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Catching molecules and nanoparticles from liquid media is a timely research topic because of the many practical applications dealing with the protection of the environment and the sustainability of chemical processes and products in general. Although substantial scientific progress has already been made, many scientific challenges remain. Recovery of dissolved catalysts and trapping of suspended catalyst particles are critical operations in many catalytic processes. Residual catalyst is undesired because it represents an impurity often involving transition metals and may show uncontrolled residual catalytic activity. Trapping of dissolved or suspended nanoparticles preferentially should occur on a macroscopic support having preferentially a porous structure to maximize capacity. In an ideal scenario the catalyst should be quantitatively recovered, and be reusable through controlled liberation from the support in a new reagent batch. Uncontrolled leaching and limited recyclability can be problematic in catalysis in aqueous phase in which transition metals are soluble. Current approaches are mostly based on permanent catalyst heterogenization. In the first part of this work new strategies were explored to trap homogeneous polyoxometalates catalysts. Polyoxometalates (POMs) are known to be excellent acid and redox catalysts. Their recovery after reaction remains a challenge as they are soluble in both aqueous and organic media. Polyoxometalates are expensive and often toxic, which makes recovery and reuse essential. We took profit of the solvent dependent solubility of Cu3(BTC)2 metal-organic framework (MOF) to immobilize POMs by encapsulation and to release them at will by changing solvent. The release of POM catalyst from Cu3(BTC)2 MOF and POM recovery by encapsulation was demonstrated in esterification reactions.The trapping of pollutant molecules in water bears some resemblance with catalyst recovery, since both species are present in small amounts. The elimination of undesired molecules in the area of water purification is a challenge since these pollutants are often present in minute quantities at parts per billion (ppb) or even parts per trillion (ppt) level and still present an environmental problem. Many techniques have been investigated to eliminate organic molecules form water, such as membrane-filtration, adsorption, advanced oxidation processes, chemical treatment, and bio-degradation. Generally, these techniques are less efficient for eliminating compounds at sub ppm concentration level. Geosmin is such a problematic compound responsible for earth muddy taste and smell even at ppt concentration. It is a natural compound produced by microorganisms, and it problematic in drinking water and in aquaculture. In aquaculture the quick adsorption of geosmin into lipid-rich tissue of fish is problematic. Dedicated analytical methods are needed for experimentation at ppt concentration levels. In this work headspace solid phase micro extraction (HSPME) in combination with GC-MS was used to quantify geosmin concentrations in the 1 to 100 ppt range. Photocatalytic destruction using suspended TiO2 semiconductor nanoparticles and TiO2 films on walls of water vessels is an option for eliminating geosmin from water, but it suffers from slow reaction kinetics, leading to inefficient use of UV light and photocatalyst. In the second part of this work the use of zeolite adsorbents to enhance the geosmin concentration in the vicinity of the photocatalyst is investigated. Synergy of TiO2 photocatalyst particles and zeolites in coatings are efficient especially in the ppt range typical of aquaculture water. Geosmin is an expensive chemical. The much cheaper 1-adamantanol behaves like geosmin in photocatalytic degradation and is proposed as a geosmin mimic.