DOI: 10.1002/cctc.201501352
Communications
Sustainable Strategy Utilizing Biomass: Visible-Light-
Mediated Synthesis of g-Valerolactone
Sanny Verma+,[a] R. B. Nasir Baig+,[a] Mallikarjuna N. Nadagouda,[b] and Rajender S. Varma*[a]
A novel sustainable approach to valued g-valerolactone was in-
vestigated. This approach exploits the visible-light-mediated
conversion of biomass-derived levulinic acid by using a bimetal-
lic catalyst on a graphitic carbon nitride, AgPd@g-C3N4.
The growing energy demand and its impact on the environ-
mental system are leading to climate change, and ensuing
consequences are now widely visible in the surroundings.
World leaders have realized the importance of environmental
protection, and efforts are being made to address this chal-
lenge with utmost urgency.[1] One of the major reasons for the
Figure 1. g-Valerolactone (GVL) and its application as an organic precursor.
environmental imbalance is the growing consumption of fossil
fuels and our continued dependence on petroleum products,
which are responsible for irreversible damage to the environ-
ment and living beings. Efforts have been made to have a para-
bolic shift towards biomass-derived chemicals as a feedstock
to replace petroleum-based products.[2] Extensive research is
being pursued to convert biomass-derived precursors into
value-added chemicals that can be used as biofuels and inter-
mediates in the synthesis of pharmaceutically and industrially
important products.[3]
mixture at 2008C in a specialized autoclave apparatus under
high hydrogen pressure.[6] In view of the safety concerns in the
hydrogenation step, biomass-accessible formic acid has been
introduced as an alternative for the synthesis of GVL, although
prolonged heating at elevated temperatures still remains
a main shortcoming of these methods.[7]
Despite the many limitations of reported protocols,[8] the uti-
lization of visible light has not been exploited to accomplish
this transformation. Engaged in an ongoing program to devel-
op benign and sustainable methods in organic synthesis,[9]
herein, we report an ecofriendly protocol for the synthesis of
GVL by using a photoactive bimetallic AgPd@g-C3N4 catalyst.
Graphitic carbon nitride (g-C3N4) was synthesized by calcina-
tion of urea at 5008C in a heating furnace. g-C3N4 was isolated
as a porous pale yellow solid immediately after calcination in
pure form.[10] An aqueous suspension of g-C3N4 was prepared
by dispersing g-C3N4 in water under sonication. The AgNO3
and Pd(NO3)2 salts were added simultaneously to the suspen-
sion of g-C3N4, and the mixture was stirred overnight. The reac-
tion temperature was elevated to 508C, and the silver and pal-
ladium metals were reduced by using an excess amount of
sodium borohydride (NaBH4). After the reduction, the reaction
temperature was reduced to ambient temperature. The mix-
ture was centrifuged, and the AgPd@g-C3N4 catalyst was isolat-
ed as an off-black solid (Figure 2).
g-Valerolactone (GVL) is an important molecule that can be
accessed from biomass resources[4] and converted into many
important scaffolds,[5a] namely, the antihypertensive drug
WS75624,[5b] the anticancer drug Steganacin,[5c] the insecticide
agrochemical Geodiamolide,[5d] the aggregation pheromone
Sulcatol,[5e] jet fuel[5f] (Figure 1), and many other important or-
ganic products used in the treatment of disease crop protec-
tion; it is also an alternative source of green energy.[4,5] Because
of its wider application in chemical industries, researchers have
been searching for sustainable methods to produce GVL from
biomass. An often-used pathway entails heating levulinic acid
under high hydrogen pressure. Recently, a nanoalloy was uti-
lized to convert levulinic acid into GVL by heating the reaction
[a] Dr. S. Verma,+ Dr. R. B. N. Baig,+ Dr. R. S. Varma
Sustainable Technology Division
National Risk Management Research Laboratory
U. S. Environmental Protection Agency
MS 443, Cincinnati, Ohio 45268 (USA)
Fax: (+1)513-569-7677
The AgPd@g-C3N4 catalyst was characterized by scanning
electron microscopy (SEM), transmission electron microscopy
(TEM), X-ray photoelectron microscopy (XPS), and X-ray diffrac-
tion (XRD). The surface area was analyzed by using Brunauer–
Emmett–Teller (BET) analysis. The metal percentage was deter-
mined by inductively coupled plasma atomic emission spec-
troscopy (ICP-AES).
E-mail: varma.rajender@epa.gov
[b] Dr. M. N. Nadagouda
WQMB, WSWRD, National Risk Management Research Laboratory
U. S. Environmental Protection Agency
MS 443, Cincinnati, Ohio 45268 (USA)
[+] These authors contributed equally to this work.
The SEM images of graphitic carbon nitride (g-C3N4) and the
AgPd@g-C3N4 catalyst confirm immobilization of silver (Ag) and
palladium (Pd) nanoparticles over the g-C3N4 support
Supporting Information and ORCID(s) from the author(s) for this article
ChemCatChem 2016, 8, 690 – 693
690
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim