Base-modulated synthesis of ZIFs for CO2 capture and conversion

The choice of organic base triethylamine (TEA) vs. 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and the synthetic approach (direct vs. two-step incorporation) significantly influences the crystal growth, particle morphology, porosity, and CO 2 reactivity of zinc imidazolate frameworks (ZIF-8 and ZIF-L). While the robust nature of these Zn-based MOFs allows retention of crystalline porosity upon base loading, testing under aqueous room-temperature conditions revealed contrasting catalytic behaviour across different reaction steps. Specifically, base incorporation boosted CO 2 capture and hydration into bicarbonate (carbonic anhydrase-like reactivity), reaching 4181 μmol HCO 3 - ·g -1 MOF for TEA-modulated ZIF-8 and 4.48 μmol HCO 3 - ·μmol -1 base for the best-performing DBU-based material, as well as CO 2 hydrogenation to formate species (formate dehydrogenase-like activity) and CO 2 fixation into cyclic ureas, achieving >50% yield with the DBU-modulated ZIF-8. These findings establish critical structure–activity relationships between framework stability, basicity localization, and multi-step catalytic performance, providing a clear roadmap for designing targeted MOF microenvironments for CO 2 conversion.