Poolman has made seminal contributions to the understanding of the dynamics and permeability of biological membranes and to the field of vectorial biochemistry, that is,  the role of electrochemical gradients in the fuelling and regulation of membrane transport. He demonstrated that the exchange of different sugars can be more advantageous for a cell than sugar-proton symport, and showed that cells exploit the coupling of substrate import to product exchange to conserve metabolic energy.
He is an expert in the field of ATP-binding cassette transporters, one of the largest known protein families, by combining functional and structural studies. Highlights include: discovery of export of hydrophobic compounds from the inner leaflet of the lipid bilayer; elucidation of sensing and gating mechanism of ABC importers involved in cell volume regulation; single-molecule fluorescence studies to elucidate the mechanism of solute capture and translocation; structural basis for peptide selection by receptors involved in nitrogen uptake; structural basis for vitamin recognition and transport by a new class of ABC importers; and the energy coupling stoichiometry of ABC importers.
Poolman has advanced of membrane transport by combining mechanistic in vitro studies with in vivo analyses of transporter regulation. His group has developed innovative technologies in membrane reconstitution and the probing of the physicochemical state of both the cytoplasm and the cell membrane. His group was the first to show that changes in the ionic strength are used to gate the activity of osmoregulatory transporters, providing the cell with a simple on/off switch to control its cytoplasmic volume. In parallel, his group developed sensors to quantify changes in ionic strength and excluded volume (macromolecular crowding).