An ultrastable La-MOF for catalytic hydrogen transfer of furfural: <i>in situ</i> activation of the surface

Abstract

The poor stability of metal-organic frameworks (MOFs) severely limits their catalytic application. The <i>in situ</i> activation of stable MOF catalysts not only simplifies the catalytic process, but also reduces energy consumption. Therefore, it is meaningful to explore the <i>in situ</i> activation of the MOF surface in the actual reaction process. In this paper, a novel rare-earth MOF La₂(QS)₃(DMF)₃ (LaQS) was synthesized, which exhibited ultra-high stability not only in organic solvents but also in aqueous solutions. When LaQS was used as a catalyst for the catalytic hydrogen transfer (CHT) of furfural (FF) to furfuryl alcohol (FOL), the FF conversion and FOL selectivity reached 97.8% and 92.1%, respectively. Meanwhile, the high stability of LaQS ensures an enhanced catalytic cycling performance. The excellent catalytic performance is mainly attributed to the acid-base synergistic catalysis of LaQS. More importantly, it has been confirmed by control experiments and DFT calculation that the <i>in situ</i> activation in catalytic reactions leads to the formation of acidic sites in LaQS, together with the uncoordinated oxygen atoms of sulfonic acid groups in LaQS as Lewis bases, which can synergistically activate FF and isopropanol. Finally, the mechanism of <i>in situ</i> activation-caused acid-base synergistic catalysis of FF is speculated. This work provides meaningful enlightenment for the study of the catalytic reaction path of stable MOFs.