Efficient charge separation by a donor-acceptor system integrating dibenzothiophene into a porphyrin-based metal-organic framework for enhanced photocatalytic hydrogen evolution

The high selectivity of organic ligands and metal ions that construct metal-organic frameworks (MOFs) enables considerable richness in the MOF structure and confers them with numerous potentials, rendering MOFs extremely interesting to researchers in the field of photocatalytic hydrogen evolution. However, the severe recombination of photoinduced charge carriers significantly restricts the photocatalytic performance of the MOFs. Herein, we report a porphyrin-based donor-acceptor (D-A) MOF consisting of meso-tetra(4-carboxyphenyl) porphyrin (TCPP) donor and a thieno [3,2b:20,30-d]thiophene-S,S-dioxide (BTDO) acceptor via coordination with Zn2+ ions, and denoted as TCPP-Zn-BTDO. The charge-transfer interaction from TCPP to BTDO broadened the light absorption range of TCPP-Zn-BTDO, with a high theoretical spectral efficiency of 69.72%. The D-A structure of TCPP-Zn-BTDO effectively enhanced the internal electric field because of its large molecular dipole, which significantly improved the charge-separation efficiency. Based on the aforementioned improvements, TCPP-Zn-BTDO showed a three-fold higher photocatalytic hydrogen evolution rate than the corresponding monocomponent MOF of TCPP-Zn without the BTDO acceptor. The D-A MOF reported in this study provides a new strategy for enhancing the photocatalytic performance of MOF.