TY - JOUR
T1 - Tuning UV Absorption in Imine-Linked Covalent Organic Frameworks via Methylation
AU - Dautzenberg, Ellen
AU - Lam, Milena
AU - Nikolaeva, Tatiana
AU - Franssen, Wouter M.J.
AU - van Lagen, Barend
AU - Gerrits-Benneheij, Ilse P.A.M.
AU - Kosinov, Nikolay
AU - Li, Guanna
AU - de Smet, Louis C.P.M.
PY - 2022/12/22
Y1 - 2022/12/22
N2 - Covalent organic frameworks (COFs) are porous materials with high surface areas, making them interesting for a large variety of applications including energy storage, gas separation, photocatalysis, and chemical sensing. Structural variation plays an important role in tuning COF properties. Next to the type of the building block core, bonding directionality, and linking chemistry, substitution of building blocks provides another level of synthetic control. Thorough characterization and comparison of various substitution patterns is relevant for the molecular engineering of COFs via rational design. To this end, we have systematically synthesized and characterized multiple combinations of several methylated and non-methylated building blocks to obtain a series of imine-based COFs. This includes the experimental assignment of the COF structure by solid-state NMR. By comparing the properties of all COFs, the following trends were found: (1) upon methylation of the aldehyde nodes, COFs show increased Brunauer-Emmett-Teller surface areas, reduced pore collapse, blue-shifted absorbance spectra, and 0.2 eV increases in their optical band gaps. (2) COFs with dimethylated amine linkers show a lower porosity. (3) In tetramethylated amine linkers, the COF porosity even further decreases, the absorbance spectra are clearly red-shifted, and smaller optical band gaps are obtained. Our study shows that methyl substitution patterns on COF building blocks are a handle to control the UV absorbance of the resulting frameworks.
AB - Covalent organic frameworks (COFs) are porous materials with high surface areas, making them interesting for a large variety of applications including energy storage, gas separation, photocatalysis, and chemical sensing. Structural variation plays an important role in tuning COF properties. Next to the type of the building block core, bonding directionality, and linking chemistry, substitution of building blocks provides another level of synthetic control. Thorough characterization and comparison of various substitution patterns is relevant for the molecular engineering of COFs via rational design. To this end, we have systematically synthesized and characterized multiple combinations of several methylated and non-methylated building blocks to obtain a series of imine-based COFs. This includes the experimental assignment of the COF structure by solid-state NMR. By comparing the properties of all COFs, the following trends were found: (1) upon methylation of the aldehyde nodes, COFs show increased Brunauer-Emmett-Teller surface areas, reduced pore collapse, blue-shifted absorbance spectra, and 0.2 eV increases in their optical band gaps. (2) COFs with dimethylated amine linkers show a lower porosity. (3) In tetramethylated amine linkers, the COF porosity even further decreases, the absorbance spectra are clearly red-shifted, and smaller optical band gaps are obtained. Our study shows that methyl substitution patterns on COF building blocks are a handle to control the UV absorbance of the resulting frameworks.
U2 - 10.1021/acs.jpcc.2c04586
DO - 10.1021/acs.jpcc.2c04586
M3 - Article
AN - SCOPUS:85143046636
SN - 1932-7447
VL - 126
SP - 21338
EP - 21347
JO - Journal of Physical Chemistry C
JF - Journal of Physical Chemistry C
IS - 50
ER -