Coating supported metal catalysts with ionic liquids (ILs) is a promising approach for controlling performance. Here, we report our results on a commercial supported nickel catalyst coated with 1-n-butyl-3methylimidazolium tetrafluoroborate, [BMIM][BF4], utilized for partial hydrogenation of 1,3-butadiene. Performance testing on the coated catalyst illustrates a record high selectivity towards partial hydrogenation (over 95% for butenes, irrespective of conversion level) ever reported on a supported nickel catalyst. Characterization provided direct evidence on electron donation from IL to nickel. Density functional theory calculations confirmed these results and showed that electron donation weakens the adsorption behaviour on nickel. Data indicated that binding strengths of butenes decrease more significantly than those of 1,3-butadiene does. This difference leads to increased selectivity towards partial hydrogenation. The filter effect confirmed by Conductor-like Screening Model for Realistic Solvents (COSMO-RS) calculations, on the other hand, helps to maintain this exceptional selectivity at all conversion levels by controlling active concentrations of 1,3-butadiene/butenes on nickel sites. (C) 2017 Elsevier Inc. All rights reserved.