Urbanization and economic development result in the problems due to extensive use of nitroaromatic compounds (NACs), toxic gases, heavy metal ions and pollutants. Security-terrorism and crime scene investigations are the areas of special concern dependent on explosive detection. Increase in the incidences of terrorist bomb attacks and overuse of land mines have become an alarming threat to human life . Consequently, for the security of human life, these NACs must be detected without any delay with the simple possible methods. There are various technologies available for their detection like gas chromatography-mass spectrometry (GC-MS), liquid chromatography-mass spectrometry (LC-MS), energy dispersive X-ray spectroscopy (EDS), surface enhanced Raman spectroscopy (SERS), high-performance liquid chromatography (HPLC), electron capture detection (ECD), proton transfer reaction mass spectrometry (PTR-MS), nuclear quadrupole resonance (NQR), neutron activation analysis (NAA) and ion mobility spectrometry [2–4], but all these techniques are highly sensitive, expensive and require highly sophisticated instrumentation with further need of some special type of training . Hence, these techniques cannot be utilized for on-site field testing. Instead, fluorescence-quenching-based chemical detection proved to be a simple, sensitive, rapid and less expensive method for the quick detection of nitroaromatic compounds. It needs a fluorescent material with simple mechanism of detection via transmission of the signal in the form of charge between sensing material and the analyte . Detection of nitroaromatic compounds, heavy metal ions, toxic gases and pollutants, are the major areas covered recently by chemical sensors based on porous MOFs. Nitroaromatic compounds are causing problems for human health and environment, among NACs 4-nitroaniline (4-NA) causes serious problems not only to aquatic organisms, but also to human health due to its accumulation in waste water. 4-NA is widely used as precursor in chemical synthesis of dyes, pesticides, poultry medicines, fuel additives, antiseptic agents, and important corrosion inhibitors . It proves to be lethal for human health by causing various serious problems to human health including diarrhea, liver injury, skin eczema, respiratory arrest, methemoglobinemia, and anemia . Due to its high persistence, biodegradability and chemical stability, it can cause long term environment damage . Many developed and developing countries levied restriction on its production, usage and disposal and added it into the list of major pollutants . Really, there is a need to establish rapid, selective and sensitive method for the detection of 4-NA. Currently, fluorescence sensing has been utilized on a large scale in chemistry, biology and environmental science [7–9]. Affordability, stability, quick response, simplicity, easy operation and availability of fluorescent sensors has created an interest among researchers to work in this field.
High sensitivity and low limit of detection (LOD) are the major concerns of an explosive sensor with additional high selectivity to avoid false signals. The vital class of explosives include nitroaromatic compounds. These materials have very low vapour pressure making them suitable for attachment on the high surface energy surfaces such as metals and metal oxides as compared to polymers, plastics etc. Moreover, the interaction between analyte and sensor material gets enhanced by increasing surface to volume ratio, quantum size effects and porosity . Fluorescence sensors work on the principle of luminescence quenching or augmentation caused by the interaction between analyte and sensing material. This alteration in luminescence is caused due to the following reasons: (a) Crystal structure damage, (b) Exchange of cations between central cation of sensor and the targeted cations, and (c) Interaction between the NACs and sensor, which results in adsorption competition and resonance energy transfer .
Many industries like textile, plastic, leather and cosmetics consume large amount of water and produce coloured effluents. More than 700000 hazardous dyes from various industries are directly discharged into water bodies without any treatment, which cause serious water pollution. These materials have serious environmental and human health issues due to their carcinogenic and toxic effects [12, 13]. So, as a remedy of these industrial effluents various methods have been utilized like adsorption of dyes on high surface area support, sedimentation, chemical coprecipitation, ion exchange method and use of biological membranes . However, these methods are not preferred to a large extent due to their expensive equipments, time consuming processes and conversion of main pollutant into secondary pollutants, which needs further removal. Biochemical and physiochemical methods are not suitable for decolourisation of dyes from industries due to their inflexibility towards chemical oxidation and photocatalytic stability. Moreover, researchers are also interested to utilize MOFs for the purpose of water purification and remediation of water through their potential photocatalytic activity for the degradation of dyes in water.
Therefore, there is a need of such materials, which can act both photocatalyst as well as sensor for detection of nitroaromatic compounds. The advanced oxidation process and moderate reaction conditions make Metal Organic Frameworks (MOFs) an interesting topic of the current research. MOFs are hybrid of organic linkers with metal ions/clusters, which are interconnected to form 2D or 3D porous structures . Compared to inorganic semiconductors, MOFs have open metal sites, unsaturated metal centers and catalytically active linkers as a main advantage. These are rapidly developing due to their large surface areas, rich active sites, diverse structural topologies and various potential applications, such as gas storage , separation , heterogenous catalysis , sensing , photocatalytic activity  and so on.
Several routes have been proposed for the synthesis of MOFs like diffusion, hydrothermal /solvothermal methods , which require high temperature and pressure for operation. In recent years, some faster routes like sonochemical , mechanosynthesis  and microwave  have been introduced. But these have some disadventages like high energy consumption, complex process, requirement of advanced equipment, introduction of unwanted anions with the use of metal salts, long reaction time and difficulty in regulation [22, 23]. So, for the advancement of the field a mild and clean synthesis method for the purpose of overcoming the mentioned disadvantages is required. So, there are few reports on electrochemical synthesis which is facile and environment friendly with advantages including mild reaction conditions, simple operation and cleaning process. Moreover, metal ions are produced through anodic oxidation which avoids the problematic anions such as nitrates from metal salts. In electrochemical method size and morphology can be optimized by different factors like nature of solvent, applied current, electrolyte concentration, electrodeposition time and distance between counter electrodes . Protic solvent like water ( green and economic) opted as a solvent and copper metal electrodes are employed instead of costlier platinum or titanium electrodes. Electrolysis have been carried out under amperostatic conditions.In the present work, Cu (II) based MOF [Cu3(BTC)2] has been synthesized using facile electrochemical method. Cu3(BTC)2 shows a hydrogen bonding, which results in its three-dimensional supramolecular framework. Synthesized MOF has been characterized by various characterization techniques such as FT-IR, Powder-XRD, SEM, EDS, UV-Vis. absorption spectroscopy and photoluminescence spectroscopy to explore their potential for NACs sensing and photocatalytic applications. To the best of our knowledge, Cu3(BTC)2 has been reported first time to act as a good and efficient luminescent sensor for these particular NACs: 4-NA, 2-NA, 3-NA, 4-NT, 2,4-DNT, 1,3-DNB, 2,6-DNT with selectivity towards 4-NA showing quenching efficiency and LOD to be 82.61% and 0.7544ppb, respectively. Additionally, based on the characteristics of Cu3(BTC)2, it has been utilized first time for photocatalytic activity towards degradation of MB dye as a test aqueous contaiminant, which showed virtuous photocatalytic activity for green degradation of MB.