## 1 Introduction  
Environmental pollution is increasing all over the world due to population growth and industrial development. Dyes are considered one of the leading pollutants, and they have every chance of affecting the surrounding environment in several ways [1]. They have a profound and lasting effect on exposed animals, depending on the concentration and duration of exposure, stimulating the evolution of bacteria that interfere with photosynthesis, absorbing and reflecting light from incoming water, and preventing the growth of aquatic plants [2]. In addition, dyes are used in the food industry to improve the appearance, smell, taste, color, texture, calorie content and shelf life of food. Most dyes are considered mutagenic and carcinogenic due to the presence of aromatic rings in their structure. The presence in food and the appearance of these dyes in surface and groundwater are considered unsafe for human well-being. High doses can cause a variety of health problems, including allergic reactions, skin irritation, gastrointestinal problems, and overactivity in children. Consequently, the presence of dyes in foods is highly regulated, and scientists are developing simple and inexpensive methods for detecting and extracting dyes to minimize their contamination of wastewater. The problem of detecting and identifying the content of organic dyes in food products is relevant, and, therefore, various methods are used for this purpose, including UV spectrophotometry, high-performance liquid chromatography, spectrofluorometry, electrochemical voltammetry, and mass spectrometry [3; 4; 5; 6; 7; 8; 9; 10; 11; 12; 13; 14]. However, when determining the concentration of the dye, various limitations and obstacles are observed, such as the low concentration of the dye in food samples, which cannot be detected using instruments, and the positive or negative interference effect of the matrix components. Because of this, the concentrations of dyes in foods cannot be accurately determined. Therefore, separation and pre-concentration methods are needed. There are several methods most suitable for the extraction, separation, and concentration of dyes. One of them is the solid-phase extraction (SPE) method. This method is common and is used to isolate and concentrate synthetic food colorings. Metal-organic frameworks (MOFs), which are used as sorbents in the SPE method, are new porous compounds, which are also called hybrid porous coordination polymers [15]. MOFs are types of adsorbents that exhibit unique physical and chemical properties by combining metal-containing units with organic linkers, using strong bonds to create open crystalline frameworks with a constant porosity [16; 17; 18; 19; 20; 21; 22; 23]. A consistent porosity, low density, high surface area, suitable pore size, metal node functionality, and structural flexibility make MOFs unique and well suited for a wide range of applications. In addition, the high surface area and porosity of MOFs can facilitate the diffusion of contaminants through the framework and the presence of an adsorption site. Thus, MOFs are among the most suitable structures in the field of adsorption and separation [24; 25; 26; 27]. The terephthalate ion is used as a ligand in MOF chemistry because functional groups in the para-position contribute to the formation of polymer chains that form both monometallic and heterometallic two- or three-dimensional coordination compounds. Based on the possibilities of the structure of the terephthalate ion, it can be assumed that it can function as a bi-, tri-, or tetra-detate ligand [28]. For example, copper terephthalate exhibits a high adsorption capacity with respect to various dyes and metal ions [29; 30; 31; 32]. An important task today is the study and development of simple and efficient methods for the synthesis of these compounds. The aim of this study was to develop a simple sorption-spectrophotometric method for the determination of food additives using MOF based on copper terephthalate as an adsorbent.