Carbon nanomaterial supported single atom catalysts and methods of preparing same
Provided herein are single atom catalysts embedded in carbon nanomaterials and microwave assisted methods of preparing the same.
1. A method of incorporating at least one single atom transition metal catalytic site in a carbon nanomaterial,
the method comprising
(a) forming a mixture consisting of a metal organic framework (MOF), the carbon nanomaterial, and optionally a solvent, wherein:
the optional solvent is selected from the group consisting of ethanol and isopropanol;
the carbon nanomaterial is at least one selected from the group consisting of graphene, holey graphene, carbon nanotubes, carbon black, active carbon, graphyne, and graphdiyne; and
the MOF consists of a Zr 6 octahedron cluster and a transition metal-porphyrin complex of Formula I:
wherein:
R 1 and R 1′ are each independently selected from the group consisting of H,
C(═O)OR, C 1 -C 10 alkyl, and C 6 -C 10 aryl,
wherein each adjacent pair of R 1 and R 1′ independently optionally combines to form an optionally substituted phenyl ring, optionally substituted C 4 -C 8 cycloalkyl, or optionally substituted C 5 -C 8 cycloalkenyl ring (wherein the formed ring is fused to the pyrrole ring to which R 1 and R 1′ are attached),
wherein the C 6 -C 10 aryl and C 1 -C 10 alkyl are each optionally substituted with at least one substituent independently selected from the group consisting of OMe, and C(═O)OR;
each occurrence of R 2 is independently selected from the group consisting of H, C(═O)OR, C 1 -C 10 alkyl, and C 6 -C 10 aryl,
wherein the C 6 -C 10 aryl and C 1 -C 10 alkyl are each optionally substituted by at least one substituent independently selected from the group consisting of F, Cl, Br, I, CN, NO 2 , OMe and C(═O)OR,
each occurrence of R is independently selected from the group consisting of H and C 1 -C 10 alkyl; and
M is a transition metal; and
(b) subjecting the mixture to microwave irradiation to provide an irradiated carbon nanomaterial, whereby the irradiated carbon nanomaterial comprises at least one single atom transition metal catalytic site,
wherein the irradiated carbon nanomaterial is substantially free of transition metal aggregates.
2. The method of claim 1 , wherein the metal-porphyrin complex of Formula I is a metal-porphyrin complex of Formula III:
wherein:
R 1 and R 1′ are each independently selected from the group consisting of H, C 1 -C 10 alkyl, and C 6 -C 10 aryl,
wherein each adjacent pair of R 1 and R 1′ independently optionally combines to form an optionally substituted phenyl ring or optionally substituted C 4 -C 8 cycloalkyl or C 5 -C 8 cycloalkenyl ring (wherein the formed ring is fused to the pyrrole ring to which R 1 and R 1′ are attached),
wherein the C 6 -C 10 aryl and C 1 -C 10 alkyl are each optionally substituted with at least one substituent independently selected from the group consisting of F, Cl, Br, I, CN, NO 2 , and OMe;
each occurrence of R is independently selected from the group consisting of H or C 1 -C 10 alkyl; and
M is at least one transition metal selected from the group consisting of Cr, Mo, W, Mn, Tc, Re, Fe, Ru, Os, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, and Au.
3. The method of claim 2 , wherein at least one of the following applies:
(a) each occurrence of R 1 and R 1′ is independently H;
(b) each occurrence of R is independently H; and
(c) M is Cu or Fe.
4. The method of claim 1 , wherein the solvent is at least partially removed before subjecting the mixture to microwave irradiation.
5. The method of claim 1 , wherein the at least partial removal of solvent comprises heating the mixture to a temperature above about 78° C.
6. The method of claim 1 , wherein the microwave irradiation occurs with at least one of the following:
(a) an output power in the range of 150 to 300 W;
(b) a duration in the range of 3 to 30 seconds; and
(c) a frequency of 2.45 GHz.
7. The method of claim 6 , wherein the microwave irradiation occurs with at least one of the following:
(a) an output power of 300 W; and
(b) a duration of 5 seconds.
8. The method of claim 1 , wherein the microwave irradiation occurs in single mode.
9. The method of claim 1 , wherein the irradiated carbon nanomaterial comprises less than 5 percent transition metal aggregate by weight in the irradiated carbon nanomaterial.