A manganese bipyridine complex, Mn(bpydc)(CO)3Br (bpydc = 5,5'-dicarboxylate-2,2'-bipyridine), has been incorporated into a highly robust Zr(IV)-based metal-organic framework (MOF) for use as a CO2 reduction photocatalyst. In conjunction with [Ru(dmb)3](2+) (dmb = 4,4'-dimethyl-2,2'-bipyridine) as a photosensitizer and 1-benzyl-1,4-dihydronicotinamide (BNAH) as a sacrificial reductant, Mn-incorporated MOFs efficiently catalyze CO2 reduction to formate in DMF/triethanolamine under visible-light irradiation. The photochemical performance of the Mn-incorporated MOF reached a turnover number of approximately 110 in 18 h, exceeding that of the homogeneous reference systems. The increased activity of the MOF-incorporated Mn catalyst is ascribed to the struts of the framework providing isolated active sites, which stabilize the catalyst and inhibit dimerization of the singly reduced Mn complex. The MOF catalyst largely retained its crystallinity throughout prolonged catalysis and was successfully reused over several catalytic runs.

Postsynthetic exchange (PSE) of Ti(IV) into a Zr(IV)-based MOF enabled photocatalytic CO2 reduction to HCOOH under visible light irradiation with the aid of BNAH and TEOA. Use of a mixed-ligand strategy enhanced the photocatalytic activity of the MOF by introducing new energy levels in the band structure of the MOF.

Metal-organic frameworks (MOFs) with isolated metal-monocatecholato groups have been synthesized via postsynthetic exchange (PSE) for CO2 reduction photocatalyst under visible light irradiation in the presence of 1-benzyl-1,4-dihydronicotinamide and triethanolamine. The Cr-monocatecholato species are more efficient than the Ga-monocatecholato species.