Owing to their high porosity and tunability, porous solids such as metal–organic frameworks (MOFs), zeolites, or activated carbons (ACs) are of great interest in the fields of air purification, gas separation, and catalysis, among others. Nonetheless, these materials are usually synthetized as powders and need to be shaped in a more practical way that does not modify their intrinsic property (i.e., porosity). Elaborating porous, freestanding and flexible sheets is a relevant shaping strategy. However, when high loadings (>70 wt.%) are achieved the mechanical properties are challenged. A new straightforward and green method involving the combination softwood bleached kraft pulp fibers (S) and nano-fibrillated cellulose (NFC) is reported, where S provides flexibility while NFC acts as a micro-structuring and mechanical reinforcement agent to form high loadings porous solids paper sheets (>70 wt.%). The composite has unobstructed porosity and good mechanical strength. The sheets prepared with various fillers (MOFs, ACs, and zeolites) can be rolled, handled, and adapted to different uses, such as air purification. As an example of potential application, a MOF paper composite has been considered for the capture of polar volatile organic compounds exhibiting better performance than beads and granules.