2.2 Cu/ZnO/Ti CMNR fabricated by flowing synthesis
The Ti membrane substrate was washed with the acetone, ethanol and
deionized water successively after being polished by the sand paper, in
order to remove the burrs, scratches, oil stains and impurities. Then,
the Ti membrane substrate was immersed in the sodium hydroxide solution
(10 mol·L-1) at 80 ℃ for 2 h, followed with dried at
80 ℃ for 2 h. After that, the Ti membrane substrate was modified by
3-aminopropyltrimethoxysilane (APTES), followed with Cu/ZnO
immobilization. A typical modification and assembly process was shown in
Figure 1: (1) The mixed solution of 95 wt% ethanol and APTES (8
g·L-1, 10 mL) 25 was permeating
through the Ti membrane substrate with the flowrate of 5
mL·h-1, then dried at 80 ℃ for 2 h, so that the
membrane was modified by APTES; (2) Zinc nitrate solution (0.845
mol·L-1, 5 mL) was permeating through the Ti membrane
substrate with the flowrate of 1 mL·h-1, followed with
dried at 80 ℃ for 2 h, so that Zn2+ was deposited in
the pores of Ti membrane substrate; (3) 2-methylimidazole solution
(2.151 mol·L-1, 5 mL) was permeating through the
membrane with the flowrate of 1 mL·h-1, and
coordinated with the Zn2+ deposited in the pores of Ti
membrane, and then, ZIF-8 was synthesized and immobilized in the pores
after being dried at 80 ℃ for 2 h; with repeating steps (2) and steps
(3) several times,the loading amount of ZIF-8 could be increased
effectively; (4) The ZIF-8/Ti membrane was washed with deionized water
for several times to remove the unstable particles, and then dried at 80
℃ for 2 h; (5) The copper nitrate solution (0.053
mol·L-1, 5 mL) was permeating through the ZIF-8/Ti
membrane with the flowrate of 1 mL·h-1, and the
Cu2+ was deposited stably and distributed uniformly in
the membrane pores by ion-exchange between Cu2+ and
Zn2+ in ZIF-8, followed with being dried at 80 ℃ for 2
h to form Cu2+/ Zn2+/Ti membrane;
(6) The Cu2+/ Zn2+/Ti membrane
obtained in step (5) was washed with deionized water and dried at 80 ℃
for 2 h to remove unstable particles; (7) Finally, the Cu/ZnO/Ti CMNR
fabrication could be accomplished by reduced under 20%
H2/N2 environment at 360 ℃ for 3 hours.
During this process, ZIF-8 has been taken as a sacrificial intermediate.
The above procedures from (1) to (6) were carried out in situ by
means of the technological apparatus as shown in Figure S1, and the
reduced and calcined procedure of (7) was achieved on the apparatus as
shown in Figure S2.
For convenient comparison, the Cu/Ti membrane was fabricated without
ZIF-8 as sacrificial intermediate, and the ZnO/Ti membrane was obtained
by directly sintering the ZIF-8/Ti membrane under the air atmosphere as
well.