  We synthesized a pure organic non-metal crystalline covalent organic
framework TAPA-BTD-COF by bottom-up Schiff base chemical reaction. And this
imine-based COF is stable in aerobic condition and room-temperature. We
discovered that this TAPA-BTD-COF exhibited strong magneticity in 300 K
generating magnetic hysteresis loop in M-H characterization and giant chimol up
to 0.028. And we further conducted zero-field cooling and field-cooling
measurement of M-T curves. The as-synthesized materials showed a large chi/mol
up to 0.028 in 300 K and increasing to 0.037 in 4.0 K with 200 Oe measurement
field. The TAPA-BTD-COF 1/chimol~T curve supported its ferrimagnetism, with an
intrinsic delta temperature as -33.03 K by extrapolating the 1/chimol~T curve.
From the continuously increasing slope of 1/chimol~T, we consider that this
TAPA-BTD-COF belongs to ferrimagnetic other than antiferromagnetic materials.
And the large chimol value 0.028 at 300 K and 0.037 at 4.0 K also supported
this, since common antiferromagnetic materials possess chimol in the range of
10-5 to 10-3 as weak magnetics other than strong magnetic materials such as
ferrimagnetics and ferromagnetics. Since this material is purely non-metal
organic polymer, the possibility of d-block and f-block metal with
unpaired-electron induced magnetism can be excluded. Besides, since the COF
does not involve free-radical monomer in the processes of synthesis, we can
also exclude the origin of free-radical induced magnetism. According to recent
emerging flat-band strong correlated exotic electron property, this
unconventional phenomenon may relate to n-type doping on the flat-band locating
in the CBM, thus generating highly-localized electron with infinite effective
mass and exhibiting strong correlation, which accounts for this non-trivial
strong and stable ferrimagneticity at room-temperature and aerobic atmospheric
conditions.
