In this work, H3PMo12O40 (PMo) and CS2.75H0.25PMo12O40 (CsPMo) were modified via the polymerization of tetrahydrofuran (THF), followed by thermal treatment to be used as model catalysts for the oxidative dehydrogenation of isobutyric acid (IBA) into methacrylic acid (MAA). The THF-treated catalysts retained partially reduced stable structures with high surface areas. The THF-treated catalysts showed higher IBA conversions acid MAA yields than the corresponding mother catalysts. The THF-treated CsPMo catalyst showed the best catalytic performance among the catalysts tested. It is concluded that the high surface area, the suitable acidity, and the partially reduced stable structure of the THF-treated CsPMo catalyst were responsible for this catalytic performance.