  Bottom-up prepared carbon nanostructures appear as promising platforms for
future carbon-based nanoelectronics, due to their atomically precise and
versatile structure. An important breakthrough is the recent preparation of
nanoporous graphene (NPG) as an ordered covalent array of graphene nanoribbons
(GNRs). Within NPG, the GNRs may be thought of as 1D electronic nanochannels
through which electrons preferentially move, highlighting NPG's potential for
carbon nanocircuitry. However, the {\pi}-conjugated bonds bridging the GNRs
give rise to electronic cross-talk between the individual 1D channels, leading
to spatially dispersing electronic currents. Here, we propose a chemical design
of the bridges resulting in destructive quantum interference, which blocks the
cross-talk between GNRs in NPG, electronically isolating them. Our multiscale
calculations reveal that injected currents can remain confined within a single,
0.7 nm wide, GNR channel for distances as long as 100 nm. The concepts
developed in this work thus provide an important ingredient for the quantum
design of future carbon nanocircuitry.
