1. A possible solution: Flexible porous materials
Materials that switch from closed to open
Rigid Porous Materials
Switching Porous Materials
Working capacity always <uptake for rigid materials
But only one flexible material has potential capacity better than CNG
But most flexible materials are irreversible 1

2. Isotherm types of flexible porous materials
Yet to be classified by IUPAC
Rigid MOMs
Gradual
(Open to more open)
Sudden
(Open to more open)
2nd cycle
Type F-V
1st cycle
Gradual
(Close to open)
Sudden
(Close to open)
Shape Memory
See Q. Y. Yang, et al., Angew. Chem. Int. Ed. 2018, 57, 5684. 2

3. Potential applications
Literature Survey of flexible porous materials
only ca. 130 examples
Total
Structural
changes
Typical examples
Potential applications
Type F-I 71
Open to more open
(gradual)
MIL-53
Cu(aip)(H2O)
Separation
Type F-II 15
(Sudden)
Cu(bpy)2(OTf)2
(ELM-12)
Type F-III 16
Closed to open
Zn(ndc)(o-phen)
Zn2(bdc)2(bpy)
Type F-IV 29
ELM-11
Co(bdp)
X-dia-1-Ni
Storage
Type F-V 2
Open to more open (1st)
No phase change (2nd)
Cu2(bdc)2(bpy)
X-pcu-3-Zn-3i
Memory effect 3

4. Type F-IV isotherm exhibited for methane
Only 2 materials meet high uptake criteria for ANG
Co(bdp)
X-dia-1-Ni
X-dia-1-Ni-a1
X-dia-1-Ni-c1
P-DSC
J. R. Long, et al., Nature, 2015, 527, 357; Q. Y. Yang, et al., Angew. Chem. Int. Ed. 2018, 57, 5684. 4

5. sql-1-Co-NCS Type F-IV isotherms also exhibited by layered materials
The layered packing of the (A) closed (guest-free) and (B) CO2- loaded phases of sql-1-Co-NCS.
Recyclability test at 273 K.
(A) N2 (77 K) and CO2 (195 K) sorption isotherms for sql-1-Co-NCS. (B) High-pressure CO2 sorption isotherms for sql-1-Co-NCS collected at 253, 265, 273, 283 and 298 K.
S.Q. Wang, et al., Chem. Commun., 2018, 54, 5

6. Sorption 501: finding the right material
First we need the right haystack, then the right material 6

7. So many haystacks 7 Hybrid Ultramicroporous Materials
Porous Molecular Crystals
Metal Organic Cages
Zeolites
Covalent Organic Frameworks
Porous Molecular Glasses
Polymer Networks
Porous Organic Cages
Metal Organic Frameworks
Hydrogen-Bonded Organic Frameworks (HOFs)
Periodic
Mesoporous Organosilica (PMO)
Porous Organic
Polymers (POPs)
Nanoparticles (e.g. FeO)
Porous Ceramics 7

8. The Solution?
Taxonomy
The “chemistree”
of sorbents 8

9. Take home messages
Keep it simple – pure crystalline materials from readily available, safe molecular building blocks = platforms
Pore size should match target: <0.4 nm for CO2; >1.5 nm for crystalline sponges
Pore chemistry should match target: inorganic anions for CO2, CO, Xe, NOx, SOx (HUMs); hydrocarbons for NG (MOMs); supramolecular synthons (cocrystals)
Modeling, database mining and in situ SCXRD afford critical insight
There is more to life than carboxylic acids and carboxylate anions
Small structure/chemistry changes can have a big effect
New highs for Qst towards CO2, Xe, C2H2 and CH4
Selectivity benchmarks: CO2/N2, C2H2/C2H4, CO2/C2H2, CO2/CO, Xe/Kr
Better solubility, stability and bioavailabilty of drug substances without new chemistry
These improvements are more than incremental 9

10. Think Supramolecularly10