This document summarizes research on synthesizing a transition metal-based Metal-Organic Framework (MOF) for sensor applications. Key points: - A zinc-based MOF was synthesized using terephthalic acid as the organic linker through a solvothermal method. - Characterization with XRD, FTIR, UV-VIS and photoluminescence showed the MOF had a crystalline structure with pores and displayed dynamic luminescent properties essential for chemical sensing. - The MOF exhibited red-shifted fluorescence compared to the free linker molecule, indicating coordination interaction between the zinc and linker affected its luminescence.

1. A dynamic luminescent transition metal based Metal-Organic Framework
(MOF) for sensor application
Abhishek Katoch1, Richa Bhardwaj2, Navdeep Goyal2 and Sanjeev Gautam1,*
1Dr. S.S. Bhatnagar University Institute of Chemical Engineering & Technology, Panjab University, Chandigarh – 160 014, India
2Department of Physics, Panjab University, Chandigarh – 160 014, India
Fig. 1. Summary of PXRD patterns of Zn-(BDC) MOFs in
comparison with graph obtained by poonam et.al (RSC Adv., 2015,5,
28270).
Figure 2. Optical measurements were performed by UV-VIS
spectroscopy. Band gap was calculated using Tauc-plot and
came around 3.9eV.
Figure 3. FTIR analysis showed the presence of all the
functional groups present inside the sample.
References
1. Bradshaw et. al. Chem. Soc. Rev. 2014, 43, 5431-5443.
2. Omar M yaghi et. al. Nature volume423, pages705–714
3. U. Mueller et. al. J. Mater. Chem., 2006,16, 626-636
4. N. Iswarya et. Al. , Asian J. Sci. Res., 5: 247-254.
5. Javier roales et. al. Materials 2017, 10(9), 992;
6. ColinMcKinstry et. al. Chemical Engineering Journal
Volume 285, 1 February 2016, Pages 718-725
Acknowledgments
1.This research was conducted in the Chemical Engineering
Department at the Panjab University Chandigarh. TEQIP-III
grants are acknowledged.
2.Co-researcher and Support staff (Mr. Sethi) in applied Physics
laboratory are duly acknowledged.
Metal organic Framework (MOF) are 3D materials with high
crystallinity, where metal ions are coordinated to polydentate organic
linkers. The limited conductivity of the MOF inhibits their applications
as sensor, so our approach here is to enhance the sensing properties of
prepared MOF sample [1, 2]. In this research work, transition metal
(Zinc, Copper, Cobalt) based MOF is synthesised by solvothermal
technique. The prepared MOF sample consist of Zn4O, which is
coordinated to BDC (Terephthalic acid) as precursor, dissolved
individually in DMF(dimethyle formamide). The excess water
molecules are removed using DEA (diethanol-ammine), while reaction
energy is provided by citric/malonic acid. A detailed synthesis route and
mechanism, with systematic characterization (X-ray diffraction, thermal
analysis, SEM/EDX) is reported in this paper. Surface morphology
showed well-ordered structure with large number pores in mesoscale.
Photoluminescence/fluorescence measurements revealed the dynamic
luminescence properties of the synthesised MOF essential for chemical
sensor applications [2].
Background
 Rigid, crystalline, porous and non interpenetrating Structure
with organic ligands to metal centers.1
 Applications include gas storage, molecular separation,
catalysis, sensing, and drug delivery. They are known to have
high porosities, tunable pore size, structures, and functionality.
 Many dicarboxylic acids (i.e. oxalic acid, malonic acid,
succinic acid, glutaric acid, terepthalic acid), tricarboxylix acid
(i.e. citric acid, trimesic acid) or azoles (i.e. 1,2,3-triazole,
pyrrodiazole) are used as a linker.
 Due to vast availability of metal-ligands combinations MOFs
has been studied as the wide area of research.
Basic properties of Metal-organic frameworks
 Gas storage
 Gas separation, Gas adsorption, Gas purification.
 Catalysis
 Hydrogen storage, Methane storage, Carbon dioxide
storage.
Functional group
stretch
Frequency
(cm-1)
Observed Value
(cm-1)
Alkane C-H bending 1350-1480 1375
Aromatic C-H bend 675-870 743
C-H group in plane
bending
1225-950 1014
1114
ZN-O stretching Around 500 527
Table 1. Table representing the values of various
functional groups and their values.
Discussions
For any suggestions/queries contacts Email ID akatoch61@gmail.com
 During the cooling of mixture there is large energy penalty,
we need energy efficient method to separate
them.( frequently air/moisture-sensitive)
 Many issues and controversies remain about the nature
of the experimentally observed MOFs
• Low electrical conductivity of most MOFs therefore their
use as a electronic sensor devices has become limited.
• So our approach here will be to develop a sensor which don’t
get erode away or get affected by foreign particles and
should be helpful in fast and accurate sensing.
• We will optimize the sample at various temperatures.
Origin of problem
 FTIR spectra confirm the presence of all the functional
groups present in MOF.
 Fluorescent spectra were measured at room temperature
with Fluorescence Spectrophotometer. the solid-state
luminescent properties of H2BDC and the
complexes were investigated at room temperature.
 While the maximum of luminescence band of the free
H2BDC in the solid state appears at 392 nm, which is
probably due to the intraligand π → π* transition,
 MOF-5 shows emission band at λmax= 446 nm. The
visible red shift for such fluorescence peak, compared to
that of free H2BDC ligand, is the result of Zn(II)–H2BDC
ligand coordination interaction (d-L).
 photoluminescence studies are important to understand
the charge-transfer pathways and the various studies
pointed out the observation of three types of luminescent
behavior: i) intra-ligand luminescence, ii) ligand to metal
charge transfer (LMCT), and iii) ligand sensitized metal
center luminescence.
• The crystalline size calculated using De-bye Scherer
formula (D=Kλ/(βcosθ) where λ is X-ray wavelength, D is
size of crystallites size, B is full width half maximum, θ is
Bragg’s angle, K is constant.
• The crystallite size comes around 38.89nm at 9.080,
37.09nm at 10.160, 50.94nm at 5.360.
• The X-Ray diffractograms correspond with that of the
pattern obtained by (Poonam rani et al.). It is evident from
the diffractograms that sample is crystalline in nature.
Figure 4. Excitation spectra of Zn(BDC)-MOF in solid state at room
temperature
Methods
As the crystallinity of the MOF increased, the yield was
reduced(residence time during heating). For Zn(BDC) MOFS,
the ratio with the greatest crystallinity displayed the best yields.
Modulated Solvothermal Synthesis of MOFs
• Zn(NO)2•6H2O, terepthalic acid, diaethanolamine and citric acid
were individually dissolved in DMF and mixed after
continuous stirring.
• Heated at 1600c for 48hours to yield a white powder.
• Residual reagents were removed by fresh Dmf washing.
• Dried the Sample at 800c for 48hours
Characterization
For MOF samples following are done
• X-ray diffraction, UV-DRS
• FTIR
• Fluorescence spectroscopy
UV-VIS
FTIR Photoluminescence
Hydrothermal Autoclave
Abstract
XRD