**1. Introduction**

A growing focus on heterogeneous catalysts has emerged in recent years due to economic and environmental factors. These catalysts typically have low cost, high reactivity, environmental friendliness, high selectivity, easy setup, and recoverability of catalysts [1]. Mesoporous MCM-41 materials have come to light as highly stable compounds with a significant surface area. They have been widely used as catalysts or catalyst supports in a variety of processes. This was explained by the reaction

mixture's higher reusability and straightforward recoverability [2]. Due to their increased oxidative or acidic character, the introduction of metal ions including Ti4+, Al3+, Co3+, and Fe3+ into the framework has demonstrated improved catalytic activity [3].

Due to contaminated ground water and dangerous industrial effluents, the entire world is currently experiencing environmental issues [4, 5]. These highly coloured effluents harm the environment when they are dumped into water systems because they impede light penetration and hinder aquatic life's ability to photosynthesize [6, 7]. Intense colour is imparted by the presence of dyes in the effluent at very low concentrations (1 mg L<sup>1</sup> ) but it is discovered that they are harmful to the environment [8, 9]. In order to effectively remove colour from waste fluids, physical or chemical procedures must be used [10]. The majority of dyes used on an industrial basis are derivatives of azo, anthraquinone, indigo, triphenylmethane, xanthene, and others [11, 12]. Due to their advantageous qualities—bright colour, easy application, and low energy consumption—these dyes are widely utilised in the textile industry. They are, however, typically the most poisonous and mutagenic substances found in nature [13, 14].

One of the anthraquinone class of dyes, Alizarin Red S (ARS), is widely used in the textile, woven fabric, wool, and cotton industries [15–17]. The paint, plastics, leather, and cosmetics sectors all utilise anionic dye extensively [18]. However, when industrial effluents are released into aquatic environments at amounts exceeding what is permitted, the aquatic life is negatively impacted [19, 20]. It was shown that traditional aerobic digestion techniques were ineffective at degrading these resistant compounds [21]. Photo catalysis has become a green technique for gathering solar energy and degrading organic pollutants due to the global energy crisis and environmental challenges [22–25]. ARS was selected as the test molecule to undergo photodegradation in the presence of visible light as a result.

MCM-41 and its metal-included derivatives have a wide range of photocatalytic uses, so cobalt metal ion (Co+3) was successfully inserted into the structure of MCM-41. In order to research the photodegradation of ARS under ideal experimental settings, such as effect of photocatalyst, effect of photocatalyst dose, effect of dye concentration, and effect of pH, the materials were characterised and used as photocatalysts. To identify the active species participating in the photodegradation phenomenon, a scavenger experiment was done in addition to these research. To assess how well the outcomes matched each other, the kinetic research was carried out.
