Enhanced Methanol Formation over Cu/MgO Catalysts Derived from Mg-Rich Active Hydroxycarbonate Precursors

The quest for crystalline Mg-rich Cu precursors belonging to the rosasite/mcguinnessite family is challenging, leaving room for improvement and discoveries. Therefore, we investigated the synthesis of (Cu,Mg)2(OH)2CO3 precursors using a one-pot hydrothermal route, aiming to enhance Mg2+ incorporation and increase the efficacy of Cu/MgO catalysts towards CO2 hydrogenation to methanol. The first-principles formation energy calculations of (Cu1–xMgx)2(OH)2CO3 (x = 0.0, 0.125, 0.25, 0.375, and 0.5) shed light on the reduced structural stability observed in magnesium-rich phases, prompting us to validate these findings experimentally. Thus, the structure of the Mg-rich rosasite analogous to the mcguinnessite mineral (CuMg)2(OH)2CO3 was stabilized using a hydrothermal (HT) route and characterized thoroughly for the first time. Furthermore, the structure–activity relationship, physicochemical properties, and catalytic performance of the catalyst obtained via calcination of the mcguinnessite precursor were compared with conventionally prepared catalyst through coprecipitation (CP) and wet impregnation (IMP) routes. The experiments resulted in a CO2 conversion of 15.17%, a methanol selectivity of 68.49%, and a methanol STY of 98.11 mgMeOH·gcat–1·h–1 at 240 °C, 40 bar, and WHSV of 2600 mL/gcat·h using Cu/MgO-HT. In-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) revealed the essential intermediates present during the catalyst-mediated reaction that leads to methanol formation. Furthermore, due to the stabilization of active metal species preventing active metal agglomeration and sintering, Cu/MgO-HT demonstrates outstanding long-term stability in a 100 h run. DFT simulations were used to explain the promotional role of MgO-supporting Cu clusters, corroborating the findings of the experimental results.