Band Alignment Modulation in In-Oxo Metal Porphyrin SURMOFs for Bulk Heterojunctions Photovoltaics

Tailoring band alignment at donor–acceptor interfaces is critical for optimizing charge separation and exciton dynamics in optoelectronic materials. Herein, we present a first-principles study of Indium-oxo SURMOFs based on tetratopic free-base and metalated porphyrin (TCPP) linkers, where band edge positions are systematically tuned via porphyrin core metalation without altering the crystal structure. Using DFT and sTDA calculations, we evaluate electronic structure and optical absorption properties across a library of metal centers (H+, Ni2+, Zn2+, Pd2+, Pt2+, [In(OH)2+]). By combining distinct linkers within a periodic simulation cell, we construct model heterostructures that exhibit either type-I or type-II band alignment, enabling exciton confinement or spatial charge separation, respectively. Furthermore, multi-heterojunction configurations incorporating three different metal centers demonstrate the feasibility of constructing energy cascades for directional exciton funneling and controlled charge extraction. These results establish porphyrin metalation as a modular strategy for engineering band offsets in SURMOF-based heterostructures for photochemical and optoelectronic applications.