The scarcity of clean water becomes an urgent problem that we are facing. Moreover, most of the conventional water purification technologies are energy-intensive, expensive, and not environmentally friendly. As a result, the material that efficiently absorbs light and converts it to heat to generate water vapor has to be developed. Consequently, the overall objective of this research was to develop efficient photothermal material from waste coffee grounds for water purification. High carbon content and good solar light absorber property, easily and cheaply availableness of coffee grounds were the main reasons to select it as the raw material of this research. The waste coffee grounds were activated using chemical activation to develop a wide range of solar spectrum absorption. Hydrophilic surface modification and floating system design parameters of photothermal material were employed to improve the water supply and thermal management of the material respectively. An activated coffee-based photothermal layer capable of generating vapor at a high rate of 1.12 kg m -2 h -1 under 980Wm -2 irradiation was prepared by the vacuum filtration method. The photothermal conversion efficiency of 74.5% was achieved. The solar transparent glass was designed and constructed to collect the purified water by vaporization. Sample water for purification was taken from the lakeshore of Tana at Bahir Dar city. Sample sites for sample water collection were selected purposively. The level of Cu +2 ion concentration, turbidity, TDS, microbial load, and total hardness sharply decreased in the purified water. Thus, depending on the purpose of water purification and by doing the required water quality analysis, the purified water can have the potential to be used in different applications. The result has shown that the prepared photothermal layer exhibited good performance for water purification using sunlight irradiation. Easy preparation, availability, environmental acceptance, reusability, and well solar evaporation performance will contribute to the promising potential of using waste coffee grounds in future steps toward eco-friendly water purification procedures.