## 1 Introduction  
The depletion of fossil resources and urgent environmental challenges have accelerated the shift toward renewable biomass as a sustainable feedstock for producing high-value chemicals, materials and fuels [1, 2, 3, 4]. Indeed, in line with green chemistry principles, biomass valorization aims to reduce waste, minimize energy consumption and mitigate environmental impacts [5, 6]. Among its key transformations, the oxidation of biomass-derived molecules offers routes to fine chemicals for pharmaceuticals, polymers and agrochemicals [7]. In this context, terpenes--as one part of the biomass--are a relevant renewable source for the production of high-value derivatives [8]. This study focuses on two representative terpenes, \(\beta\)-myrcene and \(\beta\)-caryophyllene (Figure 1), chosen for their availability and applications. \(\beta\)-myrcene is an open-chain monoterpene derived from natural sources [9] or via \(\beta\)-pinene pyrolysis [10]. Its oxidation product, myrcene oxide, is a key intermediate for industrial applications and as an intermediate in the synthesis of fine chemicals, particularly in flavor and fragrance industries [11], as well as in polymer chemistry, enabling the synthesis of bio-based polymers through its reactive epoxide group [10, 12, 13, 14, 15, 16, 17, 18, 19]. On the other hand, \(\beta\)-caryophyllene, obtained from several sources in essential oils [20], is known for its unique bicyclic structure and biological activity [21, 22]. Its oxidation yields \(\beta\)-caryophyllene oxide, a compound of high commercial interest due to its use in fragrances,cosmetics and pharmaceuticals [22; 23; 24; 25], as well as its anti-inflammatory, antimicrobial and anticancer properties [26; 27; 28]. Prior oxidation methods for these two terpen often relied on harsh and non-sustainable conditions. These included toxic oxidants such as chromium(VI) reagents [29], \(m\)-chloroperbenzoic acid (mCPBA) [18; 19; 30; 31] and even oxone [25; 32; 33; 34]; most of these processes used hazardous chlorinated solvents such as dichloromethane and chloroform. Additionally, many of these protocols employ expensive and unrecyclable metal-based homogeneous catalysts based on Cu coordination polymers and MOFs [35; 36; 37], MeReO\({}_{3}\)[38; 39], peroxometalates [40; 41; 42], biosourced metals [43] and one Lindqvist polyanion [44]. Although quite efficient, most of the cited processes are misaligned with the principles of green chemistry due to the experimental conditions, i.e., non-recyclable catalysts or toxic solvents or reagents. In our group, we develop organic-solvent-free strategies towards biomass vaporization, demonstrating the potential of oxo-molybdenum and oxo-vanadium coordination complexes and polyoxometalates (POMs) as oxidation catalysts for greener transformations [10; 12; 13; 14; 15; 16; 17; 18]. Notably, Keggin-type POMs, including [PMo\({}_{12}\)O\({}_{40}\)]\({}^{3-}\) and [PMo\({}_{11}\)VO\({}_{40}\)]\({}^{4-}\), offer tunable acidity and redox properties, making them particularly well-suited for oxidation reactions [19; 20; 21; 22; 23]. To improve recyclability, these catalysts have been heterogenized via ionic immobilization on solid supports like modified Merrifield resin [45; 46] or silica [47; 48], achieving recyclable catalytic systems for epoxidation reactions. Merrifield resin (**MR**), a chloromethylated polystyrene-based polymer, stands out as an ideal support due to its commercial availability, low cost, robustness and ease of functionalization, supporting POMs via ionic interactions and preventing leaching while enabling efficient recovery and reuse [49]. Our group has previously demonstrated the successful immobilization of POMs on this support [35], achieving recyclable catalytic systems for the epoxidation of cyclohexene into adipic acid [50].