| Extended 3D macroporous structures (Section 2) |
NPs, preformed and/or nucleated in situ, are incorporated
at different stages (before, during, or after) of the colloidal templating
step(s) to fabricate the macroporous support structure |
NP and support formation steps are entirely decoupled from
each other for independent tuning and optimization at different length
scales |
Choice of NP incorporation before, during, or after colloidal templating
step(s)
has a pronounced impact on the final NP stability and accessibility
(Section 2.1) |
| Well-defined and interconnected porosity facilitates
investigation
into physical transport properties, and the extrapolation of such
results from the single pore level to the macroscopic level |
RCT method (NP incorporation during colloidal
templating) provides high thermomechanical stability and accessibility
due to partial NP embedding within the support matrix (Section 2.2) |
| |
| Extended hierarchical macro-mesoporous structures
(Section 3) |
Secondary mesoporous structure is created with, or after, the
primary macroporous structure is formed |
Hierarchical
macro-mesoporosity creates additional surface
areas for mass transport of reactants and products |
Creating
such complex structures necessitates spatially independent
template removal and pore functionalization steps, which inadvertently
increases synthetic complexity (Section 3.1) |
| NPs, preformed and/or nucleated in situ, are incorporated before, during, or after each colloidal templating step(s) |
Mesoporosity unlocks
size- and shape- selective catalytic properties
found only in anomalous and confined Knudsen diffusion regimes, whereas
unconfined catalysis can occur on large surface areas of macropores |
With orthogonally functionalized templating colloids
and solvents (e.g., polar and nonpolar), together with judicious NP
size selection, spatially disparate active site functionalization
and consequently, compartmentalization, have been achieved (Section 3.2) |
| Reactant transport is predefined in such hierarchical
porous
structures (bulk ↔ macropores ↔ mesopores), which can
be exploited for selective catalytic cascades |
| |
| Discrete hollow nanoreactors (Section 4) |
Individual colloidal particles of various
shapes as standalone
sacrificial templates for additional material shell growth |
Standalone template affords the greatest synthetic
flexibility among all three structures: anisotropic and precisely
tailored templates have been exploited to compartmentalize active
sites and prescribe reactant flow within nanoreactor structures |
The design challenge (and opportunity) is to not
only compartmentalize incompatible active sites, but to also synergize
the different active sites (via engineering active site proximity)
to achieve catalytic outcomes beyond the sum of its individual parts
(Section 4.1) |
| NPs can be incorporated before, during, or after each colloidal templating
step(s) |
