Ternary Inclusion Co-Crystals for Efficient Photothermal Conversion and Solar-Driven Water Evaporation

Organic co-crystal engineering offers a convenient and efficient platform for preparing photothermal conversion (PTC) materials. However, current donor-acceptor (D-A) co-crystals generally have medium photothermal performance. Here, an inclusion co-crystal strategy is presented, i.e., host-guest encapsulation of small acceptor inside donor-type macrocycle's cavity, to enhance PTC efficiency through the promotion of D-A binding. A naphthyl-sidewall Tröger's base (TB[2]) molecular box donor is elaborately designed, which can encapsulate electron-deficient 7,7,8,8-tetracyanoquinodimethane (TCNQ) to form a 1:2 ternary inclusion charge-transfer (CT) co-crystal via the synergism of multiple noncovalent forces. Under 808 nm laser irradiation (0.7 W cm^-2), the PTC efficiency of co-crystals is as high as 94.3%. The co-crystals are further introduced into the porous polymer of polyurethane (PU) to prepare an interfacial evaporator (TB-TCNQ@PU) for solar-driven water evaporation. Under 1 Sun irradiation, a high-water evaporation rate of 1.746 kg m^-2 h^-1 and a prominent solar-to-vapor efficiency of 93.8% are achieved. This work opens new avenues for the efficient PTC materials.