MOF-derived synthesis of MnS/In2S3 p-n heterojunctions with hierarchical structures for efficient photocatalytic CO2 reduction

Photoreduction of CO2 to valuable fuels with semiconductor photocatalysts is a good solution to the problems of global warming and energy crisis. Creation of hybrid nanomaterials with hierarchical and/or heterojunction structures is beneficial to develop efficient photocatalysts for CO2 reduction. Herein we present a convenient method to obtain a hybrid photocatalyst consisting of MnS and In2S3 nanosheets with assembled hierarchical structures through using Mn2+-loaded MIL-68(In) submicro-rods as templates. Owing to the dispersive Mn2+ and In3+ ions in templates, numerous small p-n heterojunctions of MnS/In2S3 could be simultaneously produced in each hierarchical particle. The p-type MnS and n-type In2S3 with an original type II band alignment can create a stronger built-in electric field after the formation of p-n heterojunctions, which is favorable for charge separation and migration to catalyst surface. The prepared MnS/In2S3 heterojunctions show an 4-fold higher photocatalytic activity toward CO2 reduction than pristine MnS and In2S3. The MnS/In2S3 hierarchical structures were well characterized and their working mechanism was explored. This work demonstrates a facile strategy to create efficient hybrid photocatalysts with both hierarchical structures and p-n heterojunctions for photocatalytic applications.