Microwave-induced preparation of MgO-loaded N-rich porous biochar from marine biomass for efficient CO₂ capture and mechanism exploration via theoretical calculation

For enhancing the prospects of solid adsorbents based on biochar for CO2 capture, a simple and green method (without modifying and pore-forming agents) for preparing MgO-loaded N-rich porous biochar (MgO/NBC) was constructed by microwave-induced marine biomass (Enteromorpha), then the CO2 adsorption mechanism was explored by theoretical calculations. The results showed that microwave heating promoted the development of graded porous structure, the formation of alkaline N-containing species, and the loading of MgO with smaller grains of MgO/NBC to exhibit better CO2 capture performance with a synergistic mechanism of physical and chemical adsorption. The maximum CO2 adsorption capacity of MgO/NBC was 4.79 mol kg-1, and the CO2/N2 selectivity and CO2/O2 selectivity were 79.83 and 11.14, respectively. After 15 cycles, the loss of adsorption capacity of MgO/NBC was 14.61%, which showed good cycling performance. DFT calculations showed that the heterogeneous structure between pyridine N and MgO enhanced the CO2 capture performance by enhancing the affinity and electron transfer between MgO/NBC and CO2 to reduce the adsorption energy. This work provided new insights for the construction of simple, green, low-cost, and high-efficiency CO2 solid adsorbents to help CO2 reduction.