His research interests include organocatalysis, nanodiamonds (diamondoids), green chemistry, organic electronics, matrix isolation of reactive intermediates such as carbenes, and computational chemistry. He discovered the mechanism of tunnel control of reactions and demonstrated their diffusion, thus establishing a third driver of chemical reactions besides thermodynamic (energetically most favorable) and kinetic control (least barrier) (published in Science, 2011). He is one of the pioneers of organocatalysis, in which metal-containing catalysts are replaced by more environmentally friendly customized organic catalysts. Schreiner found a way to integrate nanodiamonds, which naturally occur in natural gas and petroleum but have nanoscale dimensions, into a coatings. In 1997 he helped develop the thiourea organocatalysis.