Cooperative catalysis of Co single atoms and nanoparticles enables selective CAr-OCH_(3) cleavage for sustainable production of lignin-based cyclohexanols

In this work,a dual-size MOF-derived Co catalyst(0.2Co_(1-NPs)@NC)composed of single atoms(Co_(1))and highly dispersed nanoparticles(Co NPs)was prepared by in-situ Zn evaporation for the highperformance conversion of lignin-derived o-methoxyphenols(lignin oil)to cyclohexanols(up to 97%yield)via cascade demethoxylation and dearomatization.Theoretical calculations elaborated that the dual-size Co catalyst exhibited a cooperative effect in the selective demethoxylation process,in which the Co NPs could initially dissociate hydrogen at lower energies while Co1remarkably facilitated the cleavage of the C_(Ar)-OCH_(3)bond.Moreover,the intramolecular hydrogen bonds formed in the omethoxy-containing phenols were found to result in a decrease in the bond energy of the C_(Ar)-OCH_(3)bond,which was more prone to be activated by the dual-size Co sites.Notably,the pre-hydrogenated intermediate(e.g.,2-methoxycyclohexanol from guaiacol)is difficult to undergo demethoxylation,indicating that the selective C_(Ar)-OCH_(3)bond cleavage is a prerequisite for the synthesis of cyclohexanols.The 0.2Co_(1-NPs)@NC catalyst was highly recyclable with a neglect decline in activity during five consecutive cycles.This cooperative catalytic strategy based on the metal size effect opens new avenues for biomass upgrading via enhanced C-O bond cleavage of high selectivity.

Functional zirconium phosphate nanosheets enabled transfer hydrogenolysis of aromatic ether bonds over a low usage of Ru nanocatalysts

Catalytic hydrogenolysis of aromatic ether bonds is a highly promising strategy for upgrading lignin into small-molecule chemicals,which relies on developing innovative heterogeneous catalysts with high activity.Herein,we designed porous zirconium phosphate nanosheet-supported Ru nanocatalysts(Ru/ZrPsheet)as the heterogeneous catalyst by a process combining ball milling and molten-salt(KNO_(3)).Very interestingly,the fabricated Ru/ZrPsheetshowed good catalytic performance on the transfer hydrogenolysis of various types of aromatic ether bonds contained in lignin,i.e.,4-O-5,a-O-4,β-O-4,and aryl-O-CH3,over a low Ru usage(<0.5 mol%)without using any acidic/basic additive.Detailed investigations indicated that the properties of Ru and the support were indispensable.The excellent activity of Ru/ZZrPsheetoriginated from the strong acidity and basicity of ZrPsheetand the higher electron density of metallic Ru0as well as the nanosheet structure of ZrPsheet.

Efficient lignin biodegradation triggered by alkali-tolerant ligninolytic bacteria through improving lignin solubility in alkaline solution

Low lignin solubility in aqueous solution is one of the major bottlenecks for lignin biodegradation and bioconversion.Alkaline solution contributes to improving lignin solubility,whereas most microbes can not survive in alkaline conditions.Herein,lignin dissolution behaviors in different pH solutions were systematically investigated,which indicated that solution pH above 10.5 contributed to high solubility of alkali lignin.To match with alkaline lignin aqueous system,several alkali-tolerant ligninolytic bacteria were isolated,most of which are distinct to previously reported ones.Then,the ligninolytic capabilities of these isolates were assessed in different pH conditions by determining their assimilation on alkali lignin,lignin-derived monomers and dimers,their decolorization capabilities,and their lignin peroxidase activities.Thereafter,the underlying ligninolytic and alkali-tolerant mechanisms of Sutcliffiella sp.NC1,an alkalophilic bacterium,was analyzed on the basis of its genome information.The results not only provide valuable information for lignin biodegradation and lignin valorization,but also expand knowledge on alkali-tolerant bacteria.