36% in two hours of visible light illumination for PTF-1min,
PTF-15min, PTF-1h and PTF-12h respectively. The trend of
formic acid production was in correlation to the NADH regen-
eration performance (Fig. S7, ESI†). The order of formic acid
formation was 187.25 mmol, 334.1 mmol, 125.69 mmol and 73.25
mmol in two hours of illumination for PTF-1min, PTF-15min,
PTF-1h and PTF-12h respectively (Fig. 5b).
Encouraged by the excellent photo-electronic properties of
PTF thin lm, we evaluated its ability to photocatalyze visible-
light-driven reductive dehalogenation of a-bromoacetophe-
nones. The reductive dehalogenation of a-bromoacetophe-
nones is an important reaction widely utilized for the synthesis
of various drug molecules (Scheme S3, ESI†).21–23 The photo-
catalysis was carried in a quartz reactor under an inert atmo-
sphere at room temperature, using solar stimulator stimulated
@AM 1.5, 1 Sun, (Newport Instruments, USA) as light source.
The reductive dehalogenation of a-bromoacetophenones to
acetophenones was performed in presence of Hantzsch ester
and DIEPA in acetonitrile. a-Bromoacetophenone was used as
substrate to optimize visible-light-driven reductive dehaloge-
nation using PTF thin lm as photocatalyst (Table S4, ESI†). The
reaction failed in the absence of either a photocatalyst (entry no.
2, Table S4, ESI†) or light (entry no. 3, Table S4, ESI†), as ex-
pected for
a photocatalytic reaction. Neither satisfactory
conversion occurred in absence of either Hantzsch ester light
(entry no. 4, Table S4, ESI†) or DIEPA light (entry no. 5, Table S4,
ESI†). The photocatalysis occurred efficiently in polar solvents,
and best conversion was obtained in acetonitrile. The photo-
catalysis exhibited wide substrate scope for various a-bromoa-
cetophenones (Fig. 4). The favourable band edge positions of
the PTF photocatalyst led to facile single electron transfer to a-
bromoacetophenones upon visible light illumination
producing acetophenones under mild, reaction conditions. The
In order to conrm the trend of photocatalytic activity for
CO2 to formic acid formation, CO2 adsorption properties for all
the four PTF photocatalyst were also measured. The CO2
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Fig. 5 (a) Photochemical NADH regeneration (b) formic acid production. The NADH regeneration was carried out using 1 ꢃ 3 cm2 film pho-
tocatalyst by illuminating the quartz reactor containing b-NAD+ (1.24 mmol), rhodium complex, Rh (0.62 mmol) and ascorbic acid (0.1 mmol) in
3.1 mL of 0.1 M sodium phosphate (NaH2PO4–Na2HPO4) buffer (pH ꢂ 7.0). A solar stimulator stimulated @AM 1.5, 1 Sun, (Newport Instruments,
USA) was used as a light source. Similar reaction conditions were followed for CO2 photoreduction in presence of 3U FDH. (c) Control reactions
carried out under standard conditions varying different factors in the PTF photocatalyst–biocatalyst coupled system.
adsorption isotherms obtained of all the four PTF photocatalyst photocatalysis was examined via FESEM and FTIR studies. The
(Fig. S8, ESI†), were in correlation to their photocatalytic effi- FESEM image of the PTF-15min photocatalyst aer six repeat
ciency with PTF-15min displaying highest adsorption capacity.30 cycles of photocatalysis displayed presence of continuous thin
Enhanced CO2 adsorption is also an essentially requirement for lm surface with negligible corrosion (Fig. S10, ESI†). The FTIR
further boost CO2 photoreduction reaction.31,32 Overall, all these spectra also displayed similarity in their transmittance pattern
results support the enhanced photoelectronic and surface before and aer repeat cycles of photocatalysis (Fig. S11, ESI†).
properties of the PTF-15min as a photocatalyst for CO2 The enhanced stability and efficient photocatalytic activity of
photoreduction.
PTF-15min could be due to its efficient electron–hole pair
The PTF-15min was screened for repeat cycles of NADH generation ability with enhanced charge separation under illu-
regeneration (Fig. S9a, ESI†) and formic acid formation mination. A comparison of literature survey for CO2 to formic
(Fig. S9b, ESI†) and a minimal loss of photocatalytic activity was acid conversion via photocatalytic–biocatalytic integrated
evident. The stability of the photocatalyst aer six cycles of system is presented in Table S6, ESI† where our proposed work
Scheme 2 Graphical illustration of PTF photocatalyst–biocatalyst coupled system for selective formic acid production from CO2 under visible
light illumination. NAD+ ¼ nicotinamide adenine dinucleotide and FDH ¼ formate dehydrogenase.
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comparatively shows enhanced photocatalytic activity with within two hours of visible light illumination. Besides excellent
robust recyclability. photocatalytic activity, the excellent recyclability of the PTF
A schematic illustration of the photocatalyst–biocatalyst photocatalyst opens a new avenue for design and fabrication of
integrated articial photosynthesis system for formic acid advanced applications but also provides an inspiration easy
production from CO2 is depicted in Scheme 2. The PTF photo- fabrication of multi-functional thin lms for biological and
catalyst actively harvests incident visible light as electronic wearable devices.
transition between its HOMO and LUMO orbitals (Eg ¼ 2.4 eV)
upon visible light illumination. The favourable energy level of
Author contributions
the conduction band in the PTF photocatalyst render electrons
to the rhodium complex Rh([Cp*Rh(bpy)H2O]2+; Cp* ¼ pen-
D. Y. and J. O. B. designed the project. D. Y., A. K. and J. O. B.
prepared the manuscript. D.Y. prepared the photocatalyst and
performed analysis and photocatalytic applications. All authors
contributed to the results discussions and manuscript revision.
tamethylcyclopentadienyl, bpy ¼ 2,20-bipyridine) upon visible
light excitation. The reduced Rh complex then abstracts
a proton from water and transfers the hydride ion to NAD+
reducing it to NADH, which completes the photocatalytic
cycle.33 The cyclic voltammetry studies were performed to confer
Conflicts of interest
the light-induced electron transfer mechanism from PTF pho-
tocatalyst to Rh complex and NAD+.34 The PTF photocatalyst and
There are no conicts to declare.
Rh complex shows an increase in the cathodic peak current with
a potential shi in presence of NAD+ (Fig. S12, ESI†), indicating
the electron transfer from PTF photocatalyst and Rh complex to
Acknowledgements
NAD+. The so formed NADH is consumed by formate dehydro-
This work was supported by “Next Generation Carbon Upcycling
Project” (Project no. 2017M1A2A2046736) through the National
Research Foundation funded by the Ministry of Science and
genase enzyme (FDH) for the conversion of CO2 to formic acid.
The NAD+ is released back into the photoreaction which again
acts as a substrate for photocatalytic NADH regeneration. The
ICT, Republic of Korea and KRICT grant number: KRICT
photocatalytic and enzymatic cycles thus combine to exclusively
produce formic acid from CO2.
(SI2161-21).
Furthermore, few essential control experiments were also
carried out varying any one factor involved in photocatalysis. In
either of the cases, no formic acid was detected via ion chro-
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corresponding to H13COOH (Fig. S13, ESI†). This proved that
the formic acid was produced from CO2 by the PTF photo-
catalyst–biocatalyst integrated articial photosynthetic system
under visible light.
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Conclusions
Conclusively, the pressing need for the development of a robust
and efficient photocatalyst for continuous photocatalysis is well
achieved. A simple, scalable, reagent free synthesis of a robust,
freestanding lm based COF photocatalyst has been estab-
lished via interfacial synthesis. The results showed that the
optical properties and efficiency of PTF photocatalyst can be
tuned for visible-light-induced solar fuel production utilizing
carbon dioxide via controlled interfacial synthesis. Tuning the
concentration and interfacial reaction time, the thickness of the
lm could be controlled which had a signicant impact on the
photocatalytic activity of the PTF photocatalyst. As depicted, in
Scheme S2 in ESI,† the optimum band edge positions, suitable
band gap, greater charge generation ability (15 times) along
with enhanced lifetime endows the PTF-15min photocatalyst
with superior photocatalytic ability. The PTF-15min photo-
catalyst shows highly enhanced visible light driven 1,4-NADH
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