Hydrophobic strong solid base derived from graphene oxide hybrid zirconium MOFs and its enhanced stability on furfural-MIBK aldol condensation to synthesize branched biofuel precursors

Aldol condensation between furfural (FA) and MIBK is used to synthesize branched bio-jet-fuel precursors. It remains difficult to design hybrid solid bases to efficiently promote this reaction, because only strong basic sites can activate MIBK. Different basic species were immobilized into zirconia/carbon hybrid supports by thermal decomposition of GO/UiO materials loaded with corresponding alkane (earth) nitrides. Only Cs immobilized zirconia/carbon (CsZC) could efficiently promote this reaction, while counterparts with Li, Mg and Ca species showed little activity over condensation between MIBK and FA. Optimized CsZC showed excellent FA conversion and selectivity towards desired products (88.6% in yields of FMIBK in 6 h at 130 °C). Two indirect proofs were provided to check the influence of basic strength on the catalytic performance, and only Cs samples had enough strong basic sites to accelerate the reaction. After modified with octyl groups, hydrophobic CsZC were reused for 4th cycle while retaining most of its original activity. Functionalization with organosilanes increased the hydrophobicity of the surface, which had dramatical promotion on activity, selectivity, and stability. It was the first time to run recycling experiments for this reaction, to afford the demands for chemical sustainability. Cs immobilized zirconia/carbon hybrid solid bases (CsZC) were synthesized by thermal decomposition of CsNO3 loaded GO/zirconium MOFs. CsZC could efficiently catalyze aldol condensation of furfural and MIBK to produce bio-jet-fuel precursors, and catalytic stability was greatly promoted by hydrophobic modification of CsZC with octyl groups. [Display omitted]