Pentanoic esters are a new class of biofuels (additives) and are typically produced from biomass-derived levulinic acid/esters via hydrogenation-cyclization/ring-opening/ hydrogenation three-step transformations. Here, a one-step and atom-economic alkoxycarbonylation route is developed to produce pentanoic esters from widely available 1-butene. Based on the screening of 21 monophosphine and 26 diphosphine ligands, a Pd/ diphosphine ligand (bis(2-diphenylphosphinophenyl) ether, DPEphos) system gives 91% yield of linear and branched ethyl pentanoate (78/22 ratio) with a turnover number (TON) up to 26100 and demonstrates outstanding recycle potential. The apparent activation energy (E a ) of 1-butene alkoxycarbonylation in the presence of this catalytic system was estimated to be 89.4 kJ/mol via kinetic measurements. More importantly, homogeneously blending 10 vol % of the resultant esters in pure diesel can improve the low-temperature fluidity and pumpability of diesel and decrease the emission of exhaust pollutants of diesel without affecting the power performance of diesel engines. Compared with pure diesel, the CO, NO x , HC, and soot emission of blend diesel at 2500 rpm are reduced by 28%, 9%, 6%, and 42%, respectively. This work provides a promising route to produce high-performance fuel additive and simultaneously broadens the comprehensive utilization of C4 olefin.

Phosphine-containing porous organic polymers (phosphine-POPs) are a kind of potential catalyst support for alkene hydroformylation. However, the synthesis of phosphine-POPs with strong π-acceptor is still a challenge. Herein, we report the synthesis of phosphine-POPs with different π-acceptor properties [POL-P(Pyr)3, CPOL-BPa&PPh3-15, and CPOL-BP&PPh3-15] and evaluated their performances as ligands to coordinate with Rh(acac)(CO)2 for hydroformylation of alkenes. We found that the Rh center with stronger π-acceptor phosphine-POPs showed better catalytic performance. Rh/CPOL-BPa&PPh3-15 with strong π-acceptor bidentate phosphoramidites showed obviously higher activity and regioselectivity (TON = 7.5 × 103, l/b = 26.1) than Rh/CPOL-BP&PPh3-15 (TON = 5.3 × 103, l/b = 5.0) with weaker π-acceptor bidentate phosphonites. Particularly, the TON of the hydroformylation reached 27.7 × 103 upon using Rh/POL-P(Pyr)3 which possessed tris(1-pyrrolyl)phosphane coordination sites. Overall, our study provides an orientation to design phosphine-POPs for hydroformylation reactions.