Facilitated charge transfer of stable multivariate transition Metal-organic frameworks for photocatalytic CO2 reduction

Metal-organic frameworks (MOFs) have drawn increasing attention in photocatalytic CO2 reduction, which are still hindered by limited photo-induced charge separation and unsatisfying stability. Fortunately, both superior stability and catalytic activity can be realized in multivariate transition metal-based MOFs by introducing conventional weak Lewis acids into strong Lewis acid clusters. However, most of the bimetallic and multimetallic titanium (Ti)-based MOFs are obtained by the post-modification or synthesis of polymetallic clusters in advance. The one-pot synthesis of stable multivariate Ti-MOFs for photocatalytic CO2 reduction is rarely reported. Herein, we developed a one-pot approach to combine Ti4+ with other metals to form a series of heterogeneous Ti-based MOFs ((PCN-250-Nn(n = 1,2...10)), including transition metals and Ti-based mixed metal-oxygen clusters. Compared to pristine monometallic PCN-250-Fe3, the chemical stability and catalytic activity of the PCN-250-Nn series have been greatly improved. The optimized PCN-250-N10 exhibited a CO yield of 39.35 mmol/g via photocatalytic CO2 reduction, which is superior to most reported related materials. Furthermore, the introduction of mixed metal oxygen clusters facilitates the electron transfer kinetics, enhances the activation of CO2, and reduces the reaction energy barrier, resulting in improved photocatalytic performance. This facile approach demonstrated here holds great potential for the design of efficient photocatalysts for solar-driven energy conversion.