Riebesehl, FabianFabianRiebesehlAcikgöz, SerhanSerhanAcikgözMerbach, TimoTimoMerbachRoller, ChristianeChristianeRollerLumpp, DominiqueDominiqueLumppHerzog, DirkDirkHerzogAlbert, JakobJakobAlbertKelbassa, IngomarIngomarKelbassaSchlüter, MichaelMichaelSchlüterFiedler, BodoBodoFiedler2026-08-202026-08-202026-08-05Industrial and Engineering Chemistry Research 65 (30): 16002−16013 (2026)https://hdl.handle.net/11420/64428Due to their excellent thermal and electrical properties combined with pronounced porosity, carbon nanotube forests are promising as catalyst support materials for smart reactors. To maximize catalytic turnover, it is essential to increase the available surface while maintaining precise control over reactant flow and heat distribution. In this work, multiwalled carbon nanotubes are grown on three-dimensional substrates based on triply periodic minimal surfaces, which offer superior mechanical properties alongside controlled flow dynamics and enhanced heat transfer rates. The substrates are fabricated via laser powder bed fusion and subsequently coated using injection chemical vapor deposition. To evaluate the design limitations of the three-dimensional substrates for CNT growth, the impact of a decreasing permeability on the coating’s morphology is investigated. As the permeability decreases with the unit cell size of the triply periodic minimal surfaces and the introduction of an external wall, the characteristic CNT forest structure gradually transforms. Provided that permeability and precursor accessibility to the internal surfaces remain sufficiently high, the morphology and composition of CNT forests closely resemble those grown on flat substrates. Introducing the wall leads to a transition from vertically aligned CNT forests to horizontally oriented CNT networks due to enhanced laminar-like flow characteristics. While less dense, it offers an increased CNT quality. Below a critical minimal permeability, carbon nanostructures with numerous defects form. The successful coating and control of its morphology enable the utilization of the CNT for further smart tailoring of the reactor.en1520-50452026301600216013American Chemical Society (ACS)https://creativecommons.org/licenses/by/4.0/Technology::660: Chemistry; Chemical EngineeringJournal Article10.1021/acs.iecr.6c0112810.15480/882.1799510.15480/882.16831