  Biochars are an exciting class of environmental materials with a wide range
of applications, including carbon storage and sequestration, soil enhancement,
and pollution remediation. However, the limited knowledge of their molecular
structures and compositions and the lack of comprehensive understanding of the
relationship between these structures and biochars' diverse functionality, is
hindering advancements in their development. In this work, we further advance
the approach, first introduced by Wood et al. (2023), to constructing biochar
molecular models; and now include control of microporosity (pores < 2 nm size)
within the developed models. We construct biochar models representative of
woody biochars which are experimentally produced at 600 -- 650 oC highest
heating temperatures. Our models reproduce experimental H/C and O/C atomic
ratios, percentage aromatic carbon, true density, cumulative porosity, and pore
size distribution. The development of microporous biochar molecular models
allows us to identify the importance of chemical structures involved in the
assembly of biochar materials, and describe the relationship between these
structures and obtained micropores. To facilitate other researchers integrating
our approach into their work, we detail the steps taken, including the tests
and reasons for each decision, in the construction of the biochar models.
Furthermore, we share our developed molecular models in a format that can be
easily integrated into other group's work in the form of molecular dynamics
simulations.
