Systematic and Dramatic Tuning on Gas Sorption Performance in Heterometallic Metal–Organic Frameworks

Despite their having
much greater potential for compositional and
structural diversity, heterometallic metal–organic frameworks
(MOFs) reported so far have lagged far behind their homometallic counterparts
in terms of CO2 uptake performance. Now the power of heterometallic
MOFs is in full display, as shown by a series of new materials (denoted
CPM-200s) with superior CO2 uptake capacity (up to 207.6
cm3/g at 273 K and 1 bar), close to the all-time record
set by MOF-74-Mg. The isosteric heat of adsorption can also be tuned
from −16.4 kJ/mol for CPM-200-Sc/Mg to −79.6 kJ/mol
for CPM-200-V/Mg. The latter value is the highest reported for MOFs
with Lewis acid sites. Some members of the CPM-200s family consist
of combinations of metal ions (e.g., Mg/Ga, Mg/Fe, Mg/V, Mg/Sc) that
have never been shown to coexist in any known crystalline porous materials.
Such previously unseen combinations become reality through a cooperative
crystallization process, which leads to the most intimate form of
integration between even highly dissimilar metals, such as Mg2+ and V3+. The synergistic effects of heterometals
bestow CPM-200s with the highest CO2 uptake capacity among
known heterometallic MOFs and place them in striking distance of the
all-time CO2 uptake record.